In a microcomputer internally comprising a circuit including a CPU and operating in synchronism with an internal clock signal, and an OSD controller operating in synchronism with the internal clock signal and an external horizontal synchronous signal, an oscillation circuit is coupled to an external oscillator, for generating the internal clock signal used in common to the circuit and the OSD controller. An oscillation control circuitry receives the horizontal synchronous signal for generating a CPU stop request signal to the circuit before supply of each horizontal synchronous signal, so that the circuit generates a CPU stop signal after a stopping processing is completed. When the oscillation control circuitry receives the CPU stop signal, the oscillation control circuitry causes the oscillation circuit to stop generation of the internal clock signal. Thereafter, in response to each horizontal synchronous signal, the oscillation control circuitry causes the oscillation circuit to restart the generation of the internal clock signal. As a result, the internal clock signal is generated in synchronism with the horizontal synchronous signal.

A word processing system is provided with printing means for printing on a character by character basis a data stream including merged graphic and alphanumeric data. The word processing system is provided with an interactive display for displaying by character generation a data stream representative of alphanumeric characters to be printed together with means for printing the characters on a document on a character by character basis. Operator interactive apparatus is provided whereby the operator can form a graphics data stream which is displayable on said display by character generation. This graphics data stream may then be integrated into the existing alphanumeric data stream, and the data in this integrated data stream may then be applied to the printing means whereby the alphanumeric characters and the graphic characters represented by this data stream are printed character by character to provide a document having the integrated alphanumeric and graphic information.

A video signal generating circuit comprises a buffer memory for storing character codes and control data for control of vertical character positions, a character pattern memory having a plurality of stored character patterns which are selected by the output of the buffer memory, and a control circuit for successively reading the character codes and control data from the buffer memory and the character patterns from the character pattern memory. The value of a logical operation of raster data generated by the control circuit and the control data is used as raster data or an effective raster scan signal for the character pattern memory.

A video display terminal is disclosed for use in displaying images of data characters on a display screen. Multibit coded data words are supplied by a data source, such as a memory, to a character generator circuit which controls the display of data characters on the face of a video display screen. Character codes are used to address a dot pattern memory which stores dot patterns to provide an image of the required data character to be displayed. The dot patterns may be stored on one size matrix in the dot pattern memory, such as in a 9.times.9 cell, and displayed on a larger dot matrix, such as 9.times.16, on the display screen. Subscripts or descending characters may be stored in the dot pattern memory and vertically repositioned when displayed on the screen. Means are also provided for adjusting the vertical positioning of a line of characters.

An image processing system has an original reader or an image file for generating an image signal, a soft display, a high-speed printer, a small printer, a work station with a CPU, and a switching device. An image can always be displayed or printed at the center of a display surface or of a recording medium irrespective of a difference in the image and the display surface or recording medium.