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Q42079: Getting 43-line Mode for C and QuickC Graphics

Article: Q42079
Product(s): See article
Version(s): 5.10
Operating System(s): MS-DOS
Keyword(s): ENDUSER | s_quickc | mspl13_c
Last Modified: 15-JAN-1990

The Microsoft C Version 5.10 Optimizing Compiler README.DOC file
states the following:

   The graphics library new functions correctly in 43-line mode on an
   EGA, and in 43-line, 50-line, and 60-line modes on a VGA.

This information is correct; however, it does not state that you must
write your own interrupt routine to set the video mode to support
this.

The following program demonstrates using Int 10H, Function 11H,
Subfunction 23H to set an EGA system into 43-line mode. The interrupt
call must be made BEFORE the call to _setvideomode(). If the routine
is called after _setvideomode(), the text height is changed, but the
program uses only the first 25 lines of the screen.

The same procedure also works with the QuickC Version 2.00
Presentation Graphics package, for placing additional text (with
_outtext) around the chart. It does not change any of the default text
(which already has the text height of 43-line mode), or change the
appearance of the chart, but it allows additional text to be added
around the chart in the smaller font to create a uniform appearance.

The following is a sample program that demonstrates 43-line mode:

/* program line43.c */

#include <conio.h>
#include <stdio.h>
#include <graph.h>
#include <dos.h>
#include <process.h>

union REGS inregs, outregs;
struct SREGS segregs;
int result;

void main(void)
{
  inregs.h.ah = 0x11;      /*load Function # into AH register       */
  inregs.h.al = 0x23;      /*load SubFunc # into AL register        */
  inregs.h.bl = 0x03;      /*load constant for 43-line mode into BL */
                           /*For 50-line mode, use                  */
                           /*       inregs.h.bl=0x00;               */
                           /*       inregs.h.dl=0x32;               */

  int86x(0x10, &inregs, &outregs, &segregs);  /* call interrupt */

  _setvideomode(_ERESCOLOR);   /* 640x350 EGA graphics mode         */
                               /* For VGA w/50 lines, change to:    */
                               /* _setvideomode(_VRES16COLOR);      */
  _settextposition(30,30);
  _outtext("this should be tiny text!");
  while(!kbhit());
  _setvideomode(_DEFAULTMODE);  /* restore to default mode  */

Note: The "IBM ROM BIOS" quick-reference guide states that this
function should be used only AFTER a _setvideomode command. However,
this does not work effectively with the C graphics library.

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