c program which restricts the movement of pointer

void main()
{
union REGS k,o;
//show mouse pointer
k.x.ax=1;
int86(0x33,&k,&o);
//x coordinate restriction
k.x.ax=7;
k.x.cx=20;
k.x.dx=300;
int86(0x33,&k,&o);
//y coordinate restriction
k.x.ax=8;
k.x.cx=50;
k.x.dx=250;
int86(0x33,&k,&o);
getch();
}