[timemachine]

Character Eater:

This TSR program hooks itself with timer interrupt and selects a random row and coloums position at each run and writes space at that position, the person using the computer feels that something is eating up the characters from the screen.

#include"dos.h"
#include<conio.h>
#include<stdlib.h>

//interrupt declarations
void interrupt (*prevtimer)();
void interrupt mytimer();
void writechar(char ch,int row,int col,int attr);

//a far pointer that will access video memory
char far* scr;
int a,b;

//our real program goes from here
void main()
{
scr=(char far*) 0xb8000000;
prevtimer=getvect( 8 );
setvect(8,mytimer);
keep(0,1000);
}

//timer function
void interrupt mytimer()
{
a=random(25);
b=random(80);
writechar(' ',a,b,0);
(*prevtimer)();
}

//function that writes picked up character
void writechar(char ch,int row,int col,int attr)
{
*(scr+row*160+col*2)=ch;
*(scr+row*160+col*2+1)=attr;
}