PURPOSE: To perform window display control over even a CRT display device which has no window display function by securing an area of size as large as lower overlapping data on a memory and saving the data of the lower overlapping part.
CONSTITUTION: A view setting information control part 4 calculates the start line and end line of an overlapping part and requests a free area control part 5 to check whether or not data of the calculated size can be saved or not. The free area control part 5 compares the free size of a free area control table with the calculated size and sends a request to an image plane information retrieval part 8 when the data can be saved. The image plane information retrieval part 8 sends a request for data between a saving start line and a saving end line in the start address of the free area to a CRT display device and when the saving of image plane data is finished, the view setting informa tion control part 4 and free area control part 5 updates a view setting informa tion control table and a free area control table. Consequently, the window display control over even the CRT display device having no window display control circuit becomes possible.
MURATA TOMOAKI
NAGASE HIROMI
MIYAZONO TAKASHI
NEC SOFTWARE KOBE