UCSD P-System

UCSD p-System intro

Ken Bowles and students
UCSD compiler and p-System
UCSD p-System Users Society (USUS)
p-code, p-machine, p-System
Terak and USCD p-System
Western Digital MicroEngine
Apple Pascal II III
Texas Instruments and UCSD
Softech and Pecan
MS-DOS hosted p-System
HP Series 80
Sage and TDI
CP/M and UCSD p-System
UCSD Kermit
Adaptable system
UCSD Yahoo group

Pascal Px compilers were one of the various variants based on the brilliant idea of compiler-interpreter combinations. Started by Wirth in Zurich and perfected in the UCSD P-System. The abstraction delivered by the virtual machine implemented made these systems for the most part hardware independent. And the concept has not lost its value, the Java Virtual Machine with its byte and the .NET ideas are modern variants (and more viable due to the high performance for the money of modern cpu’s!) of the same.

The UCSD P-System (and the popular variant Apple Pascal) extended the idea of compiler-interpreter to a complete and easy to use operating system. All character based and now looking old-fashioned. The UCSD P-System is a brilliant implementation of operating system, utilities and compilers, usable on very limited hardware like the Apple II, all written in a high-level language. The compromise of using a p-code interpreter with a very small memory footprint for programs made it slow but powerful, and easy to run unaltered on different hardware. In fact, Java is identical, bytecode and machine independent. So the idea was not that bad at all!