16 color cga mode 1/2

 BBS: Inland Empire Archive
Date: 04-10-93 (02:18)             Number: 157
From: MATT PRITCHARD @ 930/21      Refer#: NONE
  To: ALL                           Recvd: NO  
Subj: 16 color cga mode     1/2      Conf: (1) 80xxx

Here is a reprint of an old message on 16 color CGA 160x100 graphics.

The code is QuickBASIC, but should be understandable.
============================================================
========

The following four messages are an example of how to
program in the 160x100 16-color CGA mode.  This mode is not
supported by BIOS on standard PCs and PC clones, although
it is supported on the PC Jr.  No attempt to test the code
on a PC Junior has been made, simply because I have no
access to one.

DEFINT A-Z

DECLARE SUB ScreenMode160 (Mode%)
DECLARE SUB ClearScreen (Mode%, DrawColor%, NoClear%)
DECLARE SUB ExitMode () DECLARE SUB DrawDot (x%, y%,
DrawColor%) DECLARE SUB DrawLine (x1%, y1%, x2%, y2%,
DrawColor%) DECLARE SUB GetInput () DECLARE SUB Pause ()

RANDOMIZE TIMER

'       SuperCGA version 1.0
'       Color Graphics Adapter Enhancement Routines '
Tesseract Productions '

'   BEGIN (main)

SCREEN 0, 0, 0: WIDTH 80

PRINT "Super CGA"
PRINT "Version 1.0"
PRINT "Tesseract Productions"
PRINT "Programmed by Lawrence McAlpin"
PRINT ""
PRINT "Demonstration program on the 160x100 128-color capabilities of the
CGA" PRINT "monitor.  Tested on an AT&T PC 6300 with built-
in AT&T CGA and a" PRINT "Verxion 386 with BOCA SuperVGA."
PRINT PRINT "WARNING! This program may not work properly on
emulated CGA sreen" PRINT "modes (i.e., it may not work
right on EGA, VGA, MCGA, or XGA cards.)" PRINT "The author
assumes no liability for any damag that may result from"
PRINT "the use of this program.  If you try this program
out you are" PRINT "responsible for anything that may
occur." PRINT PRINT "128 Color CGA Demonstration Program"
PRINT PRINT "Hit '+' or '-' to change the 'background'"
PRINT "Hit 'L' or 'l' to draw random dots and lines" PRINT
"Hit 'M' or 'm' to change between box and fuzzy modes"
PRINT "Hit 'Q' or 'q' to quit" PRINT "PRESS ANY KEY TO
CONTINUE" Pause

ScreenMode160 1
ClearScreen 1, 0, 0
DrawLine 0, 1, 79, 1, 3
DrawLine 0, 1, 0, 79, 3
DrawLine 3, 1, 40, 80, 4


'   demonstrate the first 128 colors

FOR counter = 0 TO 79
    DrawDot counter, 15, counter
NEXT counter
FOR counter = 80 TO 127
    DrawDot counter - 80, 20, counter
NEXT counter

GetInput

'   Pause

'   there are two types of screen 'modes' '   they are box and fuzz,
ScreenMode160 and ClearScreen take the mode '   parameter
for box as zero, and fuzz for anything else '   fuzz mode
smooths the box-graphics so they don't look AS boxy as they
'   really are

ClearScreen 1, 0, 0

'   this returns you to the regular 320x200 CGA 4-color
mode '   if you neglect to ExitMode then you will find your
screen display '   acting extremely strangely as the
registers won't be restored to '   something normal

ExitMode

'   END (main)

END




SUB DrawDot (x, y, DrawColor)

 '  check for out of bounds errors

 IF DrawColor < 0 OR DrawColor > 255 THEN EXIT SUB
 IF x < 0 OR x > 79 THEN EXIT SUB
 IF y < 0 OR y > 99 THEN EXIT SUB

 a = ((2 * x + (y * 160)) AND &HFFFE) + 1
 n = PEEK(a)
 POKE a, (n AND &HF0) OR DrawColor

END SUB

DEFINT A-Z
SUB DrawLine (x1, y1, x2, y2, DrawColor)

IF ABS(x1 - x2) > ABS(y1 - y2) THEN
    IF x1 > x2 THEN
        SWAP x1, x2
        SWAP y1, y2
    END IF
    dx = (x2 - x1)
    dy = (y2 - y1)
    IF dx <> 0 THEN
        b! = dy / dx
    ELSE
        b! = 0
    END IF
    m! = y1 - x1 * b!
    FOR x = x1 TO x2
        IF b! <> 0 THEN
            y = INT(m! + x * b!) + .5
        ELSE
            y = y1
        END IF
        DrawDot x, y, DrawColor
    NEXT x
ELSE
    IF y1 > y2 THEN
        SWAP y1, y2
        SWAP x1, x2
    END IF
    dx = (x2 - x1)
    dy = (y2 - y1)
    IF dx <> 0 THEN
>>> Continued to next message
===
 * SLMR 2.1a * Yesterday I got so old

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