[1] Vendor SofTech Microsystems[2] emphasized p-System's application portability, with virtual machines for 20 CPUs as of the IBM PC's release.

It predicted that users would be able to use applications they purchased on future computers running p-System;[3] advertisements called it "the Universal Operating System".

Its contribution to these early virtual machines was to extend p-code away from its roots as a compiler intermediate language into a full execution environment.

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

Each hardware platform then only needed a p-code interpreter program written for it to port the entire p-System and all the tools to run on it.

Later, TeleSoft (also located in San Diego) offered an early Ada development environment that used p-code and was therefore able to run on a number of hardware platforms including the Motorola 68000, the System/370, and the Pascal MicroEngine.

UCSD introduced two features that were important improvements on the original Pascal: variable length strings, and "units" of independently compiled code (an idea included into the then-evolving Ada (programming language)).

Project members from this era include Dr Kenneth L Bowles, Mark Allen, Richard Gleaves, Richard Kaufmann, Pete Lawrence, Joel McCormack, Mark Overgaard, Keith Shillington, Roger Sumner, and John Van Zandt.

After SofTech dropped the product, it was picked up by Pecan Systems, a relatively small company formed of p-System users and fans.

Sales revived somewhat, due mostly to Pecan's reasonable pricing structure, but the p-System and UCSD Pascal gradually lost the market to native operating systems and compilers.

Available for the TI-99/4A equipped with p-code card, Commodore CBM 8096, Sage IV, HP 9000, and BBC Micro with 6502 second processor.

The "innovative concept" of the Constellation OS was to run Pascal (interpretively or compiled) and include all common software in the manual, so users could modify as needed.