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

typedef unsigned char byte;

int pushed, released, count, myQuit;
char mykey, mykey2;

void interrupt (*OldClockHandler)(void);
void interrupt (*OldProcessKey)(void);

void interrupt CountClock(void) {
  if (pushed==1) { count++; }
};


void interrupt ProcessKey(void) {

  asm {
    in al,60h;
    mov mykey,al;
  }

  pushed=1;

  if ((mykey2+0x80)==mykey) { pushed=0; released=1; }
  mykey2=mykey;

  OldProcessKey();
}

void main() {

  OldClockHandler = getvect(0x1c);
  setvect(0x1c, CountClock);
  OldProcessKey = getvect(0x9);
  setvect(0x9, ProcessKey);

  count=pushed=released=myQuit=0;

  clrscr();

  do {
    if ((released==1)) {
      gotoxy(1,1);
      printf("Delka stisku klavesy: %d ms    ", count*55);
      count=0;
      released=0; pushed=0;
    }
    if (kbhit()) { if (getch()==27) myQuit=1; }
  } while (!myQuit);

  setvect(0x1c, OldClockHandler);
  setvect(0x9, OldProcessKey);
}