Abstract: A method for moving a cursor (14) back one space on a display screen by a second, same character key stroke at a keyboard, comprising the steps of: catching and storing a key information (16) when a key is stroked at the keyboard; selecting a character information from each key stroke; comparing key information (16) including a character information (10) in a storage area with a next key information (18) including a next character information (12), immediately following key information (16); and moving cursor (14) back one space on the display if both key information (16) and next key information (18) are the same.

Abstract: There is disclosed a system for detecting a difference between an image on a primary sheet and an image on a secondary sheet. A microprocessor unit determines whether corresponding ones of first and second image elements representative respectively of the images on the primary and secondary films differ in optical density from each other below a predetermined level. The two corresponding first and second image elements different above the predetermined level are emphasized in optical density difference and alternately displayed on a display screen at a short time interval, so that the dot of the display screen which alternately display these image elements is caused to flicker.