Small C ver 1.00 source?

Paul Koning paulkoning at
Tue Jul 14 11:19:44 CDT 2020

> On Jul 14, 2020, at 11:49 AM, Toby Thain via cctalk <cctalk at> wrote:
> On 2020-07-14 11:37 a.m., dwight via cctalk wrote:
>> I'm curious as to where the term P-code came from and what defined it.
>> Dwight
> The first thing that comes to mind is UCSD P-system, but some people
> probably mean it to use "any interpreted bytecode".
> --Toby

I wonder if it came from RSTS-11 BASIC-PLUS (1970).  It used what amounts to P-code, which it called "push-pop code".  Probably because it was pretty much machine code for a simulated stack machine.

That approach is at least a decade older, in fact.  The world's first ALGOL compiler (Dijkstra and Zonneveld, 1961) also used this "machine code for an imaginary machine" technique.  Or more precisely, a hybrid of P-codes and real machine instructions.  This allows your compiler output to use primitives better suited to the language, like "enter ALGOL block" on a machine without a hardware stack.


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