In allegro, if you press too many keys at the same time the keyboard stops responding properly, beeps, and even occasionally gives error messages (secondhand report; it never happened to me). This isn't really a problem because most games don't require you to press more than three keys at any one time, and allegro can handle that most of the time. But what about splitscreen? In a splitscreen game, having six keys pressed at the same time is relatively common ... and some keyboards / computers just can't handle this with allegro's standard input checks. Is there any command set or method I can look into that handles large amounts of simultaneous keyboard input?

I know this has been done before ...

[ January 02, 2002: Message edited by: Zaphos ]

No no ... I've seen games that get very good input for two-player splitscreen ... and Gemini posted, before:
quote: However, some programs like Impulse Tracker for DOS can have so many keys held down at once it's just amazing. I've seen IT register over 20 keys at once before! (It has a debugger for its keyboard routines which shows the HEX values of all the keys and lights up those which are held down.) Now, if someone could get in touch with the guy who coded those routines and impelement them into Allegro, it would be soooooo sweet.
So it isn't completely the hardware ... it might be the OS, but I kinda doubt that ... so it should be possible to get very high quality keyboard input ... the question is ... how?

The cheap IBM keyboard is not for exciting-action game.
I suggest buy a Microsoft SIDEWINDER FreestylePro joypad!
[ January 03, 2002: Message edited by: Johnny13 ]

Unfortunately, it is a hardware limitation. It's because of the way keyboards are built. To remain cheap, they use electrically conductive ink instead of wires. This works fine if you have only one button, or several buttons with only one being pressed at a time. However, you can't make diodes with ink - so it is possible for you to press three keys but the keyboard detects 4 of them pressed at a time (sometimes more). The keyboard logic detects this situation (if num_pressed_keys > 3), and ignores any subsequent key presses, since they might be "ghost" keys.
The software on the other hand is perfectly capable of dealing with any number of simulatious key presses. The fact that IT can be shown to work with many keypresses at a time was probably due to the exceptional (or very old) keyboard that was being used.