Abstract: A computer system comprises a terminal and a keyboard, the terminal comprises a central control unit for controlling the operation of the keyboard and the keyboard comprises a switch array, the switch array has a plurality of rows and a plurality of columns. The terminal further comprises a data output port for transmitting a command signal from the terminal central control unit and a data input port for receiving a data signal from the keyboard. The command signal comprises a keyboard initialize signal and a keyboard increment signal. The keyboard further comprises a four-wire keyboard interface for communicating with the terminal.

Abstract: An apparatus for interfacing externally generated display data with a display terminal so that the externally generated data can be displayed on the display terminal, the apparatus including means for storing the externally generated display data, means responsive to the display control signals of the display terminal for generating addresses for accessing the storage means, wherein the access addresses are in synchronism with the display control signals, and means for logically combining the internally generated display data and the synchronized externally generated display data.