UCSD P

is a portable operating system that was popular in the late 1970s and early 1980s.

t was based on a "virtual machine" with a standard set of low-level, machine-language-like instructions, the P-Code Machine. P-Code Machines, namely our UCSD P-System were proted to different hardware, including the 6502, the Z-80, the 8086 and 8088 and the PDP-11.

In this way, a compiler that emitted p-code executables could produce a program that could be run under the P-System on an Apple II, a Xerox 820, or a DEC PDP-11 or IBM PC.

Other way round and maybe more correct you could also say a P-System or specifically UCSD P is a specific implementation of the Pascal Language. UCSD P was a specific implementation of the the P-code machine architecture developed by UCSD professor Kenneth Bowles and other personnel including Stephen Franklin and Alfred Bork.

The main and most popular language for the P-System was Pascal. In fact, the UCSD P-System operating system itself was written in UCSD Pascal, making the entire operating system relatively easy to bootstrap onto different HW platforms.

UCSD P was one of the operation or base software systems that was offered for the IBM PC.

It's significance as a high level development system for the PC was killed by Turbo Pascal and the proliferation of C-compilers. When time was ripe for vitual machine based portable development systems, both Pascal and specifically UCSD P where nearly dead as the dodo.

The only relevant survivor, as far as I know, is Delphi*.

THE UCSD P-SYSTEM MUSEUM

And: just to prove that there were other languages than Pascal for the p-System

• which is not quite true as there are still many Pascal compilers around www.ifrance.com