Christopher J Martin

Chris Here - found this post 3 years later. The WAIT statement is for the vertical retrace to occur. It allows you to wait until the beam is not drawing active screen to update the page data from one image to the other. The images themselves are interlaced in light and dark bands so that both images have an overall similar brightness and that is why it reduces the apparent flicker even on non-CRT although it works absolutely the best on an old RGB CGA TTL Monitor.