Allegro Programming Tutorial, by Richard G Baldwin

Draw the ball in the new location

After the code in the switch statement finishes executing:

We need to erase the current image of the green ball and
Draw a new image of the ball in the same or a new location. (Same if against the wall.)

That is accomplished by the code in Listing 5.

Listing 5. Draw the ball in the new location.

  acquire_screen();
  circlefill (screen,tempX,tempY,radius,makecol(0,0,0));
  circlefill (screen,x,y,radius,makecol( 128, 255, 0));
  release_screen();

  rest(5);//Delay for five milliseconds
}// end moveBall function.