#include "dos.h"

void interrupt myfunc();

void interrupt (*prev)();

int ticks;

char far *vdu=(char far*)0xb8000000l;

main()

{

//AIM : screen display goes hazy every 3 seconds.

unsigned long far *clkint;

clkint=(unsigned long far *)32;

prev=(void (interrupt far*)())*clkint;

*clkint=(unsigned long)myfunc;

keep(0,500);

return 0;

}

void interrupt myfunc()

{

int i,j;

ticks++;

if (ticks==182/4)

{

for(j=0;j<14000;j++);

for(i=0;i<3999;i+=2)

{

if(*(vdu+i) >= 'A' && *(vdu+i) <= 'Z')

*(vdu+i)+=32;

else

{

if(*(vdu+i) >= 'a' && *(vdu+i) <= 'z')

*(vdu+i)-=32;

}//if else

}//for

ticks=0;

}//if

(*prev)();

}