Q47780: Blinking Text May Be Eliminated with BIOS Call

Article: Q47780
Product(s): See article
Version(s): 5.00 5.10
Operating System(s): MS-DOS
Keyword(s): ENDUSER | S_QuickC S_QuickASM EGA | mspl13_c
Last Modified: 16-JAN-1990

Blinking text can be accessed by setting the foreground text color to
a value of 16 or greater. However, this can be affected by a BIOS call.
BIOS call 10, subfunction 3 toggles the interpretation of the
intensity bit of the foreground color. By making a call to this BIOS
function you can access additional background colors. Without blinking
foreground text, you can access 16 background colors. With blinking
text you are limited to 8 background colors. The program shown below
demonstrates this.

The example prints 16 lines of text with varying background colors.
The intensity interpretation is then toggled, limiting the output to
only 8 background colors.

This problem also occurs in Microsoft QuickC Versions 1.00, 1.01,
2.00, and 2.01.

Sample Program:
--------------

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

#define TRUE 1
#define FALSE 0

void toggle_intensity(int);

void main(void)  {
   long i;
   char buf[80];
   _clearscreen(_GCLEARSCREEN);
   toggle_intensity(0);
   for (i=16; i < 32; i++) {
      _setbkcolor (i);
      _settextcolor (i+1);
      _settextposition (i-15, 10);
      sprintf(buf, "  Background = %2ld  Foreground = %2d  \n",i,i+1);
      _outtext (buf);
   }
   getch();

   _setbkcolor (_BLACK);
   _clearscreen(_GCLEARSCREEN);
   toggle_intensity(1);
   for (i=16; i < 32; i++) {
      _setbkcolor (i);
      _settextcolor (i+1);
      _settextposition (i-15, 10);
      sprintf (buf, "  Background = %2ld  Foreground = %2d  \n", i, i+1);
      _outtext (buf);
   }
   getch();
}

/*  If onoff is True, intesity bit will indicate blinking text  */
void toggle_intensity(int onoff)  {
    #define         VIDEO_IO        0x10
    #define         BIOS_CALL       0x10
    #define         INTENSITY_TGL   0x03
    union REGS regs;

    regs.h.ah = VIDEO_IO;
    regs.h.al = INTENSITY_TGL;
    if (!onoff)
       regs.h.bl = 0x0;
    else
       regs.h.bl = 0x1;
    int86 (BIOS_CALL, &regs, &regs);
}

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