A quasi-composite video signal generator incorporated in a microcomputer having a circuit for generating a quasi-composite video signal to be used to adjust a cathode ray tube (CRT) of a display unit, and the microcomputer being incorporated in the display unit. This generation circuit has a synchronous signal generation section for generating horizontal and vertical synchronous signals, a display setting unit for setting an image to be displayed, and a signal generator for generating a three-state signal Vout according to the image set by the display setting unit and the horizontal and vertical synchronous signals. The signal Vout is converted by a shaping circuit into the quasi-composite video signal, which is applied to drivers of cathode electrodes of the CRT.