ucsd-psystem-vm 0.11


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The ucsd-psystem-vm package is a portable virtual machine for the UCSD p-System.

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About This Project

The ucsd-psystem-vm project is a portable virtual machine (p-code interpreter) for the UCSD p-System. It supports execution of Apple ][ Pascal programs, it can even display TurtleGraphics using X11.

This is a re-packaging of the excellent p-interp program by Mario Klebsch.

Disk Images

In order to do anything useful, the virtual machine needs disk images containing the UCSD p-System operating system files and utilities. You can build your own disk images using the ucsd-psystem-os project, straight from the II.0 sources.

The ucsd-psystem-os project's Download page has a number of links to the sources for different UCSD p-System versions.

Ancient History

The UCSD p-System is a portable operating system that was popular in the early days of personal computers, in the late 1970s and early 1980s.

Like today's Java, it was based on a “virtual machine” with a standard set of low level, machine language like “p-code” instructions that were emulated on different hardware, including the 6502, the 8080, the Z-80, and the PDP-11. In this way, a Pascal 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.

The most popular language for the p-System was UCSD Pascal. In fact, the p-System operating system itself was written in UCSD Pascal, making the entire operating system relatively easy to port between platforms.

By writing a p-code interpreter in the platform's native assembly language, and a few minimal hooks to operating system functions for the file system and interacting with the user, you could move a p-code executable from another system and run it on the new platform. In this way, the p-code generated on one computer could be used to bootstrap the port of the p-System to another computer.

From the Jefferson Computer Museum web site.

See Also

Jefferson Computer Museum
This site has links and history for the UCSD p-System.

Mailing List
This Yahoo! group is devoted to UCSD Pascal.

Search Google
You make like to search Google for more UCSD p-System information.

Sister Projects

UCSD p-System File System: You can mount UCSD p-System disk images as Linux file systems.
UCSD p-System Operating System: The ucsd-psystem-os project contains the II.0 source files (and some bug fixes) plus a Makefile that uses the cross compiler to build the sources, and the file system tools to build working disk images that can be executed using the virtual machine.
UCSD p-System User Manual: A modern reconstruction of the UCSD p-System II.0 User Manual is available as HTML. It includes complete system documentation for the p-machine, file formats, the Pascal dialect supported by the compiler, and more.
UCSD p-System Cross Compiler: You can cross compile your UCSD Pascal code on Unix to create p-Machine object code. By using a cross compiler you can boot-strap a native system by first cross compiling, and then re-compiling with the native compiler.

The ucsd-psystem-vm package is freely distributable under the terms and conditions of the GNU GPL. There is more Software by Peter Miller at his home page.

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