A computer based video/graphics display system includes a computer system having a graphics generator. A video signal from a video source is fed through an input stage to an asynchronous converter. The converter synchronizes the video signal to the graphics generator. The output from the asynchronous converter and the output from the graphics generator are fed to a fading/mixing matrix. The combined signal output from the fading/mixing matrix is fed to a computer display monitor. The display monitor is synchronized to the graphics generator, and the video signal is input asynchronously. Circuitry is provided for displaying at least a portion of the video image together with the graphics image on the display. One or more video images can be manipulated, stored, and displayed in window areas on the display monitor. A picture can be built-up by combining several still images. The system allows the mixing and windowing of computer graphics and one or more video images together on the screen.