PURPOSE: To enable the control of an image reader by easily reducing data quantity by a unit that a user can easily understand by recording only a cell where data is judged to exist with the line and column positional information on a recording medium.

CONSTITUTION: Image data is the data having the bit map plane corresponding to 8 lines ×16 columns and image data corresponding to one character is composed of binary data composed of '0' or '1' of 20 bit long x 16 bit broad. This image data is extended to the present VRAM 21 and is displayed on a liquid crystal parcel 19. Successively setting column address information and line address information to '+1' update, whether data exists or not in the cell of the corresponded address location is judged. If data exists, the column address information and the line address information is added to the data of the cell and the data is stored in a floppy disk device 22. Because each cell is stored by adding the line and column address information in the stored image data, the image data i,s easily read, extended and outputted by interpolating null data.