Liren Large Software Subsidy 7/07.iso/c/c072/1.ddi/PRG9_2D.C

C/C++ Source or Header | 1987-09-19 | 5.0 KB | 195 lines

/*Program 9_2d -- Display a clock on the screen w/ Keyboard Control
    by Stephen R. Davis, 1987

  This program should be compiled under the TINY memory
  mode and may then be converted into .COM file using the command:

  EXE2BIN PRG9_2D.EXE PRG9_2D.COM

  It can also be executed as an .EXE file.  Do not execute from IDE!

  This version adds the capability that the delta time can be
  hidden by entering '~' and cleared by entering '`'.  This is
  only intended as an example of a full TSR type program.
  (This version makes allowances for its own stack so that
   SSTACK should not be necessary.)
*/

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

#ifndef __TINY__
     #error Should use TINY compilation model
#endif

/*first the prototyping definitions*/

void interrupt clock (void);
void display (int, int, int);
void out (char *, int, int);
void interrupt screenout(unsigned, unsigned, unsigned, unsigned,
                         unsigned, unsigned, unsigned, unsigned,
                         unsigned);
void init (void);

/*define our data structures*/

union {
       long ltime;
       int stime [2];
      } p;
struct REGS regs;
void interrupt (*oldclock)(void);
void interrupt (*oldscreen)(void);
int prevtime, time, minute, hour, dflag, temp;
char buffer [6];

int far *screen;
char digits [] = {"0123456789"};

/*allocate space for our own stack area*/

int savess, savesp, sflag;
char stack [0x1000];

/*Clock - grab the interrupt and provide the function*/
void interrupt clock (void)
{
     /*put in our own stack*/
     if (!sflag) {
          savesp = _SP;
          savess = _SS;
          _CX = (int)&stack[sizeof(stack)];
          _SS = _DS;
          _SP = _CX;
     }
     sflag++;

     /*get the curren time (long format) using the BIOS call
       1a.  Divide this down into number of minutes (short
       format).*/
     regs.h.ah = 0;
     int86 (0x1a, ®s, ®s);
     p.stime [0] = regs.x.dx;
     p.stime [1] = regs.x.cx;
     time = (int)(p.ltime / (long)1092);

     /*now display the current time in 24 hour format*/
     display (time, 0, 75);

     /*then display the delta*/
     if (prevtime == -1)
          prevtime = time;
     if ((time -= prevtime) < 0)
          time += (24 * 60);
     if (dflag)
          display (time, 1, 75);

     /*pass control on to the next interrupt routine*/
     (*oldclock)();

     /*now restore caller's stack*/
     if (!--sflag) {
          _SS = savess;
          _SP = savesp;
     }
}

/*Display - put a time on the screen in the position indicated.
            Remember we can't do any DOS calls here.*/
void display (number, y, x)
     int number, x, y;
{
     hour = number / 60;
     minute = _DX;

     /*stuff this into an ascii buffer for output*/
     buffer [0] = digits [hour / 10];
     buffer [1] = digits [hour % 10];
     buffer [2] = ':';
     buffer [3] = digits [minute / 10];
     buffer [4] = digits [minute % 10];
     buffer [5] = '\0';

     out (buffer, y, x);
}

/*Out - out a string onto the screen w/o using system call*/
void out (buffer, y, x)
     char *buffer;
     int y, x;
{
     int far *scrptr;

     scrptr = screen + (y * 80 + x);
     while (*buffer)
          *scrptr++ = 0x1700 + *buffer++;
}

/*Screenout - examine characters being output using BIOS
              int 0x10.  When a '`' is encountered, clear
              the duration clock; if a '~' is seen, toggle
              the delta display on and off.*/
void interrupt screenout (bp, di, si, ds, es,
                          dx, cx, bx, ax)
     unsigned ax, bx, cx, dx, si, di, bp, ds, es;
{
     /*check for our characters:*/
     if ((temp = (ax & 0xff00)) == 0x0900
                        || temp == 0x0e00) {
          if ((temp = (ax & 0x00ff)) == '`')
               prevtime = -1;
          if (temp == '~')
               dflag = !dflag;
     }

     /*pass control onto BIOS routine to get character*/
     _AX = ax;
     _BX = bx;
     _CX = cx;
     _DX = dx;
     (*oldscreen)();
     ax = _AX;
     bx = _BX;
     cx = _CX;
     dx = _DX;
}

/*Main - install the above routine.*/
main ()
{
     init ();                          /*set screen pointer*/
     oldclock  = getvect (0x1c);
     oldscreen = getvect (0x10);
     setvect (0x1c, clock);
     setvect (0x10, screenout);

     keep (0, 0x1000);
}

/*Init - set the screen address and clear the screen*/
void init ()
{
    #define mono (int far *)0xb0000000 /*for mono displays...*/
    #define cga  (int far *)0xb8000000 /*...for ega and cga*/
    int mode;

    prevtime = -1; dflag = 1;

    regs.h.ah = 0x0f;
    int86 (0x10, ®s, ®s);
    mode = regs.h.al;
    if (regs.h.ah != 80)               /*fixed to 80 columns*/
         abort ();

    if (mode == 7)
         screen = mono;
    else
         if (mode == 3 || mode == 2)
              screen = cga;
         else
              abort ();
}