Introduction

THE term microprogramming has come to mean many things to many people. Its original meaning was given by M. V. Wilkes in 1951 [1], [2]. Wilkes used a technique of structuring the control of a digital computer which simplified its design and implementation. This technique was called microprogramming because it provided an algorithmic method of defining the microscopic state of a machine. It soon became apparent that microprogramming allowed a designer to delay decisions about the instruction set to be supported until after the microprogrammable hardware was nearly completed. Design errors could be corrected easily by inexpensive changes in the microprogram, rather than expensive changes in the hardware.