QB Express: Issue #10

Letters

Letter From MystikShadows

Hi Pete,

Well, a wise man once said, he who reads QB Express #9 shall find find himself enlightened and enriched. Hmmm I think that it was me who said that to the wise man...;-). Every time I know QB Express is to release a new issue, I jump into what I like to affectionately call, my "Johny 5 is alive" mode. I need, want and crave input, information, you name it. lol. And so far, QB Express has always answered that call of the binary wilderness successfully, taming down the beast within me that needs to read, learn, acquire new knowledge, solve problems and the likes. After reading #9, I'm calmer now, I've finally managed to sleep some, cut down on half the caffeine intake I've been having anticipating the arrival of #9. QB Express' #1 fan you say, YES INDEED ;-) and I hold that title with great pride (and selfish joy might I add). But realistically, I don't print all my articles so I have to humbly accept position #2 and give position #1 to Lurah ;-). As the saying goes "Anticipate denotes intelligence" Quoted from "The 5th Element", if that's so, then for about a week's time around each release of QB Express, I'm as brilliant as I can get ;-). lol

As far as the Number one contributor, well I've been pondering that ;-). Sure I can submit alot of stuff, there's still plenty I haven't written yet, and will be writing. But due to the nature of the tutorials I present, and in relations to QB Express' orientation (although that is changing too, more on that later in this letter ;-). I'm not sure all that I submit qualifies as true QB Express material. What I've seen in QB Express is that it is a game oriented magazine. the Qmunity is indeed one of game development. I haven't seen many accounting systems, databases management systems, word processors applications and other "business related or commercial software related" stuff in QB Express or anywhere else in Qmunity.. However, I do think that what I submit is good stuff as far as it's quality goes. But as far subject matter, for the game developers out there in the Qmunity some might wonder what my submissions are doing there as in how do they related to their projects. My programming background isn't from the gaming world (although I do have a game in the making ;-) it is my first attempt at a game. My background is more in the business application and commercial application development level. From that background comes some knowledge that I feel is important to share to those game programmers that might want to add a bit to their game. Sure some of what I cover may seem out of bound to the Qmunity...As I told you before, I like to cover the boring part of programming. Why? because to any programmer, game or otherwise, I think they can benefit from the submissions I have made and if I can make the boring side at least a bit less boring by the way I teach it, then I call that a successful submission. I believe I'm the only one that covers that side, it's a dirty job, but somebody's gotta do it. I can't make a 3D space ship do it's thing, but I can make sure it does it well, all the time ;-). It's that side that I offer to Qmunity the behind the scene side. Whether the game is to be of personal, Qmunity or even commercial value, I think that what I mention in my tutors and articles are worth reading just to help the developers at least think about a few things just to help their games get the edge.

I totally agree with Lachie Dazdarian, the articles he liked were as fascinating and brilliant as he puts it. One thing about Lurah that I can say is that maybe english isn't is native tongue, but his convictions and ideals are very strong and well founded that makes him more than credible for any discussion/debates about what he likes to talk about :-) and with his game, Tales form Argania in the making he'll be proving that everything that he believes in, is indeed, true. :-) (no pressure there Lurah right? lol). Lurah is a very realistic and down to earth kinda person, he'll tell things how they are, even bluntly if he has to, to get his point across some might find that his point is usually right too. I could also relate, in a non game fashion, to "What QB means to me". although I started coding long before QB, heck long before any basic lol. the situations he mentions were still there back then. Very insightful and nostalgic in some way, at least to me ;-).

I have at least 3 other submission ideas, 1 of which will probably be a series, once again...so I'm far from done writing articles and such...as I told you before, these require coding before I go ahead and write about them...so since I have submissions a plenty for the upcoming issues, I got in coding mode, get these things done so I can write about them ASAP :-). So don;t worry Qmunity, there's plenty of boring stuff to talk about ;-). But I think that you'll agree that in programming, just like in math, two negatives really do make a positive ;-). Remember what I told you about the Qmunity growing and focusing and such, projects emerging and the likes in my last letter? Well I think the reviews and projects you talk about in #9 is already a good proof of that. Games are awesome, and there's till people coding tools for game makers, basically, it's always great to see all this happening. Makes me wish I was in the QB community from day one so I wouldn't have missed a single moment of it. I mean don't get me wrong, I was in the community as in I was a QB coder in it's very start and all, but I was never online, didn't know there were groups forming and all since about 10 or 11 months ago...so I missed alot :-). But I'm glad to be here now :-).

I'd like to commend Rattrapmax6, his horse humor was much better this time around. Oh and you should see is 400x400 scolling text map editor he's working on, there's something for QB Express #10 for sure you can read about it here: http://textworld.adaworld.com/forum/viewtopic.php?t=51&start=0 and awesome piece of work if I do say so myself. Umm errr, I just did didn't I? ;-).

Thank you so much for announcing our competition on http://www.ascii-world.com in QB Express. I don't know about the others, but I'm sure, in advance, that any success this competition has will be greatly thanks to you and QB Express and whatever forum we'll announce it on ;-). I for one hope that it will be a great success.

Congratulations again Pete for continuously outdoing yourself in the way things are organized and presented in every issue, like Lachie said your positive approach to the Magazine, the Qmunity and the humor make QB Express the success it is. oh and the contributors of course have 50% of the honors :-).

And now that I've made this letter as big as my average article, I'll stop ;-)...

Signed, the number one errr two Fan ;-).

MystikShadows
Stephane Richard
http://www.ascii-world.com

Thanks again for all the kind words, man! I agree with you that the Qmunity is mostly a game programming community -- but there are many people interested in non-gaming types of programming as well. GUIs, for example, or graphics demos. Just look at this issue -- we have a GUI tutorial and Adigun's running a FB graphics demo competition. Plus, business / professional program development is a very important skill to have if you ever want to get a legit programming job. I'm glad to run those tutorials!

There are no ifs, ands or butts about it, you're still the most dedicated and productive writer that QB Express has. Every month you submit three to four tutorials, a letter to the editor, some announcements, etc. Truly remarkable. Without people like you, I couldn't pull this magazine off.

-Pete

Letter From Jacob Palm

Hi Pete Berg!

First of all, I'd like to say that I read every single article in every single issue of QB Express. It's simply the best QB zine ever, no doubt!

Well, I'm kind of a GUI-guy, so I was wondering if the magazine could have some GUI related stuff? I'd be more than happy to contribute with some reviews, tutorials etc.

Keep up the good work with QB Express and Pete's QB site!

Jacob Palm

JacobPalm.dk

QB Express has had quite a bit of GUI stuff in the past, if I do say so myself: a two-part series on QB GUI programming by VonGodric (Issue #3 & #5) - on buttons and textboxes, and a two-part FB GUI series by Nekrophidius that ran in Issue #6 & #7. But obviously, that's not meeting the demand. :)

Therefore, I encourage anyone with knowledge in GUI programming that's interested in writing to buckle down and write an article or tutorial for QB Express. Clearly there's a captive audience! If you want to write but don't have a topic, GUIs are a great place to start.

Anyway -- shortly after he sent this letter in, Jacob sent me an article on QBasic GUI Development. So it looks like he's taking up his own suggestion.

-Pete

Letter From aetherFox

Hey Pete,

Excellent work on QB Express #9. As usual, it was a good read on the most part, and I wanted to commend you for the excellent job you did (and have been doing, and will do) in keeping the magazine in what generally is excellent shape.

My biggest problem is that it doesn't render properly in Firefox, which is a shame because I think a lot of people in the community use that browser. I am sure it is a simple fix, running the CSS through the W3C compliance check should tell you what is wrong.

It's nice to see that some people appreciate what na_th and I have done, and it's awesome to see that the game was well recieved by some people. While Joseph's review was information-wise terribly flawed, both na_th_an and I recieve criticism well; however it is a little pointless to review a text adventure game when you clearly don't seem to enjoy them. Nevertheless, Los Monos del Obús is cooking something pretty interesting for out next release. I'll be writing you an article this next issue hopefully, I have exams coming up and time is kind of sparse, but I'll do what I can.

Keep up the excellent work,
Avinash Vora a.k.a. aetherFox
http://avinash.apeshell.net

I know all about the FireFox errors. The CSS is valid, but FireFox has a bug (something to do with its Gecko engine) that causes it to put big gray boxes everywhere. (That's probably what you're talking about.) I've been searching for a long time to find a better solution to this problem, but I've yet to come across one that works better than the current solution. So if there are any CSS geniuses out there that know of a better way to make textboxes that are both Pre-formatted and have text wrapping -- let me know!

About Joe's review -- I know that it was intentionally biased, since he wrote it right after you two had your flame war at QBNews. He later admitted that his review was intentionally close-minded and harsh -- and then he claimed it was a joke. (I say "claimed" since nobody really found it all that funny...) There was a huge discussion about this in the QBasic News thread that I would reprint some quotes from, but since Wildcard shut down QBN it is now no longer available. So I say we just let the issue rest.

Thanks for the letter -- and I'm glad you and Na_th_an handled Joe's negative review so well.

-Pete

Letter From nitro2k01

Why the heck do you have that pikachu guy as a favicon?

/nitro2k01

That icon isn't Pikachu...but it sure looks like him. :)

It's actually an "Electric Rat" from DarkDread's The Secret of Cooey 2. When I redesigned my site, I decorated it with sprites from popular QB games that had been reviewed on my site in the past. Since DarkDread's Electric Rat was the perfect size (16x16 pixels, I believe), and I liked the picture, I made it my favicon.

Look here: Secret of Cooey 2 Review

-Pete

Letter From anarky

Where are they now?

Last month's WATN article promised an interview with Eric Cowles, better known as 1000101. I have unfortunately not been able to interview Eric before the deadline. After posting on the forums, and emailing a nunber of people, I received two interested parties. DarkDread and Gianfranco of QBGames. DarkDread isn't online at the time of writing the article, and I have not been able to get him at a point where he is not too busy. Gainfranco emailed me recently, but since I have only just received the letter, I have insufficient time to compose the article. Therefore, in issue 11 of QBExpress, expect another interview by either one of the three people above. Apologies for the inconvenience.

>anarky

Hey man, no problem at all. You don't even need to apologize. If you can't meet the deadline, your article can just wait for next month. Or even better - you could do two interviews for the next issue to make up for it. :)

-Pete

Have a letter for the editor? Send all your rants, raves, ideas, comments and questions to pberg1@gmail.com.

News Briefs

News from all around the QB community, about the latest games, site updates, program releases and more!

Site News

The QBasic News Debacle

QBasic News was shut down yesterday for absolutely no good reason, and it REALLY pisses me off. That forum was the best collection of QBasic help, tutorials, questions, answers, news, debate, information and just good ol' conversation in the history of the QBasic scene. It is an irreplacable resource and historical document, and if it is not restored, the community made up of 1650 users -- and almost 100,000 messages will be lost forever. And according to Wildcard, it's NOT coming back. Nobody really knows exactly what happened except for Wildcard. For now, I'm not even gonna try to explain it. I guess he just snapped.

NOTE: I had a much longer news report planned for this, but I've run out of time and have to leave a on an extended 4-day trip. When I return I plan on doing a special update to QB Express #10 to give you the full story (or as much of it as I can find). Until then, I leave you with this news report, courtesy of the ASCII-WORLD guys:

UPDATE (5/31): Well, now that I'm back from my trip it looks like the whole QBasic News thing has blown over. Wildcard restored the site in full over the weekend and then announced his retirement from QBasic News. Although the site is restored, however, the damage has already been done. The once thriving community has been diffused over a half dozen new or recovering QB/FB forums, and QBasic News is now missing the majority of its active and respected senior members. The new owner of the website is Sumo Jo, the guy behind Quickhost and Freebasic.tk. Hopefully he will be able to restore QBasic News to its former glory, but I don't see it happening anytime soon. So much can change in just a matter of days.

QBasicNews, What the ... ?

A Newsbrief by MystikShadows and Lurah

Where to begin, not sure, but the most established online forum to our beloved QB Community, QBasicNews has come to a harsh, unpredictable, definitaly avoidable end, in my most humble opinion. From what i've seen, it would seem many posts aimed at helping were misread or simply disregarded, some jumped to conclusions they shouldn't have, hell almost broke loose, next thing you know a post about "QbasicNews is shutting down" surfaces.

How did it all happen? on the surface and from what users can read, it seems that what started out as a thread about a competition, ended as a public debate about what's doing (or not doing) what to help make QBasicNews a better place. After a few exchance of ideas/criticism/suggestions/comments WildCard seemed to have decided to close the boards. In my opinion this decision was absolutely uncalled for and was the result of either the powers that be are unable to accept criticism of any kind (thinking they are above it or something, yeah right). or the admin, WildCard, was looking for a way out of QBasicNews and decided that that thread that started a debate was going to be his way out. in both cases, it just doesn't make sense and showed the immaturity of the board administrator(s).

All I know is that the comments that were made, most of them were to help and give tricks and tips about what could be done, not just by my but by others, in their own special way ;-). But it seems the admins and mods had a very different concept of what a moderator and administrator should do or have to do. All this lead to what we can read now on QBasicNews.

From the quick time it took to come to the decision to close this board, all I can think is those two reasons I mentionned. No other reason would cause such a quick reaction of this nature.

MystikShadows and Lurah

http://www.ascii-world.com

QB Forum Wrap-Up

There have been about a trillion new QB forums started within the last 24 hours, and there's no way in hell I'm going to create separate news items for all of them. :) But they are worth mentioning, especially if you're looking for a new home in the wake of QBasic News's shutdown yesterday. So here you go:

The Basic Network (http://www.basicnetwork.net)
Nekrophidius and Rhiannon resurrected The Basic Network within minutes of when Wildcard shut down QBasic News, and this forum has quickly become the most active QB/FB forum on the 'net. There are already over 500 posts and 34 NEW members who have registered in the last 24 hours. This is the closest thing to the old QB News forums that's going right now.
Bad-Logic (http://ratatoskr.dragonhill.cc/forum/)
Marzec started this forum a while ago, but until yesterday it was just a back-up version of the old Bad-Logic.com forum that was popular last year until the website went down. Therefore, it is starting out with a rich archive of past posts and started with 42 users. Now it has 43 though, heheh. :) It's been fairly active in the past day.
QBasic Network (http://www.qbasicnetwork.com/)
Anarky actually started this website a few weeks ago, but it's been little more than a forum since then. (It also has a bit of Legend of Aquarius info -- about an RPG in the works). But otherwise it's a new QB forum that has has a tiny bit of activity and an annoying default skin (Blue Steel). Hopefully this site will expand become more active soon.
FreeBasic.net Forums (http://www.freebasic.net/forum/)
V1ctor, oh great one, god among men, the holiest of holy and creator of FreeBasic started this forum in response to the QB News FreeBasic forums shutting down. I guess you could say it's the spiritual successor of the QBN FB forums...but it's not nearly as active yet.
FBTK.net (http://www.fbtk.net/)
Okay, so FBTK.net really isn't new (it's just FreeBasic.tk with a new address and a new server) -- but it did move yesterday, the same day as all hell broke loose. So update your freakin links!
FBForum (http://www.fbforum.tk/)
VonGodric made this PHPBB forum in the exact same style as the old QBasic News forums -- it has the Smart Dark skin and the exact same forum headings. As of right now, though, it has very few members and is not really been active (maybe because it just started less than an hour ago, heheh).

I suggest that everyone congregate at a single QB forum and try to repopulate the old QB News crowd elsewhere, rather than spreading ourselves thin on lots of different forums. For now, The Basic Network is the most active one, so I'm going to throw my support behind them as the new QBN home.

Lachie Dazdarian begins QBasic games archive

Lachie Dazdarian, a HUGE QB gaming fan, began an enormous effort recently to collect all the good (or decent) QB games ever made into one gigantic searchable archive -- and he's made a lot of progress so far. A few weeks ago, he posted a preview version of the future site on the QBasic News forums and it was exciting and inspiring to see all of those great QB games collected together, rated and described. Somewhere on the web you can still access this preview version, but I don't know where to find it now that the QBasic News forums have shut down. The original post used to be at: this address. Maybe in the next issue I can give you more info.

QB45.com and V Planet! coming back within a week!

I have read in numerous places that the people in charge of QB45.com and V Planet! will be returning within the next few days. Fling-master and Jofers have posted about this at the QB45.com board, and Joe King (who is helming the V Planet! return) has also said that VP will come back by the end of the month. Now I know that these announcements have been made many times in the past and not come true, but once again I'll hold on to hope that it will actually happen this time. And if it does: HOORAY!!

FreeBasic Wiki Started!

V1ctor has started a FB Wiki, which is already become a great information source. I encourage everyone to contribute! http://www.freebasic.net/wiki/wikka.php?wakka=FBWiki

Project News

Dark Prevail unleashes an ArKade game

Dark Prevail recently released an arcade shooter game with old school wireframe graphics and a frenetic pace. It's also got a very simple name: ArKade. It's worth a download just to see the menu screen (it's actually really cool). The game's not bad either. :) Download it here (987KB).

Space Impakto makes an impact

Relsoft released a demo of an awesome space shooter on May 9th that apparently goes by the name Space Impakto. Like all of Rel's releases, this is very graphically impressive. Colorful, detailed enemy and gunfire sprites dart around the screen (complete with Mode7 2D effects) on top of nice backgrounds -- and even though it's at just 320*240 resolution, it still really impresses.

At this stage in development, it's really still just an engine demo -- and there's no real way to win (you just play until you run out of health). Rel posted this early release in order to get feedback and FPS reports from the Qmunity -- not that it's really necessary. The latest version runs at a full 60fps on a Pentium 233. That's pretty darn good. Download it here.

Mazerun by loking1235

Loking1235 released a cool FB minigame a few weeks ago where you guide your mouse cursor through mazes. It's called Mazerun. Here's his description: "Mazerun Can you make it through the maze? Use your mouse to move the little green ball to the red goal. Do not touch the walls or you will have to start over again. " Simple but addictive. You can get it at this website.

Z!re Gets Bored

If you're looking for a simple game, Z!re's BORED v1 is as simple as they come. Basically, don't let your mouse cursor hit the wall -- that's all there is to it. This game is a fun distraction for a few minutes... you can find out more at this address.

GFXLib Gets Alpha Capabilities

Angelo Mottola's FB graphics library that allows you to use the old QB graphics commands (and much, much more) got another new feature on May 13th -- Alpha channels in your PUT sprites. For more info, check out lillo's thread: here.

FBIde v0.4 Released!

VonGodric's much-heralded FreeBasic IDE had a new version released on May 18th -- you can read his news posts here and here, among other places. Version 0.4 features tabbed coding windows, quick run, code highlighting and a whole lot more. If you'd like to see a screenshot, there's one HERE. :) But you should really visit FBIde.sourceforge.net for the full scoop and to get a copy of this supremely useful FB coding tool.

FreeTile Library for FreeBasic

Xerol announced his plans to open up a FreeTile Library for FreeBasic where users will be able to share sprites for use in game projects through a database-driven website. I think it's a great idea. Here's some more info from Xerol:

Ok, while slaving over a 32x32 badly made grass tile in Paint last night, I really wanted to find a place where there'd be a bunch of tiles just ready to use.

The concept is that all these tiles would be free to use, in any project, commercial or not, as long as they were used with a FreeBasic game. (Or non-game program that for some reason uses sprites.) I'll provide the hosting myself unless the size gets out of hand.

Check out this thread to get involved.

MariuZ announces an RPG ... a Pure QB RPG!

There aren't too many of these getting announced anymore and they used to be a dime a dozen...pure QB RPGs. But they're not a completely extinct species. MariuZ just announced one at Jocke The Beast's board. The game will be written in pure QB except for sound, will have "selfmade music" and "hopefully about 5 hours of gameplay". You can see a screenshot here. I wish MariuZ luck!

Zero Divide releases new QB GUI

Zero_Divide released CycloNe v1.5 recently, a GUI library for QB 4.5. It has a nice Windows 95 look to it and is one of the better QB GUIs I've seen. You can find out about it at Zero_Divide's Site. Here's a list of features:

Work with high resolutions from 320?200 to 1280?1024 in 256 color palette
Loading of BMP pictures in deph 8 bit
Support XMS Memory
Whole Support of mouse
All elements have its own features and can be changed as well
Built using SVGAQB v2.6

Other News

Dark Ages II: Engel gets new demo release (!)

As many of you may recall, back in 1998, Michael Hoopman's Dark Ages I: The Continents was the talk of the town. It was one of the first finished QB RPGs, and it got a lot of recognition (it was even included on the pack-in CD of a mass market PC gaming magazine - PC Gamer or PC World or one of those mags). So when Hoopman started making a sequel to Dark Ages, it was big news. QBasic: The Magazine (the reigning QB zine of the time) spent quite a bit of time hyping it up, including a huge preview in December 1998 and constant updates. DA2 got quite the fan following in the QB scene.

But that was 1998. Now it's 2005. I'm sure most people assumed that Dark Ages II was just another dead project, abandoned somewhere in mid-development and never to see the light of day. Well, it turns out that DA2 never ended up dying like we all assumed. It ended up being ported to Visual Basic and is actually STILL in development.

On May 15th, Michael Hoopman released a new beta release of the game at his website, Dark Knight Software. As a huge fan of the first game, I was amazed when I heard this news and rushed to check out ... what ended up being a fairly lackluster demo that hasn't changed much from its QB demos back in 1999. And it still features the same old sprite graphics that look incredibly dated these days. Oh well. Maybe one day when it gets finished it will manage to live up to the simple fun of the first one.

New QBXL Audio Edition

SJ Zero has *finally* released a new QBXL audio version after more than a year. Like the previous three audio editions, this features satire and parody news with a Daily Show-like radio delivery style. This latest issue made fun of several things around the Qmunity, and even mentioned myself and QB Express in its report on Adigun A. Polack's FreeBasic Demo Competition. You can find the new edition here: qbxl.net/downloads/qbxlAudio4.ogg

QBasic GUI Development

Written by Jacob Palm

Intro

Have you ever been annoyed by Windows taking up way to much RAM and CPU power, and felt like switching to DOS, but then haven't because of the lack of a graphical interface? I know I have. That's why I decided to make a graphical interface (GUI for short) myself. When you make a GUI yourself, you can leave out all the stuff you newer use anyway, which will make the GUI faster and smaller, allowing it to run on old computers, too.

Of course you don't necessarily have to replace Windows or DOS with your GUI. You can make one just for fun, or maybe for other people to use. The reason I make a GUI is that I think it's funny to see how much I can get the computer to do, how nice I can make it look, how far I can push QBasic and such. I've also really learned a lot about computers while making a GUI. But whatever reason you may have to make a GUI, I'll do my best to tell you something about QBasic GUI's. Don't expect to find any code here, this article is purely theoretical. I'll write some stuff about what a good GUI should have, and give some tips. Maybe I'll write a tutorial for the next issue of QB Express.

Excuse me if my english isn't perfect, don't forget that I'm only 15 years old and from Denmark. This is the first article I've ever written. I hope you'll find it interesting.

What a good GUI should have

What your GUI should contain of accessories is fully up to you. But there is some accessories the user would expect to find in a GUI. Below I've made a list of some accessories every GUI should have.

Nice controls with reasonable colors
The most important thing in a GUI is (in my opinion) the design of the interface. Let's say for example that somebody wrote a simple amazing GUI, which could do just about anything, but used bright green text on yellow windows, and had buttons with random shapes. Nobody would want to use a GUI like that (Okay, maybe that was a somewhat extreme example, but I think you got the point).
A program launcher
A desktop, program manager, filemanager or something like that, which launches programs (both internal and external). I know you may think this sounds stupid. I mean, all GUI's have a program launcher, right? Well, no. I've actually seen a lot of GUI's which didn't have the ability to run standard DOS programs. Users don't like when they have to quit the GUI to run a program, and then start the GUI again. Many users would ditch a GUI without a glimpse if it couldn't run standard DOS programs.
A filemanager
If the GUI doesn't use a filemanager as the program launcher, then a filemanager should be included. Users like it when they don't have to quit the GUI to perform file operations. Many people also find it easier to perform file operations using the mouse.
Mouse support
Mouse support is not really necessary, but it's a big plus if a GUI has it. It should however be able to function without mouse (if the user's mouse is broken or not connected correctly or something like that)
A file viewer/editor
Let's just face it. MS-DOS Edit is a good text editor, but it doesn't belong in a GUI, since it runs in pure text mode. It's okay if your GUI uses MS-DOS Edit to edit files, but it'll look better if you make a graphical text editor. This has proven to be a hard task, though, and therefore many GUI's just use MS-DOS Edit (including mine, for now)
Entertainment
The user has been working in your GUI for hours, and needs a brake. What would be better than some kind of entertainment included with the GUI? It doesn't have to be a big 3D shooter, just a small game like Tic Tac Toe or reversi. The game should have some AI, so that the user can play against the computer if he/she doesn't have anybody to play with.
Settings and customization Users like it when they can change the colors of the GUI, add a background image, modify icons and change settings. Some just use the standard settings, but most users like to personalize the GUI. Customizable icons is definitely a plus, users don't like having to type the path and filename of a program each time they want to run it.
Documentation and a proper error handler
Many GUI's just exit without a warning if an error occurs, while others give an error code. Unless the user is a QBasic programmer, he/she won't know what the error code means. Therefore, I recommend that you make a proper error handler, which will tell the user what went wrong, and how the problem can be solved. It's always a good idea to include some documentation with your GUI for the user to look in if he/she can't figure out how to do something.

Of course there's more than what I've listed here. This is just a list of some of the most common things users expect to find in a GUI. You could of course release a SDK (Software Development Kit) for your GUI, allowing users to write their own accessories which fit in to the GUI nicely. Some users actually send their creations to the author of the GUI, which in some cases include it in the GUI, making it even better.

Tips

I've listed some tips below which you may find useful in the development of a GUI.

Many people like it when the GUI displays some icons. If your GUI is made up of text and windows only, it might be a little boring to look at. But don't just make some icons, they should fit in to the correct places. For example, an icon of a cow doesn't belong in an error-message (unless it's a dead cow, maybe)
Split up your GUI in several EXE's. This will help improve the stability of the GUI. For improved stability, each accessory should be in it's own EXE file. Then, when an accessory makes an error and exits, the user will still return to the program launcher. Splitting up the GUI in several EXE files will, however, make it a lot harder to do multitasking(thank you to Todd Suess for this tip)
Use screen modes with page-support. It will drastically reduce flicker in your GUI if you draw the screen on a videopage before you show it on the screen. The best screen mode for GUI's (which support pages) would be screen 9, since it has a high resolution (640x350 pixels). You can also use the statement "WAIT &H3DA, 8" (without the quotes) to wait for the next screen redraw before drawing something. Don't use it in a loop, though, that would drastically reduce the speed of the GUI.
Use a font routine which doesn't display capital letters only. IT'S VERY ANNOYING TO READ TEXT WITH UPPERCASE LETTERS ONLY, as you may see.
If possible, provide an e-mail address or website where the user can get support if he/she has a problem or question regarding the GUI.
Try to make the interface as easy to use as possible. It's not easy using a program if the buttons only have pictures on them which doesn't tell what the button does. The best way would be to add text to the button, or a tooltip.

There are more ways to optimize your GUI, but most of them isn't GUI related, but works in all QBasic programs (some of the tips above work in all QBasic programs, but they're very useful in GUI's, so I decided to list them anyway)

Links to GUI pages

There are some QBasic GUI related pages out there, but not that many. I've listed below some of my favorite sites (and my own, of course).

Sepent Basic GUI & OS Home
Has a lot of review of QBasic GUI's. It isn't updated very often, though.
Data Components - GUI Reviews
A very large GUI Review site by Todd Suess. Has more than 50 reviews.
JacobPalm.dk
My own GUI site. Has a lot of reviews, some tutorials and a forum.
East-Power-Soft
It's in german, but if you speak german it's a great page with a lot of reviews.

There used to be more GUI sites, but most of them are closed now.

That's it for now

Well, I don't have much more for you this time. I hope you enjoyed reading this article, and found the contents useful. If you have any questions or comments regarding this article, feel free to e-mail me at hvalrossen@jacobpalm.dk. You can also post in the forum at my website. Good luck with your GUI programming!

Jacob Palm
(The Walrus at some forums)

Make sure you visit JacobPalm.dk, Jacob's great QB GUI site and last month's QB Express Site of the Month!

I.F. Games Chapter 5:
"Teaching English to our computer"

Written by Na_th_an

Y'ello, guys and girls. One more month and one more chapter in which will become a true Quixote. Originally I had planed just 3 chapters, but you see. Things are gotten out of hand, mainly 'cause I've found that some things really HAVE TO be explained in depth. If I had just thrown in a bunch of code in the last chapter, covering the whole engine, you would have ended with an IF engine which would be worth nothing, tutorial-wise. I have two main objectives with this series, the first of them being you learning to write proper text adventure games for yourself, and the second, underlying one which is teaching people to produce better code. That's why this series will take much longer than expected, I just want to discuss every bit, how it works and why is it coded that way, 'cause the goal is that you are able to write your own engine instead of having to use mine.

This chapter we're discussing about the parser module. First of all we'll make a quick reminder on what we want this module to do and then we'll see how.

Coding the Parser Module

Our parser module will be comprised of two, clearly differentiated parts. As they both use the same subroutines for string slicing and formatting, we've decided to place them both together in the parser module 'cause they both, in different ways, parse stuff: these two parts are the scripts interpreter and the player's command interpreter. Before diving into these parts, let's examine and explain the auxiliary subroutines we are gonna use. These subroutines will be kept internal, i.e. they won't be referenced in the .bi file as we won't need them outside (read the previous chapter to refresh your mind about this topic).

All the snippets in this chapter should go inside a file called "parser.bas", for example. The exported SUBs/FUNCTIONs will be in "parser.bi".

Auxiliary functions

If we need to parse a string containing several words (which can be a natural language sentence, or a line of code - think in tokens and values as words), the first thing we need is a subroutine which slices the string into words and return them conveniently formatted. If we are gonna try to understand what's in the sentence, we need to easen the things a bit to the computer: we need trimmed words (with no whitespace) in lowercase. This is what the next piece of code does: it takes a sentence, slices it, and stores each word in an array index.

We will set this array (the one which will contain each word in the sentence) as a shared variable so it is accessible from any subroutine or function in this module. The string containing the whole sentence will be a shared variable as well, which should be able to be modified or read from the outside, so we'll create a SUB and a FUNCTION to do such tasks which will be exported in the .bi:

Const phraseLENGTH = 50

Dim Shared words(phraseLENGTH) As String
Dim Shared phrase As String

Sub Parser.setPhrase (newphrase As String)
   phrase = newphrase
End Sub

Function Parser.getPhrase ()
   Parser.getPhrase = phrase
End Function

I think that 50 words is far enough. In fact, I doubt that you will need more than 10.

The slicing function will read the string character by character, stopping when finding a space and storing what he got so far as an array element. It will do a couple things more: it will take track of multi-proposition sentences (such as "get book and read it", or "get pen, open the case and put the pen inside it"), and will split the sentence accordingly.

This can be done in a relatively easy and simple way: we will only parse the sentence until we find a separator (such as a comma, a stop or the "and" word), then we'll wipe out what we have parsed, so the next time we call the subroutine the next portion of the phrase will be parsed. For example, imagine that phrase contains "get pen, open the case and put the pen inside it":

1.- The first time we call to the function, we get:

words(0) = "get", words(1) = "pen", words(2-50) = ""
phrase = "open the case and put the pen inside it"

2.- Next time:

words(0) = "open", words(1) = "the", words(2) = "case", words(3-50) = ""
phrase = "put the pen inside it"

3.- And the next one:

words(0) = "put", words(2) = "the", words(2) = "pen", words(3) = "inside", words(4) = "it", words(5-50) = ""
phrase = ""

You'll see how it works later with a simple (coding) example. The code is as follows:

Sub Parser.Parse
    Dim word As Integer
    Dim i As Integer
    Dim m As String

    ' To make things easier, we make a first pass changing every separator
    ' for a common symbol, which happens to be "&":

    For i = 1 To Len (phrase)

        If i < Len (phrase) - 1 Then
            If Mid$ (phrase, i, 3) = "and" Then
                If i = 1 Then
                    phrase = "&" + Right$ (phrase, Len (phrase) - i - 2)
                ElseIf i < Len (phrase) - 2 Then
                    phrase = Left (phrase, i - 1) + "&" + Right$ (phrase, Len (phrase) - i - 2)
                Else
                    phrase = Left (phrase, i - 1) + "&"
                End If
            End If
        End If

        m = Mid$ (phrase, i, 1)

        If m = "." Or m = "," Then
            phrase = Left$ (phrase, i - 1) + "&" + Right$ (phrase, Len (phrase) - i)
        End If

    Next i

    ' Okay, after some string slicing now we have all the separators replaced by "&".
    ' Sometimes I wish BASIC had the regular expression managing Perl has :P

    ' Now break up the phrase into words. Stop at & and return the remaining.
    ' This will allow to use . and , to tell the Parser.Parser several actions
    ' from within the same command, as explained.

    word = 0: words(word) = ""         ' word will keep track of the array index

    For i = 1 To Len (phrase)          ' loop for every char in the string

        m = Mid$ (phrase, i, 1)        ' get it

        If m = " " Then                            ' Whitespace found
            If words (word) <> "" Then             ' If current word is not empty
                word = word + 1                    ' Go to next word.

                If word = PHRASELENGTH + 1 then    ' If no space left in the array
                    phrase = ""                    ' clear phrase.
                    Exit For                       ' exit.
                End If

                Words (Word) = ""                  ' Initialize next word
            End If

        ElseIf m = "&" Then                        ' Separator found
            If i < Len (phrase) Then               ' Trim if more chars in phrase:
                phrase = Ltrim$ (Rtrim$ (Right$ (phrase, Len (phrase) - i) ) )
            Else
                phrase = ""
            End If

            Exit For                               ' Let's get outta here.

         Else
            words (word) = words(word) + lcase$(m) ' Any other char gets added to the
                                                   ' current word.
        End If

    Next i

End Sub

You can see this in action with the following testing code:

Dim o As String

Do
   Input o
   Parser.setPhrase o

   Do
      Print Parser.getPhrase
      Parser.parse
   Loop Until Parser.getPhrase = ""
Loop

It's important that you fully understand how this sub works. This a fairly good example of string slicing works, complete with substring replacement. It's also important that you understand how to make it work: First you must feed the sentence to the engine using Parser.setPhrase, then you call to Parser.parse until getPhrase returns the empty string. When we put together the main loop, we'll have to run the common actions and the post-input exceptions until getPhrase returns the empty string. The diagram we saw two chapters ago ends having this shape:

' Main loop in pseudo-code

DO
   
   
   

   DO
      
      
      DO
         parse phrase.
         interpret phrase.
         [
         |
         |]
      LOOP UNTIL phrase is empty
   LOOP UNTIL 
LOOP

Once we've seen the auxiliary functions we're ready to go ahead to the important things, for example the interpreter. But before...

We need a dictionary!

The dictionary in our game will serve two purposes. The most important and basic is to be able to identify which kind each word is, i.e. it is a verb, a noun or and adjective. The second one, not less important, is to be able to have synonyms. Check Chapter #1 again for a deeper discussion about the meaning of this all.

We start, as always, defining data types, constants and module-level shared arrays.

CONST MAXWORDS = 1000         ' Max. number of words in the dictionary.

CONST WTVERB = 1              ' Word types
CONST WTNAME = 2
CONST WTADJ = 3

Type DictionaryType
     id as Integer              ' Word ID (useful for synonyms)
     w as String * 20           ' Word.
     typ as integer             ' Word type (1 = verb, 2 = noun, 3 = adjective).
End Type

Dim Shared D (MAXWORDS) As DictionaryType

As with the location descriptions, we'll store the dictionary in a separate text file with an easy to parse format. We just need id, the word itself, and a numeric type. The easiest way of doing this is having a word per line with those data separated by commas, i.e.

1,n,1
1,north,1
2,s,1
2,south,1
3,e,1
3,east,1
4,w,1
4,west,1
5,ex,1
5,examine,1
5,look,1
100,book,2
101,jewel,2
200,red,3
201,green,3
202,big,3
203,empty,3
9000,it,2
9000,them,2

(remember that you should include "it" and "them" as synonyms and names).

With the data stored in such an easy format, loading it into the D array is really simple, we just create an idex variable as iterator and fill the D array until we reach MAXWORDS or the end of file. This function will be exported in the .bi file:

Sub Parser.Load (fileName As String)
    Dim f As Integer
    Dim wrdIdx As Integer

    ' Just load the dictionary from the file.

    f = freeFile

    Open fileName for Input as #f

    wrdIdx = 0

    While (Not(Eof(f))) And (wrdIdx <= MAXWORDS)
        input #f, D (wrdIdx).id
        input #f, D (wrdIdx).w
        input #f, D (wrdIdx).typ

        wrdIdx = wrdIdx + 1
    Wend

    Close #f

End Sub

Coding the interpreter

The interpreter is the heart of the first part of the Parser. It is in charge of translating from English to the language the engine understands, which is a very "simple simplification" of English with just one verb per sentence, and whether one or two nouns each one with an optional adjective, provided they are in the dictionary (check back chapter #1 for a more complete explanation). Every other word is wiped out. At a later time, the common actions and the exception manager will rely in these "important words" extracted from the player input. So the first thing we need is adding a few module-level shared variables:

Dim Shared Verb As String, Noun1 As String, Noun2 As String, Adj1 As String, Adj2 As String
Dim Shared PrevNoun As String, PrevAdj As String

This function is also in charge of doing some dirty hacks needed for the English language and its phrasal verbs. Note that we have to find the "verb" 'cause we are gonna use it as a "command" for our engine. In other languages, you have a word for each verb. In English you have very different meanings depending on the preposition which comes with the verb, i.e. "look for" and "look after" have completely different meanings (in Spanish we have different words: "buscar" and "cuidar", i.e. interpreting is easier), so to decide which action the engine should perform we can't only focus on the verb. As prepositions may come in different positions inside the sentence (you can write "put the shirt on" or "put on the shirt") we have to "fix" it, or, better expressed: we can't just extract the verb from the words array, we have to figure it out. Basicly, if we find a phrasal verb we scan the rest of the words for prepositions, then we change the verb accordingly. For example, if we find "turn", we scan the rest of the words. If we find "on" in the sentence, we change the verb for "turnon"; if we find "off", we change the verb for "turnoff". That way, a sentence which is "turn the lamp on" will become "verb: turnon, noun1: lamp".

We need a simple function that finds a word in the array "words" starting from a given position:

Function Parser.findFrom (from As Integer, w As String) As Integer
    Dim res As Integer
    Dim i As Integer

    res = 0

    For i = from To PHRASELENGTH
        If words(i) = "" Then          ' We find an empty word: no more words
            Exit For                   ' in the sentence.
        End If

        If words(i) = w Then           ' We found it!
            res = -1                   ' Return true
            Exit For
        End If
    Next i

    Parser.Findfrom = res

End Function

This interpreter subroutine introduces the first finite state machine (FSM from now on) we are gonna use in this engine. Basicly, a FSM is just "something" that has a state and reacts to something external, changing its state for another one depending on what happened. FSMs are very used in parsing. In this scenario, that "something external" is the symbol being read, in this case a new word; imagine that we put each word in a transporting tape and we have a machine that gets them one by one, sequentially, and processes them. We'll define four states for our machine which will be "init", "found verb", "found noun1", and "phrase complete". In the following diagram there's an explanation on how this FSM works, according to the state it is in and the word read:

State 0: "init"
In this state we are searching for a verb, ignoring everything else.
If found a verb, assign it to the variable "verb" and jump to state 1.
State 1: "found verb"
In this state we are looking for a noun with an optional adjective. If the word found happens to be an adjective, we assign it to the variable "adj1" and we keep in this state. If the world found happens to be a noun, we assign it to the variable "noun1" and jump to state 2.
State 2: "found noun1"
In this state we are looking for an optional second noun (for constructions such as "put A in B"). This state works exactly as State 1, but jumping to state 3 when noun 2 is found.
State 3: "phrase complete"
We just kill the FSM here.

If we run out of words at any time, the FSM is killed as well.

There's some other important things that this Subroutine do:

This subroutine remembers the last entered noun so you can use "it" or "them" in your phrase. It will update "noun1"/"adj1" or "noun2"/"adj2" accordingly.
We also accept the use of synonyms. Many things can be named in different ways (this is a fundamental feature in Spanish, for example, if you want a playable engine), but we want just one way in our engine (we should have to replicate lots of code just for each synonym if we didn't have this facility, i.e. having to reply to "n" and "north" in the same way!). This sub will identify the player's input if it is in the dictionary but will remember the first synonym instead of the actual word entered. For example, if we have "child", "kid", and "lad" in the dictionary, in that order, and with the same 'id', if the player enters "give money to the kid" the interpreter will remember "verb = give, noun1 = money, noun2 = child". Now you can just react to "child" in your exceptions, every synonym will be changed to that only word.

This is the code. Pay special attention to how the FSM flows.

Sub Parser.Translate Static
    Dim state As Integer
    Dim i As Integer, j As Integer
    Dim word As Integer
    Dim assignA As String, assignN As String

    ' * Identifies the synonyms and word type (verb, noun, adjective)
    '   According to the dictionary file.
    ' * Whipes out unneeded words from the words() array, such as "the, as"...
    ' * Substitutes "it", "them"... etc by the remembered word.
    ' * Updates remembered word.

    ' Phrasal verbs force me to do some kinky hacks to get this working.
    ' I mean, some verbs change its meaning depending on the preposition
    ' used, and that preposition isn't always just after the verb, i.e.
    ' "turn the torch on".

    ' This SUB does the "dirty work" of simplifying simple English.
    ' Note that this is the most difficult SUB to adapt when translating
    ' an IF. In fact, you could only translate this one, as it is,
    ' in fact, some kind of "ENGLISH TO ENGINE" translator :P

    ' Phrase always follows the same structure:

    '  VERB [[ADJ1] NOUN1 [[ADJ2] NOUN2]],
    
    ' we have to wipe everything out but this.

    ' We can do this with a very easy FSM (Finite State Machine):

    state = 0           ' 0 = Init
                        ' 1 = Found Verb
                        ' 2 = Found Noun1
                        ' 3 = Phrase complete

    ' Let's analyze word by word.

    ' Don't forget the good ol' initialization:

    Verb = "": Adj1 = "": Noun1 = "": Adj2 = "": Noun2 = ""

    For i = 0 To PHRASELENGTH

	' Dirty optimization: As soon as we find an empty word, it
	' means that the phrase has finished, so we exit:

	If words (i) = "" Then Exit For
    
        ' Find words (i) in the dictionary. Linear search. We could make
	' this in a better way, for example sorting the dictionary alpha-
	' betically and using a binary search which is O(logN). Anyway,
	' O(N) is not that bad for this:

        word = -1
        
        For j = 0 TO MAXWORDS
            If D (j).w = words (i) Then      ' Found in the dictionary!
                word = j: Exit For
            End If
        Next j

        If word <> -1 Then                   ' If word was in the dictionary:

        ' Find 1st synonym:

            For j = 0 TO word                ' This snippet just selects
                If D(j).id = D(word).id Then ' the first word that's in the
                    word = j: Exit For       ' dictionary with the same id
                End If                       ' as the word the player entered
            Next j                           ' ie. the 1st synonym.

            ' Found, what type? (verb, noun, adjective?)
            
            Select Case D(word).typ

                Case WTVERB:                 ' Found a verb

                    If State = 0 Then        ' We only want a verb in state 0.
                        verb = D(word).w
                        State = 1

                        ' Here comes the hacks!
                        ' I can think of takeoff puton turnon and turnoff
                        ' Basicly we look for the preposition further in the phrase.

                        Select Case verb
                            case "take":
                                If Parser.findFrom (i + 1, "off") Then
                                    verb = "takeoff"
                                End If

                            case "put":
                                If Parser.findFrom (i + 1, "on")
                                    verb = "puton"
                                End If

                            case "turn":
                                If Parser.findFrom (i + 1, "on") Then
                                    verb = "turnon"
                                ElseIf Parser.FindFrom (i + 1, "off") Then
                                    verb = "turnoff"
                                End If

                        End Select
                        
                    End If

                Case WTADJ:                  ' found adjective

                    ' This way we can use more than 1 adjective per object, i.e.
                    ' "small green box" will result on adj1 = "smallgreen" and noun1 = "box",
                    ' as long as words are well defined in the dictionary.

                    If State = 1 Then Adj1 = Adj1 + D (word).w
                    If State = 2 Then Adj2 = Adj2 + D (word).w
                    
                Case WTNOUN:

                    ' ¿Pronoun? it/them... etc, just check "it" if we set up the synonyms correctly.
                    
                    If D(word).w = "it" Then
                        assignN = prevNoun
                        assignA = prevAdj
                    Else
                        assignN = D (word).w
                        assignA = ""
                    End If

                    ' Depending on the FSM state ...
                    
                    If state = 1 Then
                        noun1 = assignN
                        If assignA <> "" Then adj1 = assignA
                        state = 2
                    ElseIf state = 2 Then
                        noun2 = assignN
                        If assignA <> "" Then adj2 = assignA
                        state = 3
                    End If
            End Select

        End If
        
    Next i

    ' Remember for "it"/"them"/etc: Always remember noun1/adj1 unless noun2/adj2 exists and
    ' was previously used:

    If noun2 = "" Then
        prevNoun = noun1
        prevAdj = adj1
    Else
        If prevNoun <> noun2 Then
            prevNoun = noun1
            prevAdj = adj1
        else
            prevNoun = noun2           ' This is redundant and not needed,
            prevAdj = adj2             ' but here for readability.
        End If
    End If

    ' This way, this (which makes sense) can be entered:
    ' > get box
    ' > open it
    ' > put pencil into it
    ' > close it

End Sub ' PHEW!!

We just need a way to retrieve the verb, nouns and adjectives from outside.

Function Parser.getVerb ()
    Parser.getVerb = verb
End Function

Function Parser.getNoun1 ()
    Parser.getNoun1 = noun1
End Function

Function Parser.getNoun2 ()
    Parser.getNoun2 = noun2
End Function

Function Parser.getAdj1 ()
    Parser.getAdj1 = adj1
End Function

Function Parser.getAdj2 ()
    Parser.getAdj2 = adj2
End Function

How the player command interpreter works

We have seen a tad of subroutines and you may feel a little puzzled. Before we start with the scripts interpreter, I think we should stop a bit on explaining how does this all work.

Let's define what we want to do: we want to read what the player has entered, and extract the important information from there so we know what to do. The command interpreter just reads the player's input and guesses what he or she wants to do. We need a simple but descriptive way to pass this information to the Objects Manager. Just five words (maximum): "verb adj1 noun1 adj2 noun2" are enough. So the command interpreter translates the player input (in natural language) to these 5 words. And this is done in several steps:

0.- Initialize: We just call "Parser.setPhrase" passing a string with the player's input. The local variable "Phrase" stores it. This input may contain more than one sentence, delimited using separators.

1.- Slice the string: The subroutine Parser.parse takes the string containing the player's input (stored in the variable Phrase), and breaks it into words, which are stored in the local array "words ()". If Phrase contains more than one sentence (delimited with separators such as "and"s, commas or stops), the subroutine just considers the first sentence (from the beginning to the first separator); then it "consumes" this sentence from the string (leaving the rest right after the first separator). At any time, we can read the "Phrase" from outside this module calling to the function "Parser.getPhrase".

2.- Translate words (): The subroutine Parser.translate reads the words and extracts the info from them: verb, adj1, noun1, adj2 and noun2. For this subroutine to perform this action correctly, a correct dictionary file has to be present on memory. Note that this file should contain every word you want the engine to understand. Ever word found in the array words not found in the dictionary won't be taken in account.

3.- At this point we would call the Object Manager's functions and/or run scripts with exceptions, just to execute the player's will examining these five words produced by Parser.translate. This will be covered on future chapters.

4.- If Phrase is not empty yet, go back to 1 to process the next sentence.

Tips for creating a dictionary

You don't need all the English language in your dictionary array, just the verbs you are gonna obey to (which most of the time are just north, south, east, west, ..., examine, get, take, drop, put, wear ... etcetera), and all the nouns and adjectives used to identify all the objects (common and fixed) and non playing characters in your game.

Every word has an ID. synonyms have the same ID. This ID is an integer, so it can climb to 32767 in QB or way more than 2 billion in fB. To keep things tidy, I begin assigning numbers from 1 onwards for verbs, for 1000 onwards for nouns and for 2000 onwards for adjectives. Special stuff at the end, i.e. the prepositions, which I give a 9000. This is not done "just because". Note that verbs are the most used words in the game, then nouns, then adjectives. As we search the array linearly, it's good practice to order the stuff from "most used" to "less used". A good improvement to the engine would be to have the dictionary alphabetically sorted and use a binary search, but I'll leave that as an excercise for the coder.

Let's begin with our dictionary. We'll start with the directional commands:

1,n,1
1,north,1
2,s,1
2,south,1
3,e,1
3,east,1
4,w,1
4,west,1
5,ne,1
5,northeast,1
6,se,1
6,southeast,1
7,nw,1
7,northwest,1
8,sw,1
8,southwest,1
9,up,1
10,down,1
11,enter,1
12,exit,1

Note the use of synonyms: "se" and "southeast" are synonyms so they use the same ID. Note how this works: if the player enters "southeast" as a comment, the translator will find it in the dictionary, and then find the first synonym (first word found in the array with the same ID): "se", so "verb = se". That way we just have to code the engine to obey "se", not both "se" and "southwest". I tend to do this, i.e. have the shortest form of each word as the first synonym. That way I have to type less when coding the engine :P It is also faster, as less characters have to be compared. Other people think that it is more intuitive to have the most expanded word as the first synonym, just for readability, as they prefer to read:

If verb = "north" Or verb = "south" Or verb = "east" Or verb = "west" Or ... Then movePlayer
If verb = "examine" Then doExamine
...

rather than

If verb = "n" Or verb = "s" Or verb = "e" Or verb = "w" Or ... Then movePlayer
If verb = "ex" Then doExamine
...

Just decide what's your favourite approach. You know what's mine :P <- lazy coder.

Back to the dictionary. Now we're gonna add the verbs corresponding with the actions we are gonna allow in this game plus their synonyms:

13,i,1
13,inventory,1
13,objects,1
14,ex,1
14,examine,1
15,look,1
15,description,1
16,x,1
16,xx,1
16,exits,1
17,get,1
18,drop,1
18,leave,1
19,put,1
20,take,1
21,puton,1
21,wear,1
22,takeoff
22,unwear,1
23,turn,1
...

Note the synonyms again: "inventory" or "objects" will be changed for "i". "examine" for "ex". In the same way you can use "put trousers on" which will get extracted to "verb = puton, noun1 = trousers". If the player wants to ask for the exits, he can whether write "exits", "xx" or "x", which will be translated to "x". In our engine (the objects manager and the exceptions scripts), we'll have to respond to those first synonyms, i.e. "i", "ex", "n", "x", etcetera. Again, if you prefer having this the way around and enjoying of a more readable piece of code, go ahead. I prefer this way: less typing, faster engine.

Take special attention to this paragraph, 'cause this is a side effect of the hack we use for phrasal verbs: all those phrasal verbs HAVE TO be in the dictionary, but not the prepositions that come with them. For example, if we allow "turn off" in our game, "turn" should be in the dictionary, but not the word "for" (after all, FOR is a preposition which we DON'T NEED). Note how it works: 1.- The translator finds "look", 2.- if we have defined it as a phrasal verb (take a glance at the code - you have to manually add each phrasal verb in the 'here comes the hacks' section) it searches the rest of the words for a preposition. 3.- If it finds "for" (again, blatantly hard-coded, check code), it changes the verb from "look" to "lookfor". So adding "for" to the Dictionary is whether futile (if you add it as a verb it will be ignored once we exit "state 0" in the FSM) or error-prone (if you add it as a name or adjective really nice odd stuff could happen). Plus the more words in the dictionary, the slow the engine will be - just avoid adding words that are not going to be used ;)

There are more restrictions with phrasal verbs and their synonyms. I'll try to show you this with an example. Let's consider the construction "put shirt on". To make it work, "shirt" (noun) and "put" (verb) have to be in the dictionary. The translator will replace then "put" for "puton" when it finds "on" further in the words array. Okay, that worked great, in our objects manager we'll do the correct actions reacting to verb = "puton". But what if the player prefers to use "wear shirt"? It's clear that we have to define "wear" as a synonym of something. "put" is in the dictionary, why not use it? No way, our engine will only react to "puton", so puton must be in the dictionary as well, and "wear" should be synonym of "puton". Note that you can't do this the way around (i.e. "wear" as 1st synonym and "puton" as synonym of "wear"), 'cause once the engine substitutes put for puton (after finding that "on" is in the words array) it won't look for synonyms. So for actions that can be expressed with a phrasal verb, make sure that this phrasal verb plus the preposition is the first synonym, then add the remaining, then add the phrasal verb without preposition with a different ID. With "puton" we have "puton", then "wear" with the same ID, then "put" with a different ID. After all, "put" alone is also used (to "put" something inside a container), so it is in the dictionary anyway.

Once you've finished adding verbs, let's begin adding nouns. Note that if you begin to ID the nouns from 1,000 onwards, you'll be able to add more verbs at a later time. Begin entering the objects first, then the fixed objects. Same with adjectives. You should add every noun and every adjective that you think the player could think on entering. Note that the better response your IF has, the greater it is. IF players love to be responded to almost everything they might enter. That's why betatesting is so important when coding an IF. Let your friends play to it and note all the things they write that don't get a proper reply, just to add them later! :D

-oOo-

I was gonna explain the scripts interpreter for the exceptions now, but I've just noticed that this article is really long and I don't want to take half the e-zine for (it can take as much as this!) me so... See ya in the next chapter!

If you missed them, check out part #1, part #2, part #3 or part #4!
You can contact Na_th_an at this link.

THE ART OF DATA VALIDATION

Written by Stéphane Richard (Mystikshadows)

INTRODUCTION:

When you think of data validation, what's the first thing that comes to your mind? Is it, by any chance, to enter numbers when an application is expecting numbers out of you, the user? If so, then you're already well under way to grasping the full understand of just what data validation is all about. In essence data validation is about having valid data for a given type of variable and wether you are creating a business application or a game, good data validation will add a certain level of professionalism to your programming endeavours. There's more to data validation that simply validating the data, alot more as you'll see there is alot of things that can be done to help in the data validation process.

In this document, we will cover all you'll ever need to know about data validation, what it really means, how to use it effectively and ultimately how to minimize the use of data validation while still assuring that the data is indeed valid. So get ready, the journey begins here.

DATA VALIDATION DEFINITIONS AND CONCEPTS:

Data validation, as explained above, is making sure that all data (whether user input variables, read from file or read from a database) are valid for their intended data types and stay valid throughout the application that is driving this data. What this means is data validation, in order to be as successful as it can be, must be implemented at all parts that get the data, processes it and saves or prints the results. Let's take the time and list those parts here and explain why they should be considered.

User Interactivity Screens And Forms:
Any part of an application that requires the user to enter the data (in a data entry screen for example) should most definitaly be considered as a prime candidate for data validation. Human error always end up as the prime suspect for invalid data no matter how well intended the users are. You'll find that statistically, a very big majority of the invalid data situations are usually caused by human error.

File Manipulation Routines:
This entails all file related operations such reading from the file or writing to the file. Because usually, the data saved is the result of user supplied information, it is good practice to install a data validation procedure at this level. This includes database driven applications or even just a game screen for the settings to the game for example. when reading a file, double checking what you are reading is also good practice if not for anything else, to validate that the datafile is valid and not corrupted in any way.

Import and Export Routines:
Indeed, when you plan to have your application able to save the same data in different file formats for different other applications, you need to make sure that the other applications will be able to open the file, as expected, without a problem. The reason I distinguish Import and Export from regular File Manipulation is because they are, in most cases independant of one another. These reasons as especially true when the import/export is to/from another database system. And let's face it, today, Import and Export are a very sought after feature.

These are the 3 major areas where you'd want to be sure that proper data validation is applied properly. This will only help with the rest of the application because you'll be able to cross out the data as being a cause for problem in possible errors that might slip into the application. That is, of course, once the data validation is debugged. But making sure that these are implemented in the development process rather than after the program is done will help minimize the burdon of integrating data validation in your application. Let's take a look and the types of validation that exist and are commonly used to give you an idea of where they can be used as well as how.

THE MANY TYPES OF DATA VALIDATION:

Why different types of data validation? The answer is simple. Essentially everything depends on the reason why you'd want to do data validation, it's degree of importance (as far as the data available to the application) and the actually type of the data as well. Here's a quick example just to put you into focus. Let's say you're making a mortage calculation program (that will be used by professionals all over the the continent). Typically, this kind of application would get initial data for the calculation of the mortgage itself. Hence a Principle amount, a length of the load, an interest rate, a data of first payment, the number of compounding periods per per year. This would be aside the client's information itself such as address, telephone number and the likes. Once the loan related data is entered the software would offer to generate an amortization table for each payment stating the payment amount, the amount give to the payment of the interest, the amount given towards the payment of the capital itself and some running totals at each payment period. If the initial data ends up being wrong, can you imagine just how bad the amortization table would end up being at the end of the calculation? Don't you think that the entry screen should be 100% sure of it's data before it goes ahead and performs the generation of the amortization table? The answer to this question ultimately must be yes. For the sake of the customer and the financial institution that will be loaning the money. With this in mind, let's see here what we can do to help the software make sure that the data is valid all the way.

We will be using the example of a mortgage calculation application because this, and other directly or indirectly related types of application such ass long term rental places, banks, realestate related businesses will love the fact that the data must be accurate for the reasons mentionned above and aq couple more that we'll see later in this document. So let's get right to it. The first thing will see is the different types of data validation that can be performed and describing them.

Field Level Validation:
The typical scenario you have here is you present a screen with a list of values that you will need the user to enter. Usually this entails that once the data is entered, it will be saved to a data file, or a database. You'll see later that there's more than one thing you can do, at the field level (for each value to be entered) to avoid errors caused by human interaction. Some forms will need certain values to be entered before another for the sake of being able to identify certain factors before giving the user field related help. Not all forms need a field level validation however.

Form Level Validation:
Same scenario as above but no field need to be entered before any other fields on the form. This usually means that the user will enter the information and validation is done once, for the whole form, usually before a save of the information is needed. Most of the time, client information screens and other general information inquiry screens can do fine with a simple form level validation as described here. They just need to make sure that mandatory fields are provided by the user and the rest of the information generally of the expected type or empty (if any field can be considered optional.

Data Saving Validation:
This type of validation is performed at the routine that will be performing the actual saving of the information to the file or database record. This is usually used in option screens or multiple data entry forms that all need to be entered before the record is physically saved. For example, an option screen typically has tabs offering more than one page of information that can be set by the user. The usyer can go to any and all of these tabs, change the values that are needed to be changed and the data gets saved once the user presses a "Save" or "Ok" button of some sort.

Search Criteria Validation:
Some may feel that this type of form (a search for form) can do without data validation. When you think about it. Think of the time saved, if you could help make sure that results were actually returned and that those results were relevent to what the user is looking for to a certain degree. In many cases this might not be important per se, but I like to believe that in other cases, this type of validation would be well sought after and most definitaly appreciated by the users of your application.

Many times people just don't bother implementation data validation at all while they are creating their application and this usually results in very bad things happening that really could have been avoided with proper data validation. In a big project, the right data validation should be established at the screen design phase of development as this is where you'd usually have time to talk about the role of each form and how important the data validation would be for the given forms. Let's see now what is available as far as tips and tricks to help eliminate or atleast minimize the risk of error in your application.

REMOVING/MINIMIZING HUMAN ERRORS:

As mentionned, there are ways around data validation. Ever heard the expression "prevention is the best policy"? Well as far as data validation is concerned, this saying definitaly applies. The best place to prevent human error is of course at the data entry screen level. From there, giving the user the right means of entering his data can, in most cases, eliminate the need for data validation. Indeed, a good data entry screen will be equipped with all that's needed to validate the data long before it can become dangerous to other parts of the application. Depending on the datatype at hand different types of field specific validations can be made available for different purposes. Let's see the different techniques and I'll explain what kind of data they apply to and how to effectively use them.

Range Validation:
As you might have guessed, this usually applies to numeric values or even dates. They perform a test to make sure that a value entered is within a range of specific values. Note that this could apply to characters as well. For example say you're making a questionnaire application that offers multiple choice questions wouldn't be of much use to accept Z or any other letters if the only choices are A, B, C, D or E. If there is a reason to have a minimum or maximum value, of any data type, then a range validation routine would become mandatory. Another example is say you have a field that expects a numeric entry. You could code to only accept numeric keys, the decimal point and the minus sign and reject the rest of the keys.

Lookup Validation:
Typically, this type of validation is done when a value entered needs to be compared to a list of possible values. A good example that relates to our Mortgage calculation program is the number of compounding periods per year. Most financial institution would need something like 1, 2, 3, 4, 6, 12, 24, 26, 52 and 365 (or 366 for leap years) in this case, a lookup validation would take the value entered and compare it against that list of values to report if it's a valid entry or not. Of course, the best thing you can do is not let the user enter invalid data to begin with. Perhaps a drop down list offering the choices would be good, this way the user can only select a valid value and therefore no validation per se is needed for this field. Anytime you can integrate something to force the user (so to speak) to have no choice but to enter valid data only, I would encourage to do so because you can be 100% sure about those fields and not have to worry about them for any other parts of the application as well.

Masked Input Validation:
As a list of examples, a telephone number, a zip code, a social insurance number and a UPC code all have one thing in common, they have a specific Input pattern that should be respected when entered and when read to assure that the right information is read from the user and written to file. Masked or filtered input is the art of only allowing valid characters to be entered in an otherwise all opened data type, in this case, a string. typically, masked input is present to give the user an indication of the type of information is required by guiding them through the process of entering the value in a field. Visual aids could also be used for example, if a date is expected in a given field value, perhaps a little popup[ calendar to let the user pick the date to be entered visually would be good since it would then be impossible to select an invalid date from a calendar. This is but an example. There are different situations as well. Taking the time to consider these little aids in entering the expected data properly will help your application work the way it should.

The best thing I can say at this point is to use common sense when evaluating the need for data validation. Typically it's not worth implementing data validation on small projects that you'd make for yourself because since they're your creations, chances are you'll know what data you need to enter and you can deal with the consequences of wrong data. For a game (depending on how widespread the game is) you might want to consider it for the sake of not having to answer repetitive questions that not having data validation might give you. For business applications and commercial applications of any type, you'd usually want to be as sure as possible about data validation. There's no room to mess around in the commercial application industry and if you can't be sure of what you are acquiring from the user, how can you garantee the results for the businesses that will be using it? Inserting data validation where appropriate only lifts your application's overall quality to a higher level and in today's computer world, any level higher is an excellent thing, it gives your application the edge it needs make itself worthy of considerations by those that will need an application like yours.

Many developers today already have libraries, in many languages, to take care of atleast part of the data validation process. Some even offer them for use in your own applications so you could find them and download them for your own needs if you don't want to code for them yourself. Me I like to use data validation in any project, even those I do for myself I try to put myself in the user's shoes, think of how I'd like to see things done and then make it happen. Sure when you're creating the application (even those for yourself) you might think I'll always know what goes where, but think of what if life gets you out of using that application for a couple years and you get back to it then. Would you remember everything that goes everywhere? The moral of the story is data validation can even protect you from yourself.

THE FINAL WORD:

And there you have it. Another aspect of the development process explained clearly, I hope. For an ending word, I can say that data validation, in many cases, has helped me even in ways I didn't think it could. I think we've all heard about the KISS development method (Keep It Simple and Stupid) and data validation is one of the best tools you have to help keep things simple, for the potential users of your application. Of course, the simpler you make it for your users, usually, the harder (and consequently the longer) it is for you to create the solution. That goes without saying but the rewards of such an effort are greater than the effort you put into the data validation process. Users will like your application for one thing. But they will also tend to use your application correctly as well which results in less support phone calls and emails and that should always be your ultimate goal, to make something that won't cause you to have to stay up all night answering questions about your application.

Like everything else I write, I can only hope I was clear enough. If I wasn't I would like to know, that's how one betters himself after all. So if there's a part of this article that just doesn't seem clear to you, email me, I'll see what I can do to make it as clear as it can be and that will be added/altered in this document to help make it as clear as possible. Happy coding.

MystikShadows
Stéphane Richard
srichard@adaworld.com

Download a copy of this tutorial.

PROPER ERROR MANAGEMENT IN FREEBASIC

Written by Stéphane Richard (Mystikshadows)

INTRODUCTION:

Don't be scared by the title. Believe it or not, it's amazing the problems that can be solved just by taking the time to implement a proper error management system into your code. Error management is often overlooked today no matter what platform your projects are intended. Why you ask? Simply because it is seen as a big beast to implement. This is usually because many coders who claim this tend to implement error management after the game or application is developed already. Indeed, to have a good control over the error management system, it needs to be implemented before and during the coding of the application, not after. Then, you'll see, error management won't be the big beast it is claimed to be.

This article will attempt to cover error management as it could be implemented in FreeBasic as well as see how to manage the errors themselves. Indeed, the application doesn't need to be halted everytime an error occurs, we'll see why here and what you can do instead of halting the program.

WHAT EXACTLY IS ERROR MANAGEMENT:

The best way to explain this concept is to start by defining what an error is in this context. In this document we'll be covering the runtime errors not the syntax errors because the compiler reports those errors so you can correct them. Runtime errors are, well, errors that happen while your program is executing itself. Error management is the art of controling these runtime errors, reporting the problem and taking the proper action for these errors. The first thing I need say is that I split errors up into three general categories. There are the software errors, operating system errors and the hardware errors. Let me explain these:

Software Errors:
These are errors that were caused by the program itself while it was performing a task that didn't need any hardware to perform. These could be mathematical errors such as "Division by zero error" or any other non hardware related errors. When you run out of memory or stack space are other good examples of these errors.

Operating System Errors:
These are errors that are typically caused when the program attempts to access a device but fails to for whatever reason. They are also created when, for example, you open a file that does not exist, or do not have the rights to write to the folder you are trying to create the file to. These type of error usually entail that there's no hardware failure, but the operating system itself is not letting you do the expected job.

Hardware Errors:
These errors, as the name implies are hardware caused. Printer is not ready error is a good example of such error. when you try to access drive A but there's no floppy in the drive, I also consider that a hardware error because if a floppy was present, everything would go smoothly. This could be true if you're trying to set a graphic mode that simply isn't supported by the hardware present in the computer too. Basically any error that is caused because a hardware device is not present, or not performing it's designated task when asked to is, to me, a hardware error.

The reason why I split the errors that can occur into these three categories is mainly to split the error management task into 3 simpler functions. It is also because I treat these three groups of error differently. Like I mentionned, not all errors need the same kind of management nor do they need the same type of exit procedure. The art of deciding which method to use and when to return to the program itself and when to halt everything and go back to the operating system is what proper error management is all about.

WHAT TO DO WHEN AN ERROR IS ENCOUNTERED:

Again I can only share what I know and what I use. So in a typical error management scenario, what you'll see here is how I would cope with the situations. When you get an error, in freebasic and alot of other BASICs i'm familiar with, the error number of the problem can be found in the Err variable. First thing I do is look up the error in a table like this one to know what exactly the error actually is. Then according to the error number, I have the application report the error (if needed) and perform certain recovery functions (if needed) and finally the application can continue (once all the precautions are taken). Here's a rundown of these situations, and what could be done with them. Atleast, it's what I'd do when I encounter them. This is a list of circumstances that could potentially cause errors and what one could do with them. These are suggestions (as in what would/could be considered proper thing to do) in some cases, you might need to halt on every error (really depends on the nature of the application).

Mathematical Errors:
The more classic example is the infamous Division by Zero Error. However there are many reasons such an error would occur. When your application is heavily mathematical, you need to control the flow calculation. Maybe a variable, that should have received a result prior to another part of the set of calculations or formulas, was set yet, Perhaps another error somewhere else in the code wasn't executed. The main thing to ask yourself when mathematical errors are created is how bad it is for the application. Typically, all erroneous results from a formula needs to be reported. However exiting the application abruptly would be overkill in this scenario. The best thing to do is report the error and cancel the operation allowing the user to see if what he did before calling the formula isn't part of the problem (a field that was not entered or validated for example). Basic rule of thumb is if you know which variable doesn't have it's value set, when you're reporting the error, you should add it to the error reporting, it will help the programmers decipher where the error came from better.

File Access And Manipulation Errors:
You try to open a file and for some reason it won't let you (file not found, File is Read Only (and you're trying to open it to write to the file) and other such errors. This could happen when you physically select a file in a Save or Open dialog. Access Denied Errors could be because you have the file open by another application or someone else on the network opened it. If you hard coded a network path and suddenly the network drive isn't available. There are many situations why a File Access or Manipulation error can occur. It's not a good idea to exit the program abruptly here either especially when the user is just opening a file (they could open other files if the need to so there's still work that can be done even if they can't open the current file. They should be given the option to do so in this scenario. One situation that would be valid to exit the application is if the program needs to connect to a database for any work to be performed then there's no point in staying in the application. You could stay at the beginning of the application to give them a chance to fix the reason why it can't connect to the database, but it would be the same results just exiting the program, then they get the problem fixed, and restart the program.

Network Related Errors:
The reasons why a network error of some sort would happen usually are similar to the situations that would cause file access and manipulation errors. The file doesn't exist, the network drive isn't mapped (in the cases where it needs to be) insufficient rights to perform the requested file or database operation and so on. Because you are in a network environment rather than working locally on your hard drives for example, some error should be treated differently. However, as a general rule of thumb, treating the as file acccess manipulation errors will be considered acceptable. The only thing that could change is if you can't save to a network file, an option to save locally could be added so the work done to a file isn't lost. Then when the network situation is resolved, you could ultimately tell the user and offer to copy the local files to the designated network location.

Peripheral Access Error:
Well this one pretty much speaks for itself when you think about it. Try to write your file a write protected floppy disk for example will cause this type of error. Trying to print a document and the printer isn't ready (no paper, printer is not on, a paper jam has occured) whichever the reason may be, again here cancelling the current operation and offering to start the operation again when the error is fixed is usually the best policy, the civilized policy so to speak. Most of the time these error numbers and description will be able to tell the user what happened and give them a good idea on how to fix the problem so the operation can be carried out successfully. if the drive has bad sectors it will be reported and in some cases it would be useless to try the operation again. In those rare cases, exiting the application could be tolerated if there's no alternatives to the error.

Internal System Errors:
There's two types of internal System Errors. Out of memory errors can be managed in a civilized manner, however Memory leak errors should be reported and the application halted in some way. Before you'd have the option to have a floating point coprocessor present in the system or not. Back then, if your program relied on a mathematics coprocessor to perform an operation and it wasn't present it would be considered an internal operation error. If only that part of the application needs that special function call, you could cancel that process and return to another part of the application (usually the place that caused the error) and let the user do other things otherwise, I usually exit the program as in the current context of the application, the desired operation will never work until such a time where they either add memory to the system, upgrade their hard drive and other situations that will, beyond a shadow of a doubt, need to restart or reboot the system.

Typically, these are the errors you need to be careful and pay special attention to. There are other types of errors but usually they can be handled without being reported. How you treat these errors will vary based on the importance of the situation or the part of the application that is causing the error. If you're saving you'll want to give a few options to see if there could be a way to not loose the file for example. As files are usually quite important and typically not created just for fun. Now that we know the types of errors and the situations and circumstances that can cause them, we'll now look at what good error management could be at the level of the language itself, in our case, FreeBasic.

HOW TO CODE FOR THE ERRORS IN FREEBASIC:

The first thing to know about coding for error trapping and management is what the language offers as tools for error control. In the case of FreeBasic, errors are trapped as events so to speak and a series of statements are provided to manage them. Let's start by looking at an empty skeletal code sample to start to situate where things go. In FreeBasic errors are best managed at the sub or function level. So hor first example will be a function example.

FUNCTION OpenDatabaseFile(FilePath AS STRING) AS INTEGER

    ' -----------------------------------
    '  First we Turn On Error Management
    ' -----------------------------------
    ON ERROR GOTO ErrorManager
    ' --------------------------------------------------------
    '   Here we put the code that the function should perform
    ' --------------------------------------------------------
    OpenDatabaseFile = 0

    ' -----------------------------------------------------
    '  When we're exiting we can turn off Error management
    ' -----------------------------------------------------
    ON ERROR GOTO 0
    ' -----------------------------------------------
    '  We now need to exit the function so the error
    '  manager part isn't executed accidentally
    ' -----------------------------------------------
    EXIT FUNCTION

ErrorManager:
    ' ---------------------------------
    '  Error Management Code goes here
    ' ---------------------------------
    RESUME NEXT

END FUNCTION

Now let's see what we have here. The first line in the function turns Error trapping on so to speak by telling the program that if an error occurs, go to the ErrorManager label to execute the code that's there. After that first line goes the code to what the function should be doing. Here I just assign 0 as the return value of the function. But the actual opening of the database would have been right before that assignment. Next we turn error management off with the ON ERROR GOTO 0 <- (zero). This is how you turn off error management in FreeBasic (and most basic dialects today). Since in FreeBasic error trapping is at the sub or function level you can omit this line as it will be turned off at the end of the subroutine. We then exit the function with EXIT FUNCTION. I can stress the importance of that EXIT FUNCTION statement. If it is not present the code will naturally continue all the way to the label ErrorManager and execute that code too because it's part of the function. So you need to exit the function before the program gets a chances to get to that error manager. If an error Occurs, the program will jump to that label and execute the code, that's the only time you'll want to execute that code. Finally the error management could should Resume execution of the program with RESUME NEXT if the error is critical enough to warrant exiting the program it should be done before the RESUME NEXT statement. We'll see examples of this later in this document.

Now let's put some code in here to see what we can do. Taking our sample function which would typically open a database file it's important to note that error management in FreeBasic or any other languages should be context sensitive. For example, if this function opens a database file, it wouldn't make sense to manage calculation errors like division by zero because you won't be calculating in this function. That's what I mean by you have to keep things in context. Here's some code.

FUNCTION OpenDatabaseFile(FilePath AS STRING) AS INTEGER

    ' -----------------------------------
    '  First we Turn On Error Management
    ' -----------------------------------
    ON ERROR GOTO ErrorManager
    ' --------------------------------------------------------
    '   Here we put the code that the function should perform
    ' --------------------------------------------------------
    OpenDatabaseFile = 0

    ' -----------------------------------------------------
    '  When we're exiting we can turn off Error management
    ' -----------------------------------------------------
    ON ERROR GOTO 0
    ' -----------------------------------------------
    '  We now need to exit the function so the error
    '  manager part isn't executed accidentally
    ' -----------------------------------------------
    EXIT FUNCTION

ErrorManager:
    ' ---------------------------------
    '  Error Management Code goes here
    ' ---------------------------------
    SELECT CASE ERR
           CASE 2   ' The system cannot find the file specified.
                Message$ = "The system cannot find the file specified."
           CASE 3   ' The system cannot find the path specified.
                Message$ = "The system cannot find the path specified."
           CASE 4   ' The system cannot open the file.
                Message$ = "The system cannot open the file."
    END SELECT
    PRINT Message$
    OpenDatabaseFile = Err

END FUNCTION

As you can see, I only manage file related errors and that is the way it should be as well. This is a basic error manager in that it only displays the error that just occured and exit the subroutine, not the whole program, just the faulty function. The code that called this function would either continue with the code or stop should the error justify it. You can use error management to provide alot more information that this however (which is useful, for instance, in a testing and debugging session) where the aim of the error management isn't only to trap errors but to fix them whenever possible). Here's the same code with a bit more useful detail if you wanted to search for the bug.

FUNCTION OpenDatabaseFile(FilePath AS STRING) AS INTEGER

    ' -----------------------------------
    '  First we Turn On Error Management
    ' -----------------------------------
    ON ERROR GOTO ErrorManager
    ' --------------------------------------------------------
    '   Here we put the code that the function should perform
    ' --------------------------------------------------------
    OpenDatabaseFile = 0

    ' -----------------------------------------------------
    '  When we're exiting we can turn off Error management
    ' -----------------------------------------------------
    ON ERROR GOTO 0
    ' -----------------------------------------------
    '  We now need to exit the function so the error
    '  manager part isn't executed accidentally
    ' -----------------------------------------------
    EXIT FUNCTION

ErrorManager:
    ' ---------------------------------
    '  Error Management Code goes here
    ' ---------------------------------
    SELECT CASE ERR
           CASE 2   ' The system cannot find the file specified.
                Message$ = "The system cannot find the file specified." & _
                           "In the OpenDatabaseFile Function with " & _
                           FilePath & " Passed as a parameter."
           CASE 3   ' The system cannot find the path specified.
                Message$ = "The system cannot find the file specified." & _
                           "In the OpenDatabaseFile Function with " & _
                           FilePath & " Passed as a parameter."
           CASE 4   ' The system cannot open the file.
                Message$ = "The system cannot find the file specified." & _
                           "In the OpenDatabaseFile Function with " & _
                           FilePath & " Passed as a parameter."
           CASE ELSE
                RESUME NEXT
    END SELECT
    PRINT Message$
    OpenDatabaseFile = Err

END FUNCTION

You can be as detailed in your explanation of the error as you want. The important thing is that adequate information should be reported with the error to help correct it. If there's more than one thing that could happen in the process of performing an operation, you could write these errors to a log file so that all the details of the operation can be recorded and studied at a later time for possible correction. The CASE ELSE clause is telling the program that if any errors that aren't 2, 3 or 4 occurs, just continue with the normal execution of the code. I would say that the best thing to do is to use common sense and what you feel should be done. If you are using an application and you don't like the fact that the program stops everytime an insignificant error happens, then you need to assume that most people shouldn't like it if your program exits for the same reasons. Indeed a good way to learn is to see how other (popular and well known) programs handle their errors and to mimic them basically. If it's good enough for the others it should be good enough for your projects.

What can you learn from this? When you manage your errors, while you are coding (not adding error management to the project) the task doesn't look as bad and yet it requires the same amount of work. Usually, I have code snippets for all my error management situations and I just paste the appropriate code in the appropriate sub or function. Saves alot of typing and makes error management quite easy this way especially if the project is a big one. You can create standards this way that others can follow which also helps manage the overall quality of the whole project just by having a certain control over the errors that could occur even if the fault is that of the programmer.

AND IN CONCLUSION:

And this concludes our technique on proper error management. As you can see from the short code samples here, error management can represent a good part of the programming process. The more errors a sub or function needs to manage, the longer the error management part for that function or sub will be. And because that, you can imagine what a job it can be to add after you coded the program. It's doable but it's a big chunk of coding in itself if kept for the end of the programming phase.

Functions that perform calculations don't all need error management either. If you don't divide a variable by another in that function, you'll never cause a division by zero so that function can be spared the error management code. You have to take the time to see what the sub is doing, and what could go wrong when it does it's job. That's why common sense is of the essence. As always I'm opened to comments, suggestions and ideas about this document. Feel free to email me, as always, with any questions. Until I write again, have a good error free program.

MystikShadows
Stéphane Richard
srichard@adaworld.com

Download a copy of this tutorial.

Artificial Intelligence, Real Intelligence and QBasic,

Written by Robert Hambly

Disclaimer: The following article and program are very much a work in progress. They are offered for publication because today is a deadline. The article was dictated last night using a DS-2 Radio Shack Voice Recorder into Word 2003. The program was converted the day before from ancient Basic code (GW Basic and others – circa 1970’s and 80’s).

There are some websites created today to support AI and QBasic. They are available by sending an email stating your interests to me (roberthambly2000@hotmail.com). One site is for support for this QBasic AI Program. One is support for Writing with a Voice Recorder, and one is for discussing Writing Articles in Computer Legible Form (using bold face and underlines for noun phrases and verb action items). Please put the words AI in the subject line of your email so I can attend to it appropriately.

The enclosed QBasic program is a working model using a multilevel nested tree data structure similar to those used in artificial intelligence. This one is a very user friendly data structure, perfect for children of all ages. It can immediately tell stories using the data you have formatted.

The stories can be in color, and used to prompt children and help them read. It can also be used to help adults clarify and define their goals, write thank you notes, and even perhaps write a love stories.

You might take a minute to look at the data structure and think about what output is produced. As you read further, you could begin thinking about how you can start to represent something important in your own world.

Artificial Intelligence

Artificial intelligence programs, especially programs working with natural language, usually have three parts:

An input parser, that attempts to understand human input.
Large knowledge structure representations of information that can be utilized by the computer when mixed with the natural language input.
An output generator which takes the new internal representations, and create sentences for humans to understand.

Most work in artificial intelligence has been done in Lisp or Logo, but as you see in the program enclosed, simple knowledge representation can be done in QBasic, at least with properly formatted QBasic data structures.

Your Intelligence

Anyone reading this article possesses some intelligence, and probably a lot of the particular kind of intelligence common to mathematicians or programmers.

It is interesting to explore your own intelligence. What do you think? How do you think? What are your value system coefficients? How do you represent what you believe? What do you know or understand? And how can you use computer representations to move our understandings of ourselves and each other forward?

The enclosed program is a simple system that allows you to begin representing any piece of knowledge you have. The structure consists of multilevel data symbols, where you can have as many labels for an idea as you wish.

Representing Intelligence

Right now the program mostly represents you. It relies entirely on you for input, and your gradual clarification (editing) of its symbol (word phrase) definitions from which it generates random output.

The output is in the form of simple stories, generated by a random selection of different components (words or phrases) under your variables.

As you’ll see if you study the data structure, simple sentences describing who you are, or what you like, can be displayed in different ways.

Complex Sentence Structures

The simple examples however don’t in any way exhaust the ultimate powers represented by these structures.

You do not need to use declarative sentences. Any linguistic structure (in any language) can be used. Anything that you can define or label, the computer can “understand” and then look up your definitions, select randomly from your details, and either display your words or find other symbols to look up further.

The discipline for the programmer is to clarify his understanding, her expertise, her world, or her understanding of the child’s world.

Whether you’re interested in investments, computer games, recipes, football, or mysticism, if you can talk about it, the computer can tell stories about it.

Recursion via a Stack

The program works by allowing recursion through a simple internal stack structure. The current program was re-written from programs written for old Atari computers, where there were recursion limits built into subroutine calls by the compiler.

We chose to implement our own recursion routines as a simple array stack, rather than restrict the depth of our subroutine calls. We put sentences on the stack and pulled phrases off the stack as we moved up and down levels so that we could generate reasonable size stories.

QBasic has a good level of subroutine recursion (programs repeatedly calling themselves), so that any further programs we write may well use familiar Lisp or Logo structures for recurrence with subroutines and functions calling themselves (see the ButFirst Example, Line 80).

Program Operation

The program as it currently stands offers very simple data abstractions. The code is small, and should be easy to understand. Some debugging code was left in place so you can look at the internal operation anytime you wish to see what is happening, or why your new script isn't running.

The most common problem you will have with adding new elements of the script (DATA statements), is not following each group with a blank DATA statement or now having the Z. symbols spelled perfectly and exactly the same everywhere, matching in upper and lower case letters.

You can copy and paste this program right now into QBasic, and it should run perfectly. Then you can start editing your data structures, and immediately start producing stories so that you see your personal functionality. You can engage in the discipline of modeling yourself, your favorite games, your best friends, your goals or desires, and create some new interesting ways of telling your stories.

From the web, you can use the mouse to select the entire program from this web page, copy and paste it into notepad, save it as a .txt or .bas file, load it into QBasic (or beyond), and start editing. The data you use will begin to represent your world, your word phrases, even your current language preference. If you speak another language, so does your program.

Symbols

Symbol definition and manipulation is one of the foundational arts of artificial intelligence since humans deal in symbols. Words for word phrases are the easiest symbols for QBasic to represent.

We differ from each other in our understandings of those symbols, in terms of the data structures underneath the symbols that represent the meaning or understanding of those symbols. We also differ in the value system coefficients we place on the symbols in terms of whether they are true, or beautiful, or good, or important, etc.

The symbols in this QBasic program are defined simply by beginning a word phrase with two characters 'Z.’.

Different Colors for Different Symbols

To add interest, and visual variety, as well as identifying multiword phrases, we’ve included the ending '.C' QBasic color number to the symbols.

Right now when the computer looks up a value for a symbol in the six or eight items below the symbol in the DATA table, and randomly selects an item, it will color the text found according to a QBasic color number found after the '.C'.

All words in a phrase within the symbol definition are colored the same color. When the value for the symbol has been printed out, then the color is returned to QBasic color seven.

Five Parts of Five Programming Style

The program has been written in a modified five parts of five programming style. This program has been rewritten, from several old basic programs. And although it has been tested on several current scripts, it is still far from perfect.

In old GW basic, my programming used odd numbers for main functioning code, using 1 for Introduction, 3 for Input, 5 for Work, 7 for Output, and 9 for Control. The even numbers were for less important material, or poorly thought out material. 1 or 10 of 100 or 1000 had the same broad function, but reflected a different level of detail.

Modern subroutines and other structured programming techniques make this kind of structural definition less necessary, but these modern techniques also don't immediately flag the level or priority of the subroutines within the program.

The old GW basic would not allow material between the line numbers. QBasic gives us that option. I have left the number labels mostly intact, so that you can see how this extra material is still roughly organized within the five parts of five system.

This five part structure has also been useful in other academic areas, for writing, for thinking about problems, and even for programming with other computer languages.

Suggestions for Program Additions

There are many obvious additions that can be made to this program. The most immediate additions would include:

reading data from a text file. (using Line Input #1 for the a$ data array),
story capture to text file (using Print #2 to CLIP: for clipboard paste),
symbols as actual programs (using an if Z.Symbol then gosub structure).

Routines can be added while still preserving the Five Part Structure by renumbering the code up to 100 - Initialize, 300 - Input, 500 - Work, 700 - Output and 900 - Control areas. This would allow more room for code while preserving an over all picture.

Programming within these larger numbers, allows more room to continuously upgrade the routines while leaving overall functional descriptive labels intact. This means someone reading or maintaining the program in the future can still preserve the label system organization of the program reflected by the numeric label each segment has.

There have been many programming structure systems developed, and if people suggest improvements to this code, I will try to preserve this label numbering system, so we can look at each other’s work quickly and understand easily where each new piece fits.

Roger C. Schank

If people are interested in artificial intelligence, and exploring Lisp or Logo like structures in QBasic, then I will be using books by Roger Shank for his style of conceptual information processing. I have some old material already written and will convert this to a tutorial format.

The specific book we will study and represent within QBasic is a book published in 1981 called Inside Computer Understanding - Five Programs plus Miniatures.

He has elaborate nested tree data structures that represent meaning in his conceptual dependency terms.

Many of these are simple structures to understand at the outset. We may begin a series of tutorials next month if there’s interest in this subject.

Children Stories Now

Right now you can use the program to generate some simple stories, especially children stories. The program is perfect for children learning to read.

You can attempt to model your child’s world. You can see her games, his friends, and you can use different colors for the words that describe these favorite items.

Children can then read stories about themselves and recognize words and phrases within their lives.

Adult Stories

Certainly adult goals, vacation plans, sermons and projects can begin to be represented.

Indeed any subject people are talking about can probably have a representational discipline added. You can start thinking about representing the world of anyone around you in these detailed symbols.

Yes, of course, you can be used this program to represent adult stories, in the full sense of that word.

As you find you enjoy romantic themes or other kinds of adventures, you can represent those through whatever level of abstraction you choose. Then you can have the computer tell you stories prompting or suggesting other aspects or combinations of the material.

AI QBasic Web Site

Everyone is busy, and the future of this program or of artificial intelligence and QBasic is up to us.

I will be maintaining a web site that will include detailed scripts for this program that we’ve already done, and can possibly make the best scripts available here in this newsletter.

I will make this AI QBasic Web Site available to those who send me e-mail with some thought either about AI data structures, about this little program, or about the future of computer understanding in general.

The websites are currently password protected, but I will make them available to anyone who shows he or she is serious about thinking about their thinking.

So Write Some Code (or Edit a Script)

The bottom line in artificial intelligence programming is that you must have a program. Theories, descriptions, ideas, must be somehow represented in computer code.

This program allows any words you can think of, any data, any symbolic abstraction hierarchy you can create to be represented in the computer

The discipline of continually adding depth, adjusting the symbols, redefining the symbols, and eventually adding program capacities to your symbols, as is available in Lisp and Logo, means that there’s no excuse for not beginning your work now.

Copy the program into QBasic, run it, change it immediately into something that’s real to you, and begin to add some depth to your new representation of you, and make plans to share that on the web.

Thanks to Pete and his newsletter for the opportunity for presenting this material.

Robert Hambly

AI Ed(ucator)

roberthambly2000@hotmail.com

QBasic Story Program

Download the QBasic Story Program (17KB, txt format) that accompanies this article.

Coding A Parallax Scrolling Platformer
Chapter #1: INTRODUCTION

Written by Na_th_an

Hello people! I've been suggested by a couple of friends that I should create yet another tutorial series, this time in something less complex yet equally challenging: parallax scrolling platformers. So I've decided to give it a go. Don't worry, this won't become an encyclopaedia like the IF tutorials, we all know that parallax scrolling platformers are way more simple to code. Oh, what are you saying? That you didn't know that? Well, once you finish with this series you'll be able to assure that. You can code this engine in one afternoon when you know what you are doing.

What we are coding

First of all let's define the kind of engine we are going to build:

Maps are composed by a grid of equally sized "tiles". In this example, we'll use 16x16 tiles, which is (in my humble opinion) the optimal size for a lo-res game.
Maps will be way larger than the screen, so we'll use a nice and smooth parallax scrolling with two planes. Adding more planes is trivial, so I'll show you how to do it for two planes and then you can add as many extra planes as you want, once you get how it works.
The player will have smooth movement using simple "accelerated linear movement" physics in 2D. You'll learn how to deal with things like gravity and friction. Good news: you won't need to know trig, but it would be nice if you understood what "velocity" and "acceleration" mean, and some cinematic equations.
We'll add nice semi stupid enemies using simple Finite State Machines and function pointers. This is a good chance to learn how to work with function pointers!
We'll discuss on what to focus your game on: shooting, collecting treasures, jumping on top of baddies to kill them...

Until now, I've tried to give you code snippets that would work with both QB and fB, but this time this is impossible. The built-in QB graphics routines are far too slow and too limited for this, plus I could not be using function pointers. Instead of having to choose a third party graphics library for QB, I prefer to go for fB and stick to Angelo's GFXLib which everyone has and everyone should be familiar with.

What we need

Well, first of all, the latest release of freeBasic, which I'm pretty sure you know where to get form, but anyways, follow the arrow -> http://www.freebasic.net.

You need to create some graphics. Get a nice tool, one you feel comfortable with. You can use whatever you like. In this tutorial, I'm gonna show you how to store all your gfx in a GIF file and get them from there, instead of having a single sprite file for each sprite/tile or having to use strange PP256 subroutines and hacks. You can, of course, rip the graphics from various resource sites if you feel happy with it.

We are gonna use FMOD for sound, so it would be nice that you had the latest FMOD.DLL file lying somewhere where it is accessible (the /WINDOWS/SYSTEM32 folder, for example).

Be sure to download Paint Shop Pro 3.1 from here -> ftp://ftp.kemmunet.net.mt/pub/software/win3.11/utilities/psp311.exe or any other program which is able to save GIFs in the "GIF87a" format, as we'll be using Rich Gieldreich's loader which sometimes has problems with "GIF89a" files. This is the GIF loader we'll be using. Copy it into an empty text file and save it as giffb.bas. We'll use it as an external module all the time:

' GIF loader and decompressor by Rich Geldreich/
' ported to FB by na_th_an

' Disclaimer: Mr Geldreich wrote the most ugly code out there.
' This has been beautified a bit by yours truly, but I did not
' spend so much time.

' You may want to remove "screenlock" and "screenunlock" from
' the LoadGIF Sub.

' To use this in your program, just add:

' Declare Sub LoadGIF (xx%, yy%, gif$)

' To the top of it, and don't forget to add this .bas file
' to your compiling line, i.e.

' $ fbc mygame.bas mymodule.bas gifloader.bas -s gui

' BTW, this SUB just loads GIF87a, non interlaced GIF files.
' Most modern program use the GIF89a standard, which is NOT
' supported.

' If you don't have a program that exports to GIF87a, you can
' download Paint Shop Pro 3.12, which helps you converting
' from GIF89a to GIF87a.

' Paint Shop Pro 3.12 can be downloaded from:
' ftp://ftp.kemmunet.net.mt/pub/software/win3.11/utilities/psp311.exe

DEFShort A-Z

Declare Sub LoadGIF(xx%, yy%, gif$)
Declare SUB Plot (A)
Declare FUNCTION Getbit ()
Declare FUNCTION ReadCode (CodeSize) as Long

CONST True = -1, False = 0

DIM Shared ByteBuffer AS STRING * 1
DIM Shared Powers(8), Prefix(4096), Suffix(4096), Outcode(1024), CodeMask(8)
DIM Shared MaxCodes(12), Powers2(16), Pal(255) AS LONG
DIM SHARED Xstart, Xend, X, Y, Xinit, Yinit
Dim Shared Bitsin, BlockLength, Num, TempChar
Dim Shared ffHandle%

GifData:
DATA 4,8,16,&h20,&h40,&h80,&h100,&h200,&h400,&h800,&h1000,8192
DATA 1,3,7,15,31,63,127,255
DATA 1,2,4,8,16,32,64,128,256,512,1024,2048,4096,8192,16384

Sub LoadGIF(xx%, yy%, gif$)
	dim red as long, green as long, blue as long
	dim palcolor as long

	ScreenLock

	Num = 0: Bitsin = 0: BlockLength = 0

	Xinit = xx% : Yinit = yy%

	Restore GifData
	FOR A = 1 TO 8: Powers(A) = 2 ^ (A - 1): NEXT
	FOR A = 0 TO 11: READ MaxCodes(A): NEXT
	FOR A = 1 TO 8: READ CodeMask(A): NEXT
	FOR A = 0 TO 14: READ Powers2(A): NEXT

	F$ = ltrim$(rtrim$(gif$))

	ffHandle% = Freefile

	OPEN F$ FOR BINARY AS #ffHandle% LEN = 1

	FOR A = 1 TO 6
		 GET #ffHandle%, , ByteBuffer: A$ = A$ + ByteBuffer
	NEXT

	GET #ffHandle%, , TotalX
	GET #ffHandle%, , TotalY

	GET #ffHandle%, , ByteBuffer: A = ASC(ByteBuffer)
	BitsPixel = (A AND 7) + 1

	GET #ffHandle%, , ByteBuffer: Background = ASC(ByteBuffer)
	GET #ffHandle%, , ByteBuffer

	IF ASC(ByteBuffer) <> 0 THEN
		 PRINT "Bad file."
		 Goto EXITSUB
	END IF

	FOR A = 0 TO 2 ^ BitsPixel - 1
		 GET #ffHandle%, , ByteBuffer: Red = ASC(ByteBuffer)
		 GET #ffHandle%, , ByteBuffer: Green = ASC(ByteBuffer)
		 GET #ffHandle%, , ByteBuffer: Blue = ASC(ByteBuffer)
		 Red = Red \ 4
		 Green = Green \ 4
		 Blue = Blue \ 4
		 palcolor = Red or (Green shl 8) or (Blue shl 16)
		 palette A, palcolor
	NEXT

	GET #ffHandle%, , ByteBuffer
	IF ByteBuffer <> "," THEN
		 PRINT "Bad file."
		 Goto EXITSUB
	END IF

	GET #ffHandle%, , Xstart
	GET #ffHandle%, , Ystart
	GET #ffHandle%, , Xlength
	GET #ffHandle%, , Ylength
	Xend = Xlength + Xstart - 1: Yend = Ylength + Ystart - 1

	GET #ffHandle%, , ByteBuffer
	A = ASC(ByteBuffer)
	IF (A AND 128) = 128 THEN
		 PRINT "Local colormap encountered."
		 Goto EXITSUB
	ELSEIF (A AND 64) = 64 THEN
		 PRINT "Image is interlaced!"
		 Goto EXITSUB
	END IF

	GET #ffHandle%, , ByteBuffer
	CodeSize = ASC(ByteBuffer): ClearCode = Powers2(CodeSize)
	EOFCode = ClearCode + 1: FirstFree = ClearCode + 2
	FreeCode = FirstFree: CodeSize = CodeSize + 1
	InitCodeSize = CodeSize: Maxcode = MaxCodes(CodeSize - 2)
	Bitmask = CodeMask(BitsPixel)

	GET #ffHandle%, , ByteBuffer
	BlockLength = ASC(ByteBuffer) + 1: Bitsin = 8
	OutCount = 0
	X = Xstart: Y = Ystart

	DO
		 Code = ReadCode(CodeSize)
		 
		 if eof(ffHandle%) Then Exit Do

		 IF Code <> EOFCode THEN
			  IF Code = ClearCode THEN
					CodeSize = InitCodeSize
					Maxcode = MaxCodes(CodeSize - 2): FreeCode = FirstFree
					Code = ReadCode(CodeSize): CurCode = Code
					OldCode = Code: FinChar = Code AND Bitmask
					Plot FinChar
			  ELSE
					CurCode = Code: InCode = Code
					IF Code >= FreeCode THEN
						 CurCode = OldCode
						 Outcode(OutCount) = FinChar
						 OutCount = OutCount + 1
					END IF
					IF CurCode > Bitmask THEN
						 DO
							  Outcode(OutCount) = Suffix(CurCode)
							  OutCount = OutCount + 1
							  CurCode = Prefix(CurCode)
						 LOOP UNTIL CurCode <= Bitmask
					END IF
					FinChar = CurCode AND Bitmask
					Outcode(OutCount) = FinChar
					OutCount = OutCount + 1
					FOR I = OutCount - 1 TO 0 STEP -1
						 Plot Outcode(I)
					NEXT
					OutCount = 0
					Prefix(FreeCode) = OldCode: Suffix(FreeCode) = FinChar
					OldCode = InCode: FreeCode = FreeCode + 1
					IF FreeCode >= Maxcode THEN
						 IF CodeSize < 12 THEN
							  CodeSize = CodeSize + 1: Maxcode = Maxcode * 2
						 END IF
					END IF
			  END IF
		 END IF
		 A$ = INKEY$
	LOOP UNTIL Code = EOFCode OR A$ <> ""

ExitSub:	
	ScreenUnlock
	Close #ffHandle%

End Sub

'This subprogram gets one bit from the data stream.
FUNCTION Getbit ()
	
    'SHARED 
    Bitsin = Bitsin + 1
    IF Bitsin = 9 THEN
        GET #ffHandle%, , ByteBuffer
        TempChar = ASC(ByteBuffer)
        Bitsin = 1
        Num = Num + 1
        IF Num = BlockLength THEN
            BlockLength = TempChar + 1
            GET #ffHandle%, , ByteBuffer
            TempChar = ASC(ByteBuffer)
            Num = 1
        END IF
    END IF
    IF (TempChar AND Powers(Bitsin)) = 0 THEN Getbit = 0 ELSE Getbit = 1
END FUNCTION

'This subprogram plots one pixel on the display.
SUB Plot (A)' STATIC
    PSET (Xinit + X, Yinit + Y), A
    X = X + 1
    IF X > Xend THEN
        X = Xstart
        Y = Y + 1
    END IF
END SUB

'This subprogram reads one LZW code from the data stream.

FUNCTION ReadCode (CodeSize) as Long
	 Dim Code as Long
    Code = 0
    FOR Aa = 0 TO CodeSize - 1
        Code = Code + Getbit * Powers2(Aa)
    NEXT
    ReadCode = Code
END FUNCTION

(Please don't complain for the above code, it is not mine - I just spent a bad time formatting it to make it, at least, readable. It looks like old time gurus didn't know shit about clean code :D But hey, it works and it's fast! - I would not have been able to code this with all my "clean code" to save my life - lol)

Also you would need a map editor which is able to save data in a raw way, i.e. 1 byte per tile and nothing else. I use mappy ( which can be found at http://www.geocities.com/SiliconValley/Vista/7336/robmpy.htm ), which is simple, easy to use, and small. You can use whatever you like, or code your own (I might have coded a map editor per game <- not a good idea, specially for lazy coders like me).

Breaking this into pieces

I always feel the need to have an schematic view of what I am gonna code, so let's overview which parts our engine will be composed of.

1. Initialization tasks

You know, load graphics and sounds, etcetera. This isn't something out of the blue, so we'll go accross this part fast. Basicly I'll explain how to stuff all your tiles in a GIF file and creating the sprites from there, plus how to load samples using FMOD and a couple of functions to wrap FMOD's so it's easier to deal with streaming background music.

2. Level loader

This part will depend on which map editor you use and the format it saves its files in. I'm using the binary export of mappy, which just saves every tile in the grid as 1 byte value, using row-order (this is, first 1st row, then 2nd row...), so my code will be prepared to load such kind of maps.

3. Camera movement / Map rendering

This is what makes the "parallax magic". This is so simple that fits in 10 lines and you'll be amazed on how easy it is.

4. Player movement

This is a bit more complex but nothing to be scared about. If you understand simple physics, you won't have problems with this. We will just building a "world" with gravity and friction and will move our player inside, following our own rules.

5. NPC movement

This will be the most interesting part, IMHO. It will cover finite state machines (FSM from now on) and function pointers, plus nice tricks to store all your enemies in an array.

6. Main loop

And this thingo will glue everything together. We'll begin building it (in a skeletal form) as soon as we begin coding, so you'll be able to "see things move" from the beginning.

Disclaimer

I have to make clear that, as always, what I try to explain only reflects my point of view and my way of coding. Maybe you disagree with some of my programming practices or my methods. I'm fine with that. This is just a way of doing something that can be done in a lot of ways, and that comes out directly from my researching and experiments. I'm pretty sure that you will find better ways to do some of the things I'll cover in this tutorial. If you think so, go ahead and write your own tutorial ;). The more, the merrier, they say.

Some data types and some introducing explanations

First things first. We need the correct data structures and arrays to contain the values we need for the game. The most important type structure is the PlayerType structure which will contain our main character's data and values. Our main character will move inside a 2D world, so the first thing we need is to store its position: x, y. We just said that our main charracter will move, so we need velocities, one for each direction: vx, vy. In each loop, vx will be added to x and vy will be added to y, making the player move. If vx is positive, the player will move to the right, if it is negative, the player will move to the left. Same with vy: if it is positive, the player will move down, and if it is negative it will move up. Note that we can have many different combinations of vx and vy resulting on diagonal and oblique directions.

As our "world" is 2D, we can break it into two axes: vertical and horizontal. As we'll explain later, horizontal and vertical movements won't interfere (although they happen at the same time), so we can deal with them separately. In the vertical axis, we have the strength that pulls the player down, i.e. gravity. Storing this value in the PlayerType structure will allow us to change it whenever we want (fancy a level at a moon base? then another one under the sea?). We also have the jump strength, which is the value that's substracted to vy when the player is pressing JUMP. Playing with these two values you can get very different behaviours when jumping. Big figures in both gravity and jump strength will make the character to jump very fast, allowing little horizontal movement while jumping. Low figures in both will make the character jump slower and fall slower, like under water, allowing a whole lot of horizontal movement. High gravity, small jumping strength will make the player heavy and the way around will make the player fly. Another value, "jumpmax", will limit the vertical speed we can get by jumping. If we don't use this, as long as we keep pressing JUMP the player will fly! We'll also need a flag to be set when jumping. Jumping is a bit complex and will be explained at a later time, when coding the movement routine. This has to do with the fact that the longer you press JUMP the higher the main character will jump (think of Mario or Sonic).

In the horizontal axis, we have linear movements with acceleration and friction. So we need two values: ax, or horizontal acceleration, and r, horizontal friction. When the player presses the left or right direction keys, the player gets accelerated just by adding ax to vx.when the player releases the key, in each loop we substract r from vx deccelerating the player. You can play with these two values to create fast running charcters, or icy floor (friction and acceleration very low!).

For animation we need two variables more: frame and subframe. The first one will carry which frame to render, the second one will be used to count how many game frames are between frame and frame. If we get our game to run at 60fps, maybe we don't want the animation in our main player to cycle at 60 fps, so we use "subframe". Letting subframe count to 5 before incrementing frame would make our main player animation run at 12 fps, for example. Also, a "facing" variable will be used to know whether the player is looking left or right.

Added to everything, we add a general purpose "flag" just in case we need it for something. Also, a pair "prevx" and "prevy" will be used to store the player coordinates before it jumps. That way, if the player makes a false jump and dies, we know where to reposition it.

The type structure ends as follows:

Type PlayerType
	x        As Integer		' x coordinate in pixels * 100.
	y        As Integer		' y coordinate in pixels * 100.
	vx       As Integer		' horizontal speed.
	vy       As Integer		' vertical speed.
	g        As Integer		' gravity.
	jump     As Integer		' jump strength.
	jumpMax  As Integer		' jump max speed.
	ax       As Integer		' horizontal acceleration.
	r        As Integer		' horizontal friction.
	frame    As Integer		' animation frame #.
	ps       As Integer		' animation subframe counter.
	dontFall As Integer		' flag set if jumping.
	flag     As Integer		' general purpose.
	prevX    As Integer		' last x coordinate before jumping.
	prevY    As Integer		' last y coordinate before jumping.
	facing   As Integer		' left = 1, right = 0
End Type

"Real Numbers" in Integer Variables

We want this smooth. We want that the objects in the game move along nice curves. That implies some "real" numbers, i.e. numbers will decimals, so a "pixel" is not the smaller unit in our "world".

Some will say that I could do this with floating point numbers, that the floating point unit works and it is fast, that integer numbers are not needed anymore for speed, and some other things, but this is my way. I grew up in the times when floating point math was slow and was completely unsuited if you wanted a fast paced game, so I learned to use integers in an intelligent way.

The "trick" is as follow: imaginary divide each pixel in 100 "sub-pixels", and place your coordinates using those units. That way, if x = 6700 that means that the player is located at pixel 67 horizontal. Multiplying by 100 will translate from pixels to "units", and dividing by the same figure will do the opposite operation.

Now you might be thinking that, having to divide and multiply constantly, it would be better to use powers of two (such as 128 or 256) and then shifts to gain even more speed, and you are right. I'm using 100 here just for readability. Just by looking at the figure you know which pixel position it refers to, which is more suited for learning. Once you are more familiar with how everything works, I suggest you to use powers of two instead of 100, shifts instead of division and multiplication and ANDs instead of modules, just remember the three most well-known optimizations:

a * 2^n = a shl n (example: a * 256 = a shl 8 )
a / 2^n = a shr n (example: a / 128 = a shr 7)
a mod 2^n = a and (2^n-1)) (example: a mod 8 = a and 7)

PSC's

Pseudo-Stupid Characters, that's why we call our non playing characters, i.e. the baddies or whatever you want moving in your map. First of all, we have to make some desing decisions:

Placement and disappearance of PSC's: We have to decide a couple of things, as we have several options. For example, we could place ALL the PSC's along the map and have them fixed and always moving, or we could only move them when the are on screen, or we could make them appear in the edge of the screen when we reach somewhere and destroy them as soon as they exit the screen... Everything depends on the type of game we want. For fast platform arcades it is cool if you "create" the PSC's on the fly, i.e. when you reach to a point it just is created and starts moving. When the PSC is too far from the camera, it is destroyed. This is, for example, how Mario or Sonic work. On the other way, we could just create all of them at the beginning. That allows to find a dead PSC we just killed when we come back, instead of getting a brand new one.
Whether a PSC is a bad guy or not, i.e. whether it kills when touched you or not. Also to decide is if it substracts you a life when it touches you or it eats your energy. In this case, we should have to add an "energy" field to the PlayerType structure, and information on how much energy it takes each collision.
Whether we want certain PSCs to shoot.
The kind of movement and/or AI we want to give each "kind" of PSC

All of this, and how to implement it, will be discussed in the PSCs section, which will be the longer, most complex, final part of this tutorial.

Enough

We've introducted this more than enough. Next month we'll build the parallax engine.

Check out Na_th_an's programming site, Los Monos del Obús. Oh yeah, and his awesome QB platformer Jill The Goddess.

COMMERCIAL AND PROFESSIONAL APPLICATION DEVELOPMENT
Part Three - The Conceptualization Process

Written by Stéphane Richard (Mystikshadows)

INTRODUCTION:

And here we are, the 3rd part of this series. What exactly can you expect in this section? Well let's start by stating what you would typically have before arriving to this section. In theory, you would have your analysis documents (the 3 of them) completed, you would have gotten the solution discussed and approved by management and everything is ready to go to the next step of the development cycle. What is that next step? It's called Conceptualization phase, and entails the beginning of the creation of the proposed solution as it is defined in the detailed analysis and the solution proposal document. Since any flow of information between process steps and between departments in the company (if need be) have been defined in the detailed analysis, you should be ready to go on and start to create the solution. In this 3rd part of the series, we'll cover all you need to know about the conceptualization phase, what it is, what tools are available to you during this phase, and some good practice to use throughout the process.

By the end of this 3rd part, you will be well equipped with the knowledge you need to conceptualize an idea into a workable solution ready for the development phase (which we'll cover in the next part of this series). So indeed, there's alot of ground to cover here. Grab your favorite drink and let's get started shall we?

WHAT IS THE CONCEPTUALIZATION PHASE:

In the software engineering field, conceptualization is taking everything in the analysis and building a solution from all the information gathered in the analysis phase. Of course, as I mentionned in the previous section, there are many ways to arrive at that, and each of those ways involve a different point of view on the creation of the solution. I'm not going to detail each method again here, you can review them here. if you recall, I mentionned that we would be using UML (Unified Modelling Language) for our project, and that is exactly what we will be doing here.

Is there a preferred order of things that can work better than others? Many software engineers might argue on this. Me, I tend to use somewhat of a top to bottom approach in that I'll start with the bigger, more complex objects (which are usually objects that are made of other objects) and work my way down to each object that the bigger objects are made of. The reason I work in this order is it gives me a bigger picture so to speak and i can work on the relationships between the objects as I break them down. Since we'll be using UML as our tool, actually, we'll be using a text version of UML which means that I'll be describing the objects as text as well as the relationships between the objects. This is a quicker method than going into some application and creating UML diagrams. And it can be done in notepad or your favorite text editor. Let's start by covering what UML is and what it allows to do to familiarize ourselves with it.

UNIFIED MODELING LANGUAGE BASICS:

U.M.L. is a language that used to describe a problem based on the entities involved, howw to describe these entities (properties) and what those entities can do (methods). UML also alows to describe the relationship between each entity. It doesn't stop there however, UML is also used to describe Organization Diagrams, Use Case Scenario diagrams, Activity and State diagrams, and Static and Dynamic Model (class) diagrams, Sequence Diagrams (to explain certain ordered steps), Collaboration diagrams (where more than one process need to work together to get a given job done) as well as a whole bunch of other types of diagrams that are useful when modeling a solution from start to finish.

For some reference you can take a look at Allen Holub's UML Quick Reference which details all the types of diagrams that are available in UML as well as examples on what those diagrams can look like. Also you can take a look at the UML 2.0 Superstructure Final Adopted specification. With these documents at hand, you'll be equipped to tackle any conceptualization model you would be likely to encounter.

I need to add a distinction here. In many cases, people tend to confuse the concept of composition versus the concept of aggregation. So I will explain these two right here to a bit of clarity. Here they are:

Aggregation:
An Aggregation represents a whole entity that comprises other parts. For example: a committee is an aggregate of it's members. However, in the case of an aggregation a commitee does not contain it's members per se.

Composition:
A composition, unlike the aggregation, has everything to do with containement. For example, a horse is a mammal, and will never have a reason to be nothing else but a mammal, therefore, a mammal contains a horse.

With all this in mind, you can see that UML can be a very powerful tool to add to your arsenal of software engineering tools for more than one reason. For the sake of this example, we'll be using what I called a text version of UML as in there will be no diagrams. The description of objects will be nade in a textual, almost pseudo code like even, because when you look at an object class model diagram, that's exactly what you're seeing for an object is all it's properties and methods listed and described. If the need for a sequence or a collaboration diagram is needed in our description I will use lists or paragraph describing the sequence and/or collaboration. This way you should be able to see clearly what should be going on in an object. Also as mentionned, I will start with the bigger objects and clearly state what the object is composed of. the components of the objects will be detailed later in the scripted UML model.

FINANCECAD SCRIPTUAL OBJECT MODEL:

To start this model, I will begin at the highest possible level of FinanceCAD, the Application itself. Indeed the FinanceCAD Application can definitaly be thought of as an object, a very complex object that comprises everything else in the project.

ENTITY FinanceCAD

   PROPERTIES:
       ApplicatioNPath  Text
       VersionMajor     Numeric
       VersionMinor     Numeric
       VersionRevision  Numeric
       VersionRelease   Character
       VersionStamp     Text

   METHODS:
       CreateNewDesign  <- DesignName Text
       OpenDesign       <- FileName Text
       SaveDesign       <- FileName Text
       PrintDesign      <- PrinterNumber Numeric

   COMPONENTS:
       OBJECT Canvas             <- The main Drawing Canvas
       OBJECT DatabaseEngine     <- File and database functionality
       OBJECT PrintingEngine     <- Printing functionality for the design
       OBJECT ReportEngine       <- Printing Functionality for the reports
       OBJECT NetworkEngine      <- Detection and access to the network folders
       OBJECT ImportExportEngine <- Import and Export for the design and the reports

   RELATIONSHIPS:
       No relationship at this level of refinement.

END ENTITY

So far it's not too long is it? There's a median to reach when you are describing a problem using this approach. For the sake of our example here, there's no need to go into any more details, at the application level, than to list what the general components of the application would typically be. As you can see from this first description, things can become obvious quite quickly using this description method. You described the Application just as you would any other type of object. All Objects have qualities and properties that describe them, they also have actions that they can perform. Just by saying what the object looks like, and what it can do, you end up with a pretty complete description of the object itself. Take a look at the Canvas object defined below, you'll see what I mean when I say a complete picture.

OBJECT Canvas

   PROPERTIES:
       FileName         Text
       UnitOfMeasure    Numeric
       Scale            Numeric
       NumberOfShapes   Numeric
       Layers           List

   METHODS:
       Create           <- The constructor, called when object is initialized
       Destroy          <- The destructor, called when object is destroyed
       SetUnitOfMeasure <- NewUnitOfMeasure Numeric
       SetScale         <- NewScale Numeric
       ClearCanvas
       RefreshCanvas
       AddCircle        <- Layer Numeric, Radius Numeric
       AddEllipse       <- Layer Numeric, Ratio Numeric
       AddArc           <- Layer Numeric, Ratio Numeric, Length Numeric
       AddSquare        <- Layer Numeric, Length Numeric
       AddRectangle     <- Layer Numeric, Height Numeric, Width Numeric
       AddTriangle      <- Layer Numeric, TriangleType Numeric, Lengths() Numeric
       AddHexagon       <- Layer Numeric, SideLength Numeric
       AddOctogon       <- Layer Numeric, SideLength Numeric
       AddLine          <- Layer Numeric, X1, Y1 Numeric, X2, Y2 Numeric

   RELATIONSHIPS:
       One To Many      -> Circle Object
       One To Many      -> Ellipse Object
       One To Many      -> Arc Object
       One To Many      -> Square Object
       One To Many      -> Rectangle Object
       One To Many      -> Triangle Object
       One To Many      -> Hexagon Object
       One To Many      -> Octogon Object
       One To Many      -> Line Object

   DESCRIPTION:
       The Canvas object is where the drawing of the design actually occurs.  It
       is composed of a drawing area and a command processor (to get and process
       all the different commands that would typically be entered.  The One To
       Many relationships to the different Shape Objects are because Shapes are
       added to the canvas rather than just drawn. This way, each shape can be
       treated as an independant entity and moved independant of the other shapes
       on the given design.

END OBJECT

The first thing to notice here is how I categorized each descriptive element. this method is the one I prefer to describe a physical object in an application hierarchy. I'm not going to define the Circle, Ellipse and the other basic objects for this example. Just remember that when describing a different scenario (typically when you are modelling a manual process) it will be a good idea to define each little element that make up a given object. In this case the Circle object and the other shapes would be defined in the same fashion as the canvas objects with the properties section, the methods, relationships and so on.

We'll just go down the list of objects in the order they have been defined in our application entity. As such, here's the definition of the DatabaseEngine object:

OBJECT DatabaseEngine

   PROPERTIES:
       DatabasePath     Text
       ConnectionString Text
       ConnectionMade   Boolean
       TableCount       Numeric
       TableList        List  Table Objects

   METHODS:
       Create           <- The constructor, called when object is initialized
       Destroy          <- The destructor, called when object is destroyed
       ConnectToDB      <- ConnectionString Text, DBPath Text
       ValidatePath     <- PathToValidate Text
       OpenTable        <- TableName Text
       ExecuteQuery     <- QueryToExecute Text
       InsertRecord     <- RecordData Text
       UpdateRecord     <- RecordData Text
       DeleteRecord     <- RecordNumber Numeric
       FindRecord       <- Criteria Text

   RELATIONSHIPS:
       One To One       -> NetworkEngine Object

   DESCRIPTION:
       The DatabaseEngine as defined here is not a Database Management System
       but rather a wrapper that connects to the existing database engines via
       the ODBC database connectivity library.  Each method will therefore
       portray a function calling to the inner ODBC functions in the actual
       coding phase. The relationship to the Network Engine is for validating
       the actual path to the global database and assure proper connection
       between the the Database Engine and the physical location of the
       database itself as well as validating the existence of the network
       printers and plotters to print the designs and the reports.

END OBJECT

And that was the DatabaseEngine object definitions. As you go along refining the object model when issues get solved and questions get answered, you may want to add to this model. For example, maybe you'll find you need more properties in the list of properties depending on what the users know that they need to get access to the database. Perhaps the ability to specify a username and a password to the ConnectDB method rather than the way it's designed right now. You need to remember that typically you are at the start of the conceptualization phase and that you may as the modelling moves along, move properties and methods around to other objects perhaps for whichever reason. Just remember that you need to have an open mind at this stage of conceptualization. Things can and will change in your model and knowing that in advance can influence the initial design to be as open and flexible as it needs to be to allow for these changes. As a quick note, you can see I named the constructor and the destructor the same name as the canvas object. It's good practice to name functions that perform the same things by the same name not just in the conceptualization phase but throughout the whole development cycle all the way to the source code as well. This way you know that Create will always create and initialize the object no matter what that object is.

Likewise, the PrintingEngine Object is defined as any other objects it has properties and methods that will be used by the main application object at will to get things in output format. A typical definition for a printer object could be as follows:

OBJECT PrintingEngine

   PROPERTIES:
       PlottingJobs      List
       PlotterList       List
       JobCount          Numeric
       HasJobsToDo       Boolean

   METHODS:
       Create            <- The constructor, called when object is initialized
       Destroy           <- The destructor, called when object is destroyed
       DetectPlotter     <- PlotterToDetect Text
       InitializePlotter <- PlotterToInitialize Text
       AddToJobs         <- JobNumber Numeric, FileName text
       PrintFirstInList  <- No Parameters, will print the first job in list

   RELATIONSHIPS:
       One To One        -> NetworkEngine Object
       One To Many       -> ReportEngine Object

   DESCRIPTION:
       The PrintingEngine as defined here is a central object where all
       printing jobs are passed.  This object will determine the type of
       document that is being requested for printing, determine where it
       should be printed (Physical location of the plotter) and send the
       job to there to be printed.  It does nothing to the actual
       design file itself other than send it to be printed.  The One to
       One relationship to the NetworkEngine object is to detect the
       presence of the plotter that has been configured by the design.
       The One to Many relationship to the ReportingEngine Object is
       because when the user prints a design he or she could want to
       print more than one report for the cost of the design itself.

END OBJECT

There you have it, the PrintingEngine Ojbect as you can see is the object that manages and prints The Design file itself. In the description part is where you defined the exact relationship between the object as I've done here. it will help the coding phase alot to know why a relationship is defined. Notice how every object is defined using the same structure no matter what it's role is. That's the beauty of this method. Consistency in structure will help you, and everyone that needs to see the model, quickly learn how to read the model and where to locate vital information they will need in their part of the project.

To continue with our modeling, as per our list of components in the Application definition the next object on our list is the ReportEngine Object. So then, let's define that one right now:

OBJECT ReportEngine

   PROPERTIES:
       PrinterJobs       List
       PrinterList       List
       JobCount          Numeric
       HasJobsToDo       Boolean

   METHODS:
       Create            <- The constructor, called when object is initialized
       Destroy           <- The destructor, called when object is destroyed
       DetectPrinter     <- PrinterToDetect Text
       InitializePrinter <- PrinterToInitialize Text
       CreateSummaryCost <- DesignFile Text
       CreateDetailCost  <- DesignFile Text
       AddSummaryJob     <- JobNumber Numeric, FileName text
       AddDetailJob      <- JobNumber Numeric, FileName text
       PrintFirstInList  <- No Parameters, will print the first job in list


   RELATIONSHIPS:
       One To One        -> NetworkEngine Object
       Many To One       -> PrintingEngine Object

   DESCRIPTION:
       The ReportObject takes care of all the paperwork related to a given design
       file.  the user will have 2 choices when requesting a report to be printed
       with a design.  He or she can have a sumarry report (usually used inhouse
       for quick evaluation of costs) and a detail report (usually used both
       inhouse and sent to the client for aproval purposes.  The two reports are
       added to the same list of print jobs as they will typically be sent to the
       same printer.  The One to One relationship to the NetworkEngine Object is
       to validate the existence of the physical printer on the network.  The
       Many to One relationship to the PrintingEngine is because the reports that
       are offered here are only available when printing a design (an optional
       checkbox may be added to select to print just the design, the design and
       the report, or just the report, but they will all originate from the same
       print dialog).

END OBJECT

The good part of this type of definition is let's say the users, even at this stage of the conceptualization process, decide they want another type of report, all you have to do is add an Add________Job method (these will be defined at the coding phase). The model can stay as abstract as needed to isolate itself from the actual coding of the application this way. By tracing this line between the conceptualizaton and the coding phase, it's easier to set a limit to when the conceptualization phase will end and when the coding phase will begin. Note that so far there are no screens or any visual aspects defined at this stage either. You'll see why in the next section, the coding phase of the development cycle. But let's just say here that the coding phase is and should be split into two sub-phases, The design phase and the programming phase.

Moving right along in our model, the next object to attack is the NetworkEngine Object. Before we begin the model, just keep in mind one thing. Unlike the rest of the objects here, the NetworkEngine object is an independant object in that it doesn't need the other object to execute itself, however, there are relationships because the other objects of the application will give the NetworkEngine object it's purpose of existence. So let's define this object and we'll see what I am talking about:

OBJECT NetworkEngine

   PROPERTIES:
       DriveCount        Numeric
       ListOfDrives      List
       PrinterCount      Numeric
       ListOfPrinters    List
       PlotterCount      Numeric
       ListofPlotters    List
       IsNetworkPresent  Boolean

   METHODS:
       Create            <- The constructor, called when object is initialized
       Destroy           <- The destructor, called when object is destroyed
       GetListOfDrives   <- No Parameters, gets list of network drives
       SetDriveCount     <- Count Numeric
       ValidateDrive     <- DriveIndex Numeric
       GetListOfPrinters <- No Parameters, gets list of available printers
       SetPrinterCount   <- Count Numeric
       ValidatePrinter   <- PrinterIndex Numeric
       GetListOfPlotters <- No Parameters, gets list of available plotters
       SetPlotterCount   <- Count Numeric
       ValidatePlotter   <- PrinterIndex Numeric

   RELATIONSHIPS:
       Many To One       -> Canvas Object
       Many To One       -> DatabaseEngine Object
       Many To One       -> PrintingEngine Object
       Many To One       -> ReportEngine Object

   DESCRIPTION:
       The NetworkEngine Object is an object that performs all necessary validation
       against the network in order to get all the valid drives, printers and the
       plotters that are available on the network. The list of drives will contain
       the physical Drive Letter, the logical Drive number, and the network path
       to the physical hard disk.  The list of printers will contain printer
       relevant information such as printer path, shared name, and the likes.  The
       same goes for the list of plotters.  The printers and plotters will be
       initially determined by the printer drivers installed on the user's machine
       then validated against the printer and plotter list on the network.
       All of the many to one relationships are established because the Canvas,
       DatabaseEngine, PrintingEngine and ReportEngine will use the NetworkEngine
       to determine the existence and validity of the drives, databases, printers
       and plotters that were configured at the application level (hence on the
       user's installation of the FinanceCAD Application).

END OBJECT

In most cases, a One to Many relationship determines that the modeled object has one or more of the related object. This is know as a "has a" relation. When you encounter a Many to One relationship usually indicates that the modeled object uses the related object. This is called a Uses relationship. This can mean that it uses the related object or is used by the related object. To know which of the two is entailed, you'll need to look at the related object's relationships section and the description.

One more object to worry about, it is the ImportExportEngine object. If you remember in the previous section, there was mention that the design, and the attached reports have the ability to be exported into more well known file formats for compatibity purposes. In this object I'll introduce sequences (or order in which steps are to be performed) and how to define them in the definition of the given object. So then, Here is the definition of the ImportExportEngine object:

OBJECT ImportExportEngine

   PROPERTIES:
       ImportFormats     List
       ExportFormats     List
       FileName          Text
       FileType          Numeric
       ImportFormat      Numeric    [Index to the Import File Format]
       ImportCompleted   Boolean
       ExportFormat      Numeric    [Index to the Export File Format]
       ExportCompleted   Boolean

   METHODS:
       Create            <- The constructor, called when object is initialized
       Destroy           <- The destructor, called when object is destroyed
       ImportFromDXF     <- DXFFileName Text     [Autocad Data eXchange Format]
       ImportFromWMF     <- WMFFileName Text     [Windows Meta File Format]
       ImportFromTHREEDS <- THREEDSFileName Text [3D Studio file format]
       ExportToDXF       <- DXFFileName Text     [Autocad Data eXchange Format]
       ExportToWMF       <- WMFFileName Text     [Windows Meta File Format]
       ExportToTHREEDS   <- THREEDSFileName Text [3D Studio File format]
       ExportToDOC       <- DOCFileName Text     [Microsoft Word Format]
       ExportToWPD       <- WPDFileName Text     [Word Perfect File Format]
       ExportToPDF       <- PDFFileName Text     [Adobe Portable Document File]
       ExportToRTF       <- RTFFileName Text     [Microsoft Rich text Format]
       ExportToHTML      <- HTMLFileName Text    [HTML 4.01 Compliant format]
       ExportToTXT       <- TXTFileName Text     [Standard ANSI Text File]
       ExportToCSD       <- CSDFileName Text     [Comma Seperated File Format]
       ExportToXLS       <- XLSFileName Text     [Microsoft Excel Spreadsheet]
       ExportToWKS       <- WKSFileName Text     [Lotus File Format]
       ExportToDBF       <- DBFCFileName Text    [X-Base compatible format]

   SEQUENCES:
       Importing from a format
       1. Select the file to be imported
       2. Determine format based on file extension
       3. Perform the import

       Exporting to a format
       1. Select a file from the list of files
       2. Select the desired output format
       3. Perform The export

   RELATIONSHIPS:
       Many To One       -> Canvas Object
       One To One        -> NetworkEngine Object

   DESCRIPTION:
       The ImportExportEngine object is created at the start of the application
       and available live from the main application object.  when a Design is
       created, or opened, the ability to export the design itself or the reports
       are also made available for direct access to it's functionality.  This way
       the user can export the design and/or the reports anytime he or she wishes
       to do so. The many to One relationship with the Canvas object is defined
       because Any of the open Canvas Objects (hence any Opened design files) can
       be exported.  The One to One relationship with the NetworkEngine Object is
       present for drive and folder validation purposes only.

END OBJECT

You can see that I used file extension as a mean to differentiate the different file formats I plan on being compatible to for the design file and for the reports as well. You can also see that I don't import anything for the report files as only exporting of our reports are necessary. Here to the constructor and destructor of the object are named the same as all other objects for familiarity and the beginning of a certain naming convention that can be followed all the way through the coding phase. As you can see, sequences are nothing more than an ordered enumeration of what needs to happen in what order, simple as that really. And that goes for any model that may need any type of ordered list of objects or list of actions to take.

And there we have it, the modeling is completed. we've defined our application object and it's 6 components. In the coming section we'll see what we can extract, as far as notions are concerned, from the model as well as some special considerations and notes that need to be mentionned for all your modeling projects.

CONCEPTUALIZATION CONSIDERATIONS:

As I mentionned before, this model is rudimentary and at the surface level of the objects it models. The goal here is to teach you what modelling is and I believe this top level of refinement is more than adequate to show you how it's done. In a typical scenario however, you would be modeling everything from the top level down to the bottom levels of an object hierarchy. To know how low a level you need to go to, you just need to know where your entities end and when you can only talk of properties and methods of your entities. When you can no longer define an entity as having sub entities (objects) then the hierarchy is complete and so is the levels of refinement of your model. It's the best trick I can give you.

The order where I defined the methods is important in this model. the only Object I have defined sequences for is ImportExportEngine object. In the case of the other objects, if a certain order of things is needed, they can be define simply by the order in which the methods are defined in each object. The specific order of things are usually defined either in the user requirements document (when the order are ordered set of steps or commands to get towards the accomplishment of the desired function). or the detailed analysis document (when the order of things are steps to execute a given process).

This is why it's important to be prepared before entering the conceptualization phase. As you can see here, when you have all the documents you need, before you enter the conceptualization phase of the development cycle, you have all the information and tools you need to get through the conceptualization phase as straightforwardly and as smoothly as it can possibly be. And since this phase is a big part of the development cycle, I would urge you to take the time to be as prepared as you can be before you start the conceptualization phase. You'll thank yourself later.

A WORD OF CONCLUSION:

That was a big load to digest wasn't it? Well, when you have the right notions, it is a big job to conceptualize, but it can be quite rewarding as well, when you are well prepared, you'll find out that this phase will be invalluable for the rest of the development cycle. I can't stress enough that the key to this phase, and absolutely all phases of the development cycle (as defined in the 1st part of this series) is to be prepared. If you take the extra time to ask the right questions, you'll get the right answers to work with. This is true for all phases. There are types of projects that for some reason are harder to gather a complete range of information than others. This is usually a sign that the application will need to consider adaptability in the process. For example, many reporting systems may not know, in advance the whole list of reports it will need to create. In this case, being prepared means you have a list of report as are currently known. Adapability means the reporting engine is designed to accept new reports as if they were always part of the list of reports and therefore can be as integrated to the system as the known reports would be. There are other situation where it's difficult at best to acquire a complete list of specifications or list of reports, or list of things that will need to be implemented as well. But again asking the right questions in this case will tell you, atleast, that what you have is incomplete and should be made to grow. This is also called programming for the future.

And that's it for this part of the series. I hope you enjoyed it, and especially, I hope you learned what I tried to teach in this document. Remember, as always that I am there to answer questions as well as for comments and suggestions so email me with any concerns or discrepencies in what you've learned so that we can clear things up together. AS such, a note must be made that the contents might change if I get enough requests to make certain parts of this document clearer than they already are. In the next section we'll attack the coding phase in all it's glory. We'll see why being prepared is important at that phase too, just like all other phase of the development cycle, and we'll see all the special consideration we'll need in that phase. Happy reading and see you then.

MystikShadows
Stéphane Richard
srichard@adaworld.com

Check out Issue #9 for parts 1 and 2, or download a copy of this tutorial.

COMMERCIAL AND PROFESSIONAL APPLICATION DEVELOPMENT
Part Four - From Conceptualization To Application

Written by Stéphane Richard (Mystikshadows)

INTRODUCTION:

Welcome to this Fourth part of this series. We've covered, I believe, alot of ground so far in this series, and this fourth part will be no exception. In this part we will be covering everything there is to know about the Development phase, or the Coding phase per se. We will be seeing what is available to you at this stage of the development cycle just as we have in the other phases. You'll also see here why the previous phases are important even in the coding phase. You need to understand that all documents, from the analysis documents to the modeling of the application play their role in this phase. You'll see how, and where, in this document. The coding phase is where you take all the knowledge, that you built from the analysis and conceptualization phase, and materialize them into an application. To do so, the right way, most big application projects will need a bit of preparation and documentation about different parts of the application to build.

With this in mind, let's begin this 4th part of the series by seeing what makes up an application and later we'll defined what is needed for each of them as far as documents (however detailed they may or may not need to be). Since our first target operating system is Windows™, the rest of this document will taking the target operating system into consideration throughout its contents.

THE MANY VISUAL PARTS OF AN APPLICATION:

Aside the objects defined in the UML Scriptual Model in the previous part of this series, there are also other types of components to consider when you are building an application. They each play their role in to proper operations of the application and well should be considered as independant of the main engines of the application. Here is a list of these parts along with their descriptions and considerations (if any):

The Application Itself:
In a windows™ application, there are 2 distinct standard when developing applications. The first that was created was S.D.I. (Single Document Interface) which tends to present every part of an application in it's independant window that offers no relation to the main Application window whatsoever. The other standard is called M.D.I. (Multiple Document Interface) and that one tends to offer the ability for other windows (usually the windows that pertain to the actual working document or database) as a child window to the main Application Window. This offers a visual indicator that a given form belongs to a given application and this is mainly why it became popular quite quickly. In our case, we will be using the M.D.I. standard means of presenting the application for all the popular reasons.

The Menu System:
The reason I mention The menu system this early in the list is because the menu system is usually and typically the part where all other parts of the application are accessed from. In the Windows™ operating system this is usually represented by a menu bar (at the top of a window) from which menu options are pull downwards when a menu option in the bar is clicked. Because of that action to virtually pull down the menu, this type of menu system was duely named a pulldown menu system. It was adopted way back in 1984 with C.U.A. (Common User Access) sub standard of the S.A.A. (Standard Application Architecture) standard as defined by I.B.M. The Menu bar typically have one word options only so when creating it you will need to make sure the top level of your menu are a list of one word options. The sub menues can have 2 or more words because they can be more detailed hence clearer this way. Again the C.U.A. standard defines certain common names for menu options that perform common tasks in all windows application you can look at other applications to see where these standard menues are and how they are named. Your menu should reflect that standard as much as possible to be easily learned by your users.

The Main Application Form:
Let's use examples here. For Microsoft Word™ the main application window is the Document, for Excel, it's the spreadsheet file. In the case of FinanceCAD, the main application window will be the window where the user can created their design on. It's the window from which the main supported file, document, format, datatabe are managed, editor or controled from. For the pulldown menu most function in the File Menu (usually the first in the list) create or close a main application window and most functions in the Edit, Insert and Format menues would typically affect the current main application window. The main application window will have a main drawing area (which will cover most of the window) along with 3 smaller windows offering alternate views on the main window (top, left and right views on the main design).

The Accessory Forms:
Indeed there's usually more than one of those involved. These forms are forms that affect what is currently selected in the main application window. For example, in Microsoft Word™ if you select text and go to the Format menu and select the fonts, a dialog appears letting you select which font you want, it's color, if it's bold or italic etc etc. When you close the form, whatever you selected on the form is then applied to the main document window's currently selected contents. This is the basic role of an Accessory Window. It's easy to see where we might need more than one. But they are used to help make things clearer and can be used at will. FinanceCAD will have at least one for each type of shape that can be inserted into a design as well as a special form to allow to preview and select the coumpound objects that can be built with the application to be used in any or all designs.

The Independant Forms:
These forms may or may not be related to the main application window. They can be forms that perform a task with the currently opened file such as the print document, or forms that have a specific purpose that is unrelated from the currently opened file (the printer options dialog is a good example of this). All you need to know is if the form needs the current main application window in order to get their job done, then they should be considered as accessory forms. In the case of FinanceCAD there will be many of these independant forms, for some example, the file open and save dialogs, the setting of the Design's scale (which doesn't need the main application window per see except that it affects it once a scale is selected). Usually File Open and File Save dialogs are considered system forms (see below) but in our case these dialogs will be custom made because of the added functionality such as design preview and others.

The System Forms:
These forms don't usually need any design. They are supplied either by the Windows API or the runtime library of the language being used. They provide standard OS functionality such as, but not limited to, folder selection, file open and save, standard font selection and standard color selection dialogs. No matter what the operating system running the application is, it is recommended to use the standard dialogs whenever there's no need for added functionality on the part of the application. For FinanceCAD, the file open and file save dialogs as well as the printer dialog will be created since we need more functionality that is provided by the standard dialogs. In many cases however there is no need to do this and you can use the system forms without a problem.

The Option Forms:
These forms have a very special purpose in a typical application. They serve to set the options that are to be made available globally throughout the whole application. What you will typically see is a global option form and a Document level set of options. They usually have tab controls to seperate the functional groups of options and one saves in the application's configuration file, the other saves it at in the document file itself. FinanceCAD will be no exception and will have application level options as well as design level options available to the user. For this we will need Option Forms as they are best used for this specific purpose.

The User Feedback Forms:
This type of form was created to give a consistent feedback to the user. Feedback is an important aspect of application development no matter what the operating system you are using. Today, no user likes to be left in the dark and wonder what just happened when he clicked on something or pressed some keyboard combination. If the button was there to let the user save a design for example, you should let them know that the saving of the design has been completed successfully and if there was an error, the user should be made aware so he doesn't assume that his design was saved when it really wasn't. Feedback form can play that role if used intelligently. They are typically used to report progress, errors if any, or even to allow to confirm that the user really wants to perform the selected action. Letting the user know what just happened and giving the user a chance to cancel an action is taken for granted these days simply because they are a given. Any application today should have them so they are expected no matter what the applicaiton is.

Those are pretty much all the forms you might ever need. Some very specific applications may find a different type of form but usually, simple common sense is all you need to figure those out as they are presented to you. I wanted to make a whole section on forms and dialogs because when you are creating an application, user interactivity is always an important aspect to your application, it's the part of the application that your users can make themselves an opinion on your work so when you design your forms, it's important to take the time to design them properly, align your controls, give your whole application a professional and consistent look and feel and users will like to use your application. Remember that you never get a 2nd chance to make a good first impression so the impact of your forms on your users should be top priority on your list of considerations especially if the application is to be sold commercially (in which case your forms also need to be universally acceptable to the common user).

And now that we also covered the visual aspect of an application, we can move on to the actual programming of the forms and the rest of the application. So let's talk a little bit about what development is exactly and see how we can go about developing the application.

WHAT IS THE PROGRAMMING PHASE:

The best way to describe the programming or coding phase is to simply say that this phase takes the documents and models as they were defined in the analysis and the conceptualization phase and creates an application that confirms to these documents and models. Sounds simple doesn't it? In a way I would say that it is that simple, long because applications this size still need a minimal time to code for, but simple nonetheless. Because of the importance of the visual aspect of an application as describe above, I would highly recommend breaking the coding phase into two independant sections. These sections are:

The Visual Design Phase:
Yes some may argue that the design phase could have happened in the conceptualization. Maybe, in some cases, it can. However, when you think of what you have at the conceptualization phase, all you have, typically, is required information, work to be done and desired output. You just don't have a complete baggage of information to design your forms. You could maybe create a rudimentary form to show your users, but chances are you'd have to change the design of your forms at least a few times before they are actually approve. Not to mention that during the conceptualizaton phase even the required input might change dramatically. So I like to have a whole phase dedicated to design forms like this. this way, every knows the phase is coming and everyone can plan to have some validating and aproving to do on the design. It also allows to close the design phase with atleast a minimal degree of certainty so that when these forms are to be coded, there are less chances that the forms would change as this phase is created to take the time to approve the forms.

The Programming Phase:
At the same time as the design phase, if you have enough programmers to do so, these programmers can start working on the non visual aspects of the application. There is always a non visual aspect and the more time you have to work on that part, the better. This is the place to start creating some test cases for the code to come whether it is a form or some calculation engine or whatever other parts of the application that will ultimately need to be thouroughly tested. With the model of the application that you created at the conceptualization phase, along with the user requirements documents and the detailed analysis, you should have everything you need to accurately produce the solution to the problem at hand, in our case, FinanceCAD. The time to attribute to the development phase depends on how many forms you need to create, how many engines (or non visual elements of the applications) and of course the number of programmers that you have at your disposal.

I should note that sometimes the Visual Design Phase is spread out across the programming process in that each form is first designed, shown to the users to be approved, then the inner workngs of the form are coded and the form is then put to the test. I say this because not every company works the same way, but even if done on a form by form basis, the design phase is still very present and very important, it would be futile to create a form, code everything that goes under it, then show it to the user to see if they like it because you have 1/2 chances that they won't like it and you'll then have to start over from scratch. In the corporate world that's a very big lost of time for you, your team and the users which also means it's a waste of money. The more of these little waste of times you can avoid, the better it is for the life of the project, that goes without saying of course. Once again good planning from the start, all the way to the coding phase helps prevent alot of these situations just because you took the time to think about things for a little bit.

Of course, to begin the coding phase, it makes sense to know what programming language you'll be using since, obviously, it will be your main tool from now on in the development cycle. The following section will help you make the choice of language by highlighting some language features that you might want to consider for the project at hand. I will be covering the languages at the language level itself, not the brand of compiler. I will show you the popular compilers for each language however but just as a reference, not as a criteria for selecting the language itself.

WHICH PROGRAMMING LANGUAGES SHOULD YOU USE:

That is always a big question, it's not always as simple as saying "well everyone's using this language so I'll just go ahead and use it", atleast, it shouldn't be. The choice of language is just as important as the choice of tools you'll have to make throughout the rest of the development cycle and depending on the project, that can represent a big portion of the project's life. So then, what makes a language better suited for a given task? Well, if you really know what the task is, it's easier to come to a decision if you also know your languages. Of course, this is an ongoing debate, C and C++ programmers will argue that only C or C++ is the language to use, Ada developers will say otherwise, Pascal programmers will have their version of the story, VisualBasic users, well, you get the idea. You really have to sit down and write some list of consideration to choose the language. You see, all language manufacturers boast their own respective language as beeing an all purpose language capable of taking of all possible types of projects and project sizes. Now you need to take a step back, and think about what you want for your application and see what languages meet the criteria. Let's review what feature of FinanceCAD we have and let's see what we can determine from them:

FinanceCAD is a Graphical Application:
That is actually very important to mention right upfront. Let's face it, if you write a graphic routine, put it in a loop, execute it 1,000,000 times, you'll quickly notice that some languages handle graphics in a lighter and faster way when compared to others. Sometimes that difference is almost negligeable but in other circumstances, because in our case, FinanceCAD, being a graphical application, should be the fastest it can be as far as graphics are concerned. When I say graphical I don't mean that the application runs on a graphical user interface, I mean it creates graphical design files. All language can create Windows Application today, that doesn't make them all suitable for an application that manages and processes vector graphic files. The same goes for the Linux KDE, Gnome, and other Graphical User Interfaces you may encounter on any platform you may encounter as well. If the application has competition like the case of FinanceCAD, then performance becomes the most important issue quite quickly. these are the types of questions you need to ask yourself when choosing your language.

FinanceCAD will be multiplatform:
Pretty much all language have some implementation in most existing platforms, that's not a secret, however, not all language were designed to be multiplatform. Some languages will require quite alot of work to be ported to it's equivalent language in another platform, other languages just seem to flow between platforms like they were made for all of them. If you plan on porting your application to more than one platform, the choice language will determine the amount of work you'll need to actually port the application and that can be a very important factor if time, or costs, are important factors to the project. If we were to assume for example that FinanceCAD would only be developed for the Windows™ platform this feature wouldn't even be in the list but since it is to be multiplatform we have to take it into consideration when selecting the language. You'll see later that there are libraries available that can save you alot of time for GUI design for a multiplatform project and they too should be considered, even used whenever possible to minimize the porting time involved.

FinanceCAD will need databases:
As you remember, there's a considerable amount of database related functionality to be done. We need to stop and ask two important questions. First we need to ask ourselves what database should be used for the project as in what specific database features we are looking for. Here we need basically some querying capability so that should tell us that and SQL compliant database is in order. Second, we need to ask ourselves how easy it is for the language we'll be using to access these databases. Indeed, languages like Microsoft VisualBasic™ and Borland Delphi are known to be languages that can very easily connect to most databases available out there. Others may allow to connect to a database but with very specific set of low level functions that tend to become more problems than is usually worth. I say usually because in some cases, the rest of of the features of the application can superseed any problems or complications that can occur from using low level database API such as ODBC32 and others. It really depends on the nature of the application being developed. In our case, because of the 2nd level priority of the database functionality (2nd priority here means that FinanceCAD is a Design tool first, then a financial Analyst) I don't believe it would be worth the while to create low level API database calls. So our choice of language will have to consider easy connectivity to the database we'll be using.

Let's just stop at these three features because they should be enough to make our choice of language. Of course not all projects would allow you to make a decision based on three features, but in the case of an Autocad like application, like FinanceCAD is, these three features should be quite enough to come to a decision. To recapitulate, we want a language that is very fast on graphics, can be ported at least to the linux platform without the need to rewrite the whole application from scratch and while keeping the porting effort to a minimum. And we want a language that can connect to a database quite easily and trouble free. Let's look at some of the languages available and see what features they offer.

Ada Programming Language:
The Ada language is among the oldest language available today. However it is also the language that has passed the test of time with flying colors. Originally developed by the American Department Of Defense as a better language for military applications, it now offers these features as an all purpose development language. Ada is truely at it's best in embedded system and long lived system. It is designed to be fast, efficient while being the most readable language to date. It excels where the programmer that is modifying the code is not necessarily the programmer that created it. This is where readability of code is of highest importance and Ada was specifically designed for this type of project. It's greater features are it's data structures, it's tasking model, and it's version of Object Oriented Programming Paradigm. Ada has no problem being compiled on many of the platforms that are available today. A few of the well known Ada compiler vendors are: AdaCore Technologies, Aonix and RR Software.

BASIC Programming Language:
Well BASIC (Beginner's All Purpose Symbolic Instruction Code) pretty much speaks for itself. It's a language designed to be learned quickly to say the least. As such it is usually very limited in terms of keywords and usage. However there are many exceptions today that tend to push BASIC as a considerable alternative to other languages. Today BASIC is now compiled to native code which gives it a speed feature that cannot be ignored at least in some cases. Today's BASIC is Object Oriented, most windows implementation have a strong integrated support for databases and reporting technologies. All in all BASIC compilers should be considered for many database applications because of the speed of development that they usually offer. The flaw in commercial BASIC compilers is that most have limited multiplatform abilities. To name a few BASIC implementation are: Power Basic™, Microsoft VisualBasic™ and PureBasic.

Pascal and ObjectPascal Programming Languages:
Pascal started out as an excellent learning language, at least it was it's original goal at the time. Since it first came out however, Pascal has seen many incarnations and is getting some very good scores as far as all around performances go. It offers solid Object Oriented Extensions thanks to the ObjectPascal implementation and offers a great feature called inline assembly (for those really low level programming needs). Because of it's teaching origins, Pascal and ObjectPascal are language that have a very strong and defined structure, this helps a great deal in making code that is organized and readable. The best known Pascal Compiler is of course Borland Delphi™ and Borland Kylix™ for the Linux platform.

The Java Programming Language:
Java is the latest craze in the programming industry. it is also the newest and is fast becoming the prefered language for all online development. In my opinion, Java is getting more credit than it deserves because in my experiences, Java is not the fastest language available. the language is nice to code in however and I believe that this is it's strong point as far as it's popularity goes. As an online language it's performances are adequate. But As a compiled language, it is far from the fastest alternative available. Perhaps, speed and performance should be the only goal of the next release of Java. Commercially, only Borland JBuilder™ is worth the attention in my most humble opinion.

C and C++ Programing Languages:
These are by far the most widespread of all languages available today. I believe C and C++ are the most opportunist languages there ever was. Most C programmers will swear by C and C alone. Same thing for C++ programmers. Notice that I tend to seperate the two languages. I do have a reason for it, C is not C++ and C++ doesn't have C in it. In other words, these languages took very independant branches when C++ was first implemented and that hasn't changed since. C and C++ are renouned for their speed and performances. They are also known to be the most crytic and non readable languages available today. C++ integrates the STL (Standard Template Library) and that gives it part of it's power. As far as commercial compilers go however, I haven't found one that was truely multiplatform. One comes close as far as Linux and Mac OS X and that is the XL C/C++ developed by IBM. Like Ada, C/C++ benifit from a large userbase and an OpenSource C++ community that keep the language striving and accessible to people that don't necessarily have the big budgets to buy the commercially available compilers with today's price tags. In my opinion, C and C++ should be used in conjunction with the other languages where there is a real need of performance. However, programmers could use Assembly language to even more performance gains. There are two well known commercial C/C++ compilers. There is Microsoft Visual C++™ and Borland C++ Builder™.

Before you go ahead and wonder why I haven't mentionned any other language as a feasible solution, you need to remember that this series is aimed at professional and commercial application development. In this context I have stopped my suggestions to what is commercially available only. I know there are many other languages, each with their own set of features and I believe each language is a work of art and art is a question of taste. One thing I don't like is a group of programmers of a language bring other languages down because they are not the language they would choose to program in. So this is not the object of this series of documents. The object is to give you, the professional programmer a lead on what's available out there. If you choose whatever language, it really doesn't matter to me as long as the language you choose gets the job done for you. In this document I'm just trying to give you a few pointers to help make sure you select the language that is truely suited for your particular big scale projects. With this information there are two more things we need to cover for FinanceCAD and for alot of other projects as well. There is the issue of finding a good multiplatform GUI library so that the visual aspect of the application can be ported with minimal to no effort between the platforms we will want to support. And the issue of which database we could use for our database and reporting purposes. Let's get right into it shall we?

ARE THERE GOOD MULTIPLATFORM GUI LIBRARIES:

This questions ringed in my head many times in my career. The biggest issue, when it comes to multiplatform development projects is none other than the user interface, the visual aspect of the application. Windows™, KDE, Motif, Gnome, Mac OS X all have specific functionalities available as far as how controls are built, drawn and managed at the operating system level. If there weren't any good multiplaform GUI (Graphical User Interface) multiplatform libraries out there, this would surely raise alot of concerns at pretty much all phases of the development cycle. Surprisingly, my recommendations here are not all at the commercial level as it seems that the libraries I will be suggesting here seem to offer better control and a better coding experience than anything I've seen commercially available. Of course, if you are creating a text mode application or a 100% GUI independant graphical application then the issue of multiplatform GUI is irrelevant in your particular case. We will be looking at four widely used GUI libraries so that you know of their existence for one thing and that you have a brief overview of how it works and how you could potentially use it in your application projects.

The Qt Class Library and tools: [Commercial]
The Qt Class Library and tools is my only commercial recommendation. In the words of the website: "Qt is a complete C++ application development framework. It includes a class library and tools for cross-platform development and internationalization. It achieves its goal by abstracting low-level infrastructure functionality in the underlying window and operating systems, providing a coherent and logical object-oriented interface that makes sense to programmers". From what customers seem to say from this library, it comes highly recommended because of it's relatively small learning curve for the capabilities that it offers.

The wxWindows GUI Development System: [OpenSource]
The wxWindows System is what seems to be a highly object oriented based hierarchy of GUI objects that are designed to be drawn independantly of the operating system they are executed under. Although an opensource solution, wxWindows is used in many commercial applications already, and the main reason is performances in a multiplatform GUI library. From what I've seen, wxWindows offers many more controls than even Qt (see above) and the inner organization of the hierarchy of control object is logical and sensible. I would recommend it for a vast range of application development. Take a look around on the website, don't just take my word for it, see for yourself why wxWindows is listed in my recommendations.

GTK (Gimp ToolKit) Library: [OpenSource]
The The Gimp ToolKit is probably the most widely spread OpenSource multiplatform GUI toolkit I've ever seen. Another important aspect is that it's probably the toolkit that can be used by the widest list of programming languages. If it wasn't for the need to tweak the library in order to get it to perform reasonably on the speed scale, this toolkit would have been strongly recommended. Indeed this one is not for anybody to just install and use efficiently. Users do report that when tweaked appropriately, the performance of the application rivals those offered by the other toolkits or even faster, I have no personal experience using GTK so I'll just have to take the time to tweak it myself to make my own judgement, if they are right, perhaps GTK would deserve your time to take a serious look at.

TCL/TK (Tool Command language/ ToolKit): [OpenSource]
The TCL/TK (Tool Command language/ ToolKit) is part of my recommendations because it has it's very unique means of creating a user interface. It is a scripting language, in essence, and what it creates can be used in a good range of programming languages. People that use TCL/TK can't help but brag about it's features and methods of doing things so because of that royalty from it's users, I had to recommend it if not for any other reason, so that you know it's there, it's different, and it's definitaly worth looking at. There is alot of reference available on the internet that you can learn from so that gives it another good reason to be considered.

These are the four toolkits I can recommend. If you take a look at the links I provide to each of them, you can get a much better picture of what the toolkits are capable of and where they have been used so far. You will aslo be able to make a better judgement as to which library you should consider for your programming project. Just remember that, as you can see, there are tools and libraries available to greatly help you when the time comes to port your project to other platforms.

WHAT ARE MY CHOICES FOR A GOOD DATABASE MANAGEMENT SYSTEM:

The first thing I can say about the databases is that they all do one thing in common. They all serve to manage databases and each databases consists of table structures, primary keys, indexes and the likes to present the data in desired orders and to allow to quickly locate records in the tables. All the databases I am recommending here also offer SQL (Structured Query Language) which allows for a complete range of database maintenance functions and reporting purposes. In order to select the right database for the job, you need to take a look at the exact reasons why your project would be using the database in question. How powerful does it really need to be to meet your specific needs depends on what the needs are to begin with. There are 6 database I would like to recommend you look at. 3 of them are commercial products, the others are OpenSource (for OpenSource projects) and have licenses available for commercial development using those database systems).

The Oracle Database System: [Commercial]
Oracle has been there since pretty much the dawn of the PC industry. It offers a complete range of features as far as databases are concerned. For example, it has SQL (Structure Query Language) for database interrogation, stored procedures you name it. Oracle is typically installed on a Unix or Linux server and can be easily accessed from Microsoft Windows™. It's performances speak for themselves and it is used in places where reliability is of high priority. Oracle features a rich set of tools and utilities to help the maintenance of the databases and the generation of queries and report to give it's users full control of the data and it's processing.

The Sybase Databases: [Commercial]
The Sybase Databases are offered in two flavors so to speak. There is the classic Sybase Database Management System and Sybase SQL Anywhere (specialized in portable computing and data replication). Like Oracle, the classic Sybase Database is typically installed in a Unix or Linux environment and offers pretty reliable and secure database management system. For the Windows™ platform, connecting to Sybase is as easy as having the right connection string. Sybase offers stored procedures, SQL for it's queries and a good user interface, a bit easier to learn in my opinion than Oracle that offers intuitive means of creating and maintaining your databases.

Microsoft SQL Server™ Database Management System: [Commercial]
The The SQL Server Database Management System has already been available for quite some time now. In my experience it is by far the easiest to learn and still Microsoft managed to pack a full range of features and a full range of application to help you in your database management and database programming endeavours. As far as FinanceCAD is concerned, the face that SQL Server is only available for Windows pretty much eliminates it for a central database. Or at least it would mean that table structures, relationships and indexes will need to be converted to the new database for the other platforms.

The MySQL Database System: [OpenSource/Commercial licenses]
The The MySQL Database System is probably the closest cousin to SQL Server that you will ever see. The SQL syntax is very close to SQL Server so migrating the database between the two databases is almost a sinch. MySQL can be installed in Windows and Linux so portability between those platforms are as good as they get. If you are to develop a commercial application with MySQL as your database however, you will have to contact them to purchase a commercial license of the product. At the time of writing, MySQL doesn't support stored procedures, however, it will in the next major release of their product.

The PostGreSQL Database System: [OpenSource]
The PostGreSQL Database Management System is probably the oldest freely available database management system available. As such, one can say it is also the most tested of them all hence the safest to use in all of the free database systems. That's not far from the truth and many applications developed to support MySQL as their database are starting, more and more, to offer the usage of PostGreSQL as well. As far as SQL goes, it's implementation in PostGreSQL is still SQL 89 compliant whilst the other databases are typically at leas ANSI SQL 92 compliant. But that doesn't stop it from being a good all around reliable database to use. It can be installed in any Linux configuration and version so compatibily isn't really an issue.

The Firebird Database Management System: [OpenSource]
The Firebird Database Management System is the OpenSource version of the well known Borland Interbase version 6.0. As a follower to a commercial product now available freely through the OpenSource community, Firebird offers some very advanced features as is expected in a commercial quality product. It has stored procedures and has had them for a while now. I still fail to see why this database is not more widespread than it is. But if you sit down and compare features you'll be tempted, like many before you, to consider Firebird quite seriously and rightfully so. It installs in Windows™ and Linux so it answers the call of our multiplatform criteria quite well. As many other OpenSource projects, there is no ownership, no one is responsible for any error produced by the database system and that is often a show stopper in teh commercial world. Me, if it does the job, I would have no problem recommending it.

There are of course other databases available. These seem to be the most widely used and that is basically why I recommended those. Depending on the database needs however you might find other databases outthere that answers your needs without giving you all the power that are offered by those listed above. For example, I can think of two systems that offer their databases as engines that you can include with your appliation, they are smaller, and probably faster (for smaller database tasks) than the 6 listed. They are SQL Lite and Suneido. It all depends on your specific database needs. So to know which database you should use, you need to know exactly what you'll be doing with the database as in it's specific role in the application. You can find this kind of information in the detailed analysis and the application model but usually, the detailed analysis is where it should at least first appear.

AND IN CONCLUSION:

That was a big chunk of theory I threw at you in this part of the series. You might want to reread this a few times and take the time to visit the links I provided to get better acquainted with the products that you can choose from and do a little research just so that when you need to use this theory, you'll be a bit better equipped to make the choices that will drive your project to it's success. I think that by now you noticed that I always seem to be pushing the need to be as prepared as you can be between the different parts of the application development process. You're right, I am pushing this, with a good reason too. I strongly believe that being prepared is the only way to take on a project of these sizes (the big scale projects). You have to think in terms of what you have versus what you need. the more closely these two lists follow each other, the less questions you'll have to ask later and the less research you'll have to do at a later time in the project. The less research in the analysis, the faster the analysis can be completed, and this rolls off and accumulates itself throughout the whole development cycle too. All the time you can save at the beginning will shorten your project's development life. If you are developing a commercial product, I'm sure you know that especially in that case, time is of the essence. You need to get things done fast, and right. And the better you can do that, throughout the development process, the better for the project and for you too, of course.

In the next section, we will be looking at that ever eternal phase I "not so affectionately" like to call "testing and debugging". Yes, every programmer's nightmare, it is unevitable no matter how well intensionned you and your development team are, sooner or later, you will fall into this phase. Rest assured however, there are many tools to help you out in that phase too. We'll see what they are and the role they play. We'll also see how to best prepare for that phase too (indeed preparation plays an important role here as well). So until then, if you have questions and comments, by all means, do email me and we'll see what we can do to clear things up for you. Happy reading and see you in the next section.

MystikShadows
Stéphane Richard
srichard@adaworld.com

Check out Issue #9 for parts 1 and 2, or download a copy of this tutorial.

Genre	Votes	Percent	Graph
Bob Saget Killer 2000 M \ K Productions	7	14.9%
Dark Ages I Michael Hoopman	2	4.3%
The Game Tsugumo	3	6.4%
FoX Terminator_Z	3	6.4%
Elysian Fields Pantera55	4	8.5%
Lianne in...the Dark Crown DarkDread	2	4.3%
Legend of Lith II DarkDread	1	2.1%
Hack-Man 3 WisdomDude	5	10.6%
Mini RPG 2 / 3 Jaws-V-Soft	10	21.3%
Dark Woods 2 Jocke The Beast	10	21.3%
47 Total Votes

Word	Common Misspelling(s)
definitely	definately (I see this one two or three times on an average day...if you don't get anything else out of this, remember this one!)
tried	tryed

Word	Common Misuse
decent	recursive decent parser (should be "descent")
there, they're, their	All three of these are commonly interchanged when they shouldn't be. "There" is a location, "they're" is a contraction for "they are", and "their" is a possessive adjective.
then, than	"Then" and "than" are interchanged often. "Then" is a time or conditional ("I ate lunch, and then I went home"); "than" is an adjective ("I ate more than George.").
it's, its	Commonly interchanged. "It's" is a contraction for "it is" ("It's cold outside."); "its" is a possessive adjective ("Its wheels were round.").
who's, whose	Commonly interchanged. "Who's" is a contraction for "who is" ("Who's eating the apple pie?"); "whose" is a possessive adjective ("Whose apple pie is that?").
to, too	"To" is a preposition; "too" is a comparative adjective. "I went to the store"; "I drank too much."
your, you're	"Your" is a possessive adjective ("This was your idea."); "you're" is a contraction for "you are" ("You're so smart.").
Zelda	Usually used by Nintendo newbies when speaking of Link in the Legend of Zelda series.
effect, affect	"Effect" is a noun meaning "the result of an action" ("The effect of excessive drinking is a hangover."); affect is a verb meaning "to manipulate in some way" ("I wish my ranting would affect these people.")
good, well	"Good" is an adjective ("You are a good reader."); "well" is an adverb ("I did well on the test.").

Word	Why it's wrong
themself	This word does not exist in the English language. "Them" is plural; it cannot be used to refer to one person. Therefore, "themself" cannot logically exist. "Themselves" is the usual correct replacement, but the structure of the entire sentence must be considered in such a situation; an entirely different word or phrase or even restructuring of the sentence might be in order.

“Grand Prize” plaque (for 1st place!!)
“Silver Prize” plaque (for 2nd place)		“Bronze Prize” plaque (for 3rd place)

QB Express

Issue #10 ~ May 26, 2005

In This Issue

From The Editor's Desk

Written by Pete

Submit To QB Express

Letters

Letter From MystikShadows

Letter From Jacob Palm

Letter From aetherFox

Letter From nitro2k01

Letter From anarky

Express Poll

What is the most overrated QB game?

News Briefs

Site News

Project News

Other News

Gallery

Written by Pete

ASCIIQUEST Editor v1.0

Review of Battle Pong by Lithium

Written by Adigun Azikiwe Polack

G A M E • S Y N O P S I S

T H E • B R E A K D O W N

T H E • F I N A L • V E R D I C T

AI: Artifical Stupidity

Written by aetherFox

ASCII-WORLD Competition Follow-Up

Organized by lurah and MystikShadows

So What The Heck Is Fun Anyways?

Written by Deleter

The BASIC User's Guide to English Spelling and Grammar

Compiled by DrV, Unofficial Master of the English Language

Commonly Misspelled Words

Commonly Misused Words

Just Plain Wrong Words

Conclusion

QBasic GUI Development

Written by Jacob Palm

Intro

What a good GUI should have

Tips

Links to GUI pages

That's it for now

Monthly Awards

Written by Pete

Site of the Month

Programmer of the Month

FreeBASIC Ultimate Demo Compo:the brighter new gala of the FB demoscene!

Written by Adigun Azikiwe Polack

Comics

By Rattrapmax6

I.F. Games Chapter 5:"Teaching English to our computer"

Written by Na_th_an

Coding the Parser Module

Auxiliary functions

We need a dictionary!

Coding the interpreter

How the player command interpreter works

Tips for creating a dictionary

Coding Techniques in FreeBasic: Part 1Variables and Var Initializers

Written by VonGodric

1. Variables and Var Initializers

THE ART OF DATA VALIDATION

Written by Stéphane Richard (Mystikshadows)

INTRODUCTION:

DATA VALIDATION DEFINITIONS AND CONCEPTS:

THE MANY TYPES OF DATA VALIDATION:

REMOVING/MINIMIZING HUMAN ERRORS:

THE FINAL WORD:

Writing A Simple BASIC Interpreter:Lesson #02

Written by Vincent Peters (BazzokaSquirrel)

PROPER ERROR MANAGEMENT IN FREEBASIC

Written by Stéphane Richard (Mystikshadows)

INTRODUCTION:

WHAT EXACTLY IS ERROR MANAGEMENT:

WHAT TO DO WHEN AN ERROR IS ENCOUNTERED:

HOW TO CODE FOR THE ERRORS IN FREEBASIC:

AND IN CONCLUSION:

FreeBASIC Ultimate Demo Compo:
the brighter new gala of the FB demoscene!

I.F. Games Chapter 5:
"Teaching English to our computer"

Coding Techniques in FreeBasic: Part 1
Variables and Var Initializers

Writing A Simple BASIC Interpreter:
Lesson #02

Coding A Parallax Scrolling Platformer
Chapter #1: INTRODUCTION

COMMERCIAL AND PROFESSIONAL APPLICATION DEVELOPMENT
Part Three - The Conceptualization Process

COMMERCIAL AND PROFESSIONAL APPLICATION DEVELOPMENT
Part Four - From Conceptualization To Application