Supplementary Program Interface for Visual Display Unit
Original Publication Date: 1986-Jan-01
Included in the Prior Art Database: 2005-Mar-08
A programmable interface is inserted in the data stream between a host computer system and a terminal, to provide supplementary functions to the terminal user. The data stream between the host and the terminal is modified at the interface, but not the data stream protocol. The Supplementary Programmable Interface (SPI) is inserted at a convenient point, close to the Screen and the Keyboard (KB) of a Visual Display Unit (VDU), where the data stream protocol is asynchronous. The data stream protocol is not changed, so that neither end of the cut is aware of the insertion of the SPI. Keystrokes can be issued from the SPI to the host application program, and returned information can be modified by the SPI before it is presented to the User. The SPI can be implemented in the logic of the VDU or by adding a separate microprocessor.