Multi-window display apparatus for managing writing frame memory

Abstract

A multi-window display apparatus has a writing frame memory, a display frame memory, an image transfer portion and a display. The image transfer portion copies window data in a cell to the display frame memory. The display displays the window data copied in the display frame memory. A division table stores data indicating a number of divisions and a maximum size of each cell when the writing frame memory is divided into the specified number of divisions. A status table stores a current number of divisions and a number of cells in use. A cell table stores data indicating, for each cell, an identifier, the size of the window existing in the cell, and the location of the cell in the writing frame memory. A window managing portion responds to a window acquisition request as follows. When the number of cells currently in use is less than the current number of divisions, the window managing portion updates the number of cells used in the status table, selects a vacant cell and updates the size in the cell data table for the selected vacant cell under the condition that a designated size in the window acquisition request is equal to or smaller than the maximum size of the current number of divisions. When the number of cells currently used is not less than the current number of divisions, the window managing portion updates the number of divisions of the status table, updates the number of cells used in the status table, selects a vacant cell and updates the size in the cell data table for the selected vacant cell under the condition that the designated size of the window acquisition request and sizes of all windows already acquired are less than the maximum size of the next largest number of divisions.