The UCSD p-System, developed at The University of California, San Diego, was a self-compiling and self-hosted operating system based on p-code optimized for generation by the Pascal programming language.

Like many other p-code machines, the UCSD p-Machine is a stack machine, which means that most instructions take their operands from the stack, and place results back on the stack.

UCSD Pascal was based on a p-code machine architecture.

UCSD p-System achieved machine independence by defining a virtual machine, called the p-Machine ( or pseudo-machine, which many users began to call the " Pascal-machine " like the OS — although UCSD documentation always used " pseudo-machine ") with its own instruction set called p-code ( or pseudo-code ).

Urs Ammann, a student of Niklaus Wirth, originally presented a p-code in his PhD thesis, from which the UCSD implementation was derived, the Zurich Pascal-P implementation.

There were four versions of UCSD p-code engine, each with several revisions of the p-System and UCSD Pascal.

* ucsd-psystem-vm, a portable virtual machine for UCSD p-System p-code

The speed of these COM executable files was a revelation for developers whose only prior experience programming microcomputers was with interpreted BASIC or UCSD Pascal, which compiled to p-code.

Gosling traces the origins of the approach to his early 1980s graduate student days, when he created a pseudo-code ( p-code ) virtual machine for the lab's DEC VAX computer so that his professor could run programs written in UCSD Pascal.

* p-code of UCSD Pascal implementation of the Pascal programming language

This idea originated as early as in the late 1970s, when the UCSD Pascal system was developed to produce and interpret p-code.

JRT was a Pascal interpreter, that compiled down to its own pseudo-code totally separate from UCSD Pascal p-code.

There are many historical examples of code running on virtual machines, such as the language UCSD Pascal using p-code, and the operating system Inferno from Bell Labs using the Dis virtual machine.

Also available for programming the HP 9800 series was a bootable development environment based on UCSD Pascal, but with a compiler which would generate fast, native Motorola 68000 object code, instead of the slower p-code typical of most UCSD Pascal implementations.

Crick died of colon cancer on 28 July 2004 at the University of California San Diego ( UCSD ) Thornton Hospital in La Jolla ; he was cremated and his ashes were scattered into the Pacific Ocean.

Robinson gave the novella in rough form to Ursula K. Le Guin to read and edit while he was enrolled in her writing workshop at UCSD in the spring of 1977.

In the early 1980s, UCSD Pascal was ported to the Apple II and Apple III computers to provide a structured alternative to the BASIC interpreters that came with the machines.

When the original IBM-PC was created in 1980, there were three leading competing operating systems: PC-DOS, CP / M-86, and UCSD p-System, while Xenix was added in 1983-1984.

The San Diego campus was founded as a marine station in 1912 and became UCSD in 1959.

UCSD Pascal was a Pascal programming language system that ran on the UCSD p-System, a portable, highly machine-independent operating system.

UCSD Pascal was first released in 1978.

It was developed at the University of California, San Diego ( UCSD ).

UCSD Pascal was developed at The University of California, San Diego Institute for Information Systems in 1978 to provide students with a common operating system that could run on any of the then available microcomputers as well as campus DEC PDP-11 minicomputers.

UCSD p-System ( Version IV, supplied by SofTech ) was one of three operating systems ( along with PC-DOS and CP / M-86 ) that IBM offered for its original IBM PC ; but the p-System never sold very well for the IBM PC, mainly because of a lack of applications and because it was more expensive than the other choices.

The UCSD Pascal p-Machine was optimized for the new small microcomputers with addressing restricted to 16-bit ( only 64KB of memory ).

The UCSD Pascal compiler was distributed as part of a portable operating system, the p-System.

The Pascal dialect of UCSD Pascal came from the subset of Pascal implemented in Pascal-P2, which was not designed to be a full implementation of the language, but rather " the minimum subset that would self-compile ", to fit its function as a bootstrap kit for Pascal compilers.

Somewhat in the fashion of UCSD Pascal it was implemented via ' compilation ' into an intermediate representation.

It was also the basis for programming classes taught by Jef and Jon in the UCSD Visual Arts Dept.

He later hired his former student Bill Atkinson from UCSD to work at Apple, along with Andy Hertzfeld and Burrell Smith from the Apple Service Department, which was located in the same building as the Publications Department.

Java came to be used for server-side programming, and bytecode virtual machines became popular again in commercial settings with their promise of " Write once, run anywhere " ( UCSD Pascal had been popular for a time in the early 1980s ).

Previously, IBM had offered the UCSD p-System as an option for Displaywriter, an 8086-based dedicated word processing machine ( not to be confused with IBM's DisplayWrite word processing software.

Some intrinsics were provided to accelerate string processing ( e. g. scanning in an array for a particular search pattern ); other language extensions were provided to allow the UCSD p-System to be self-compiling and self-hosted.

UCSD p-System began around 1974 as the idea of UCSD's Kenneth Bowles, who believed that the number of new computing platforms coming out at the time would make it difficult for new programming languages to gain acceptance.

*, UCSD has released portions of the p-System written before June 1, 1979 for non-commercial use.

* ucsd-psystem-os, cross-compilable source code for the UCSD p-System version II. 0

* UCSD P-System at Pascal for Small Machines

When Steve Wozniak developed the first disk drives for the Apple II, Raskin went back to his contacts at UCSD and encouraged them to port the UCSD P-System operating system ( incorporating a version of the Pascal programming language ) to it, which Apple later licensed and shipped as Apple Pascal.

CP / M-86 was released a few months after the PC and was one of three operating systems available for purchase from IBM, PC DOS, CP / M-86 and UCSD Pascal.

The first five games in the series were written in Apple Pascal, an implementation of UCSD Pascal, and were ported to many different platforms by writing UCSD Pascal implementations for the target machines ( Mac II cross-development ).

At UCSD, Norman was a founder of the Institute for Cognitive Science and one of the organizers of the Cognitive Science Society ( along with Roger Schank, Allan Collins, and others ), which held its first meeting at the UCSD campus in 1979.