PRODUCT  :  Borland C++                            NUMBER  :  716
  VERSION  :  2.0
       OS  :  DOS
     DATE  :  October 19, 1993                         PAGE  :  1/4

    TITLE  :  Switching Between 25 and 43 Line Mode on EGA




  /*************************************************************
     This program shows how to switch between 25 and 43 line mode
     on an EGA.
  *************************************************************/

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

  #define OFF 0
  #define ON  1
  #define NOCHANGE 2

  #define TRUE  1
  #define FALSE 0

  void normvideo(void);
  int  in43linemode(void);
  void ega43(int mode);
  int  egainstalled(void);
  void setcursor(unsigned char start, unsigned char end);
  int  egacursoremu(int mode);
  int  egacursorsize(void);
  extern unsigned char _video[];
  void main(int argc, char *argv[])
  {
      int toggle = NOCHANGE, i;
      _video[3] = 42;
      _video[7] = 43;
      if (!egainstalled()) {
          fprintf(stderr, "EGA not installed.\n");
          exit(1);
      }

      if (argc >= 2)
          switch(argv[1][0]) {
              case '?': toggle = NOCHANGE;
                        printf("usage: EGA43 [1][0]\n"
                               "1 = 43-line mode; "
                               "0 = 25-line mode; "
                               "no argument = toggle mode\n"
                              );













  PRODUCT  :  Borland C++                            NUMBER  :  716
  VERSION  :  2.0
       OS  :  DOS
     DATE  :  October 19, 1993                         PAGE  :  2/4

    TITLE  :  Switching Between 25 and 43 Line Mode on EGA




                        printf("43-line mode: %s\n",
                                in43linemode() ? "ON": "OFF");
                        printf("Cursor size : %d\n",
                                egacursorsize());
                        break;
              case '0': toggle = OFF;
                        break;
              case '1': toggle = ON;
                        break;
              default : toggle = NOCHANGE;
           }



      if (argc == 1)
          switch(in43linemode()) {
              case TRUE:  toggle = OFF; /*if already on, turn off*/
                          break;
              case FALSE: toggle = ON; /* if already off, turn on*/
                          break;
          }

      if (toggle != NOCHANGE) normvideo();

      if (toggle == ON)  ega43(ON);
      if (toggle == OFF) ega43(OFF);
      for (i=0;i<43;i++) cprintf("%d\r\n",i);
      getch();
  }


  void normvideo(void)
  {
      union REGS regs;

      regs.h.ah = 0;
      regs.h.al = 3;
      int86(0x10, &regs, &regs);

  }

  void ega43(int mode)
  {













  PRODUCT  :  Borland C++                            NUMBER  :  716
  VERSION  :  2.0
       OS  :  DOS
     DATE  :  October 19, 1993                         PAGE  :  3/4

    TITLE  :  Switching Between 25 and 43 Line Mode on EGA




      union REGS regs;

      if (mode == OFF)
          regs.h.al = 0x11;
      else
          regs.h.al = 0x12;

      regs.h.ah = 0x11;
      regs.h.bl = 0;

      int86(0x10, &regs, &regs);

      egacursoremu(mode);
  }

  int egainstalled(void)
  {
      union REGS regs;

      regs.x.ax = 0x1200;
      regs.x.bx = 0x0010;
      regs.x.cx = 0xFFFF;

      int86(0x10, &regs, &regs);

      if (regs.x.cx == 0xFFFF)
          return(FALSE);
      else
          return(TRUE);
  }

  void setcursor(unsigned char start, unsigned char end)
  {
      union REGS regs;

      regs.h.ah = 1;
      regs.h.ch = start;  /* starting scan line */
      regs.h.cl = end;    /* ending scan line   */

      int86(0x10, &regs, &regs);

  }














  PRODUCT  :  Borland C++                            NUMBER  :  716
  VERSION  :  2.0
       OS  :  DOS
     DATE  :  October 19, 1993                         PAGE  :  4/4

    TITLE  :  Switching Between 25 and 43 Line Mode on EGA




  int egacursoremu(int mode)
  {
      unsigned char far *emulation = MK_FP(0x40,0x87);

      if (mode == OFF) {
          *emulation &= ~0x01;
          setcursor(6, 7);
      }
      else {
          *emulation |= 0x01;
          setcursor(5, 7);
      }

      return(mode);
  }

  int in43linemode(void)
  {
      unsigned char far *egamode = MK_FP(0x40,0x84);

      return ( (*egamode == 42)? TRUE: FALSE);

  }

  int egacursorsize(void)
  {
      unsigned char far *size = MK_FP(0x40, 0x85);

      return( (int) *size);
  }


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  subject to the terms of the No-Nonsense License Statement that
  you received with the Borland product to which this information
  pertains.