PURPOSE: To provide the method for displaying a context asynchronous with compressed window image data while matching them when executing window display while expanding and reproducing those data at the work station of a client/server system or the like.

CONSTITUTION: An arbitration program 11 is provided at a client process part 3, when there is the display instruction of a window, the context (such as cursor data and image data under preparation) of a display controller 8 is temporarily saved by a server process part 4 and after the window image data are expansively reproduced and expanded in the frame buffer of the display controller 8, the context is recovered and displayed on the window image while being mixed. On the other hand, when an EXPOSE event is generated, a partial plotting program 12 provided at the client process part 3 executes EXPOSE plotting with the compressed image data as a target.