Joel Mc Cormack - P-machine Theory

P-machine Theory

Urs Ammann, a student of Niklaus Wirth, originally presented p-code in his PhD thesis (see Urs Ammann, On Code Generation in a Pascal Compiler, Software—Practice and Experience, Vol. 7, No. 3, 1977, pp. 391–423). The central idea is that a complex software system is coded for a non-existent, fictitious, minimal computer or virtual machine and that computer is realized on specific real hardware with an interpreting computer program that is typically small, simple, and quickly developed. The Pascal programming language had to be re-written for every new computer being acquired, so Ammann proposed writing the system one time to a virtual architecture. The successful academic implementation of Pascal was the UCSD p-System developed by Kenneth Bowles, a professor at UCSD, who began the project of developing a universal Pascal programming environment using the P-machine architecture for the multitude of different computing platforms in use at that time. McCormack was part of a team of undergraduates working on the project. He took this familiarity and experience with him to NCR.