C program
#include<conio.h>
#include<dos.h>
#include<stdlib.h>
#include<math.h>
union REGS i, o;
int initmouse()
{
i.x.ax = 0;
int86(0X33, &i, &o);
return ( o.x.ax );
}
void showmouseptr()
{
i.x.ax = 1;
int86(0X33, &i, &o);
}
void hidemopuseptr()
{
i.x.ax = 2;
int86(0X33, &i, &o);
}
void getmousepos(int *x, int *y)
{
i.x.ax = 3;
int86(0X33, &i, &o);
*x = o.x.cx;
*y = o.x.dx;
}
void movemouseptr(int x, int y)
{
i.x.ax = 4;
i.x.cx = x;
i.x.dx = y;
int86(0X33, &i, &o);
}
main()
{
int gd = DETECT, gm, midx, midy, radius, x, y, tempx, tempy;
radius = 100;
initgraph(&gd, &gm, "C:\\TC\\BGI");
if(!initmouse())
{
closegraph();
exit(1);
}
midx = getmaxx()/2;
midy = getmaxy()/2;
showmouseptr();
movemouseptr(midx, midy);
circle(midx, midy, radius);
x = tempx = midx;
y = tempy = midy;
while(!kbhit())
{
getmousepos(&x, &y);
if((pow(x-midx,2)+pow(y-midy,2)-pow(radius,2))>0)
{
movemouseptr(tempx, tempy);
x = tempx;
y = tempy;
}
tempx = x;
tempy = y;
}
closegraph();
return 0;
}