Acid Works Programming Tips Page

Here are some really good QBasic programming tips. If you have any tips you would like me to add(you will get credit) email them to me.

Graphics | Keyboard | Math | Timing

Graphics

Use "WAIT &H3DA, 8" before updating the screen, it allows the screen time to refresh and helps animation appear flickerless.
SCREEN 13 is best for games, it has 256 colors and has had many libraries written for it.
When using SCREEN 13 use the following instead of PSET, it is much faster.
```
   DEF SEG = &HA000
   POKE X + (Y * 320&), color 
   DEF SEG
  
```

Is SCREEN 13 use this instead of PALETTE, it is much faster and easier to use:

   OUT &H3C8, color to change
   OUT &H3C9, red value(a number from 0 to 64)
   OUT &H3C9, green value(a number from 0 to 64)
   OUT &H3C9, blue value(a number from 0 to 64)

Also to find out what values a color has use this:

   OUT &H3C7, color to find
   red value = INP &H3C9
   green value = INP &H3C9
   blue value = INP &H3C9

When using PUT remember that PSET is the fastest option.

To save the screen to a file in mode SCREEN 13 do:

   DEF SEG = &HA000
   BSAVE "insert file name here", 0, 64000
   DEF SEG

And to load that screen back up again do:

   DEF SEG = &HA000
   BLOAD "insert file name here", 0
   DEF SEG

Keyboard

Try using "keycode = INP(&H60)" instead of "keycode$ = INKEY$", it is much faster.
To clear the key board buffer and get rid of the annoying beeping sound, do this:
```
   DEF SEG=0: POKE &H41A, PEEK(&H41C)
  
```

To disable CTRL+BREAK and CTRL+C do this:

   DEF SEG = 0
   FOR x = 0 TO 3
    POKE (108 + x), PEEK (112 + x)
   NEXT

Math

Try to use integers(% and &) instead of floating point(! and #) numbers, they are much faster.
When dividing integers use "a \ b" instead of "INT(a / b)"
If you can add numbers("a + a") instead of multiplying("a * 2"), adding is much faster.
Also multiplying("x * x") is faster than raising a number to a power("x ^ 2").
To find out if a number is odd do "x AND 1", if it returns 1 it is odd.
You could also do "x MOD 2" to find out if a number is odd, if it returns 1 it is odd.
To find out if a number is divisible by another number do "x % y", if it returns 0 x is divisible by y.
Instead of doing "b = x : x = y : y = b" to swap the numbers x and y, do "SWAP x, y"

Timing

This can do about 1/70 of a second timing, but it depends what Hz rating your monitor is set at.

   SUB DELAY (seconds!)
    FOR a = 0 TO 70 * seconds!
     WAIT &H3DA, 8	
     WAIT &H3DA, 8, 8
    NEXT a
   END SUB

This one does about 1/19 of a second on all computers.

   SUB DELAY (seconds%)
    seconds% = seconds% * 19
    DEF SEG = 0
    POKE (1132), 0
   CountDown:
    IF PEEK(1132) < seconds% THEN GOTO CountDown
    DEF SEG 
   END SUB