permacomputing

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Author: neau <neau@web>
Date:   Wed, 22 Jun 2022 16:03:44 +0200

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+In computer programming, a p-code machine is a [[virtual machine]] designed to execute the assembly language of a hypothetical CPU.
+
+Niklaus Wirth specified a simple p-code machine in the 1976 book Algorithms + Data Structures = Programs. The machine had 3 registers - a program counter p, a base register b, and a top-of-stack register t. There were 8 instructions:
+
+    lit 0, a  : load constant a
+    opr 0, a  : execute operation a (13 operations: RETURN, 5 math functions, and 7 comparison functions)
+    lod l, a  : load variable l,a
+    sto l, a  : store variable l,a
+    cal l, a  : call procedure a at level l
+    int 0, a  : increment t-register by a
+    jmp 0, a  : jump to a
+    jpc 0, a  : jump conditional to a[6]
+
+See more:
+
+* [On Wikipedia](https://en.wikipedia.org/wiki/P-code_machine)