What do you mean by retracing? Define horizontal as well as vertical retracing.
Retracing: At the end of each scan line, the electron beam returns to the left side of the screen to begin displaying the next scan line. Horizontal retrace The return to the left of the screen, after refreshing each scan line. Vertical retrace At the end of each frame, the electron beam returns to the top left corner of the screen to begin the next frame.
