Issue No. 12 - Dec. (1974 vol. 7)
Stephen Y. H. Su , The City College, City University of New York
A digital system can be described at several levels. 1) The highest level is the algorithmic level which specifies only the algorithm to be used for solving a design problem. 2) The second level is the PMS (Processor, Memory, Switch) level which describes a system by processors, memory components, peripheral units, and switching networks. 3) The instruction level describes the instructions of a computer. 4) The register transfer or microinstruction level describes operations among registers. 5) The logic level expresses network in terms of gates and flip-flops. 6) The lowest level is the circuit level which implements gates and flip-flops by circuit elements such as transistors, resistors, etc.
S. Y. Su, "A survey of computer hardware description languages in the U.S.A.," in Computer, vol. 7, no. , pp. 45-51, 1974.