Abstract

A cathode ray tube (CRT) and keyboard display terminal are operated in accordance with the program routines of a microcontroller. The microcontroller includes a random access store which is loadable by the customer during initial program load (IPL) operation to store customer selected program routines for controlling the CRT display and keyboard and for initializing tables in the store which define the customer selected character and symbol set. The tables provide data for determining the functions which are to be performed incident to the depression of each key and since these are customer loadable, the functions can be changed by reinitializing the system. These tables provide the mechanism whereby an operator making use of the keyboard can manually change the functions of each and every key on the keyboard except one key which is dedicated to the function of redefining the functions of other keys. This mechanism permits the operator to manually chain together a large number of functions which will be executed in sequence incident to the depression of a single key which has been selected and redefined to perform all of the desired functions. A redefined key may be returned to its original function by the operator by means of manipulation of the redefine mode key and the key which has been redefined.