The present status of microprogramming is developed from Wilkes's initial concept of microprogramming to the more recent bit-slice microprogrammable computer components. This tutorial defines basic concepts and gives a simple example of machine language interpretation. Describing the characteristics of microprogrammed machines provides the background for an examination of microprogrammable bit slice microprocessors, the most significant commercial development since the previous survey paper [3]. The descriptions of recent applications of microprogramming indicate the potential for microprogram use in several areas. A substantial bibliography directs the interested reader to details in many aspects of microprogramming.

The instruction sets of most contemporary, commercially available computers are designed to provide "general purpose" capabilities. In solving specific problems, the instruction sets of these computers often prove to be inefficient. With a dynamically microprogrammable machine this problem can be alleviated by letting the language processor 1) define a set of "machine" instructions better suited for the particular problem at hand and 2) generate the microprograms to interpret the newly defined instruction set.

The concept of microprogramming has been changing with the development of hardware technology to facilitate dynamic microprogramming and the development of software technology to facilitate user microprogramming. An examination of the status of microprogramming systems leads to a discussion of the design and implementation characteristics for both the hardware and software aspects of microprogramming. The concept of microprogrammability is introduced to measure the facility with which a user can microprogram a machine. Discussing and evaluating contemporary machines and software that have been developed to effect user microprogramming reveals a variety of designs and implementations but also indicates directions for future research and development. Describing some of the contemporary applications of microprogramming indicates the potential for exploiting microprogramming in many areas. A comprehensive list of references serves as a guide to details of microprogramming concepts and recent developments.