Multi-window control system

Claim 1

In a multi-window control system, which is provided with at least one terminal having a multi-window display, said at least one terminal being connected, through a terminal controller, to a plurality of processors including a first processor and a second processor having a priority higher than that of said first processor, wherein messages coming from said first processor and messages coming from said second processor are displayed under control of said terminal controller, the improvement, wherein said terminal controller comprises: control means for controlling internal operation of the terminal controller; first holding means for holding a first terminal address of a first terminal, which is to display a first message coming from the first processor, and a first virtual screen buffer address of a virtual screen buffer in said first terminal; second holding means for holding a second terminal address of a predetermined terminal which is to display a second message coming from the second processor; first comparing means, coupled to said first and second holding means and said control means, for comparing said first terminal address with said second terminal address when a message coming in from said processor is received by said memory means for storing indicators for state of use a plurality of virtual screen buffers in said predetermined terminal; selection means, coupled to said memory means, for selecting one of said plurality of virtual screen buffers in response to said state of use indicators; save buffer means, coupled to said plurality of virtual screen buffers, for saving a content of said one of said plurality of virtual screen buffers selected by said selection means; update means, coupled to said memory means, for updating said state of use indicators; and switching means, coupled to said plurality of virtual screen buffers, said first processor and said save buffer means, for switching said first message between said first processor, and a selected one of said save buffer means and said plurality of virtual screen buffers, wherein said switching means, said update means, and said selection means are responsive to said control means.