SYSTEM, METHOD AND PROGRAM FOR PROTECTING INFORMATION ON COMPUTER SCREEN

Whenever a drawing command is executed, a computer system having a graphic user interface such as a multi-window system determines, from the logical operation pattern of the drawing command, what kind of information is inherited by a drawing result from the drawing command, preferably without performing a complicated step such as an image process. At the same time, the computer system controls information flow of an image outputted to a screen by managing labeled area maps which correspond one to one to images on the screen and in a memory.