REC/8: A CONVERT Compiler of REC for the PDP-8

Abstract

REC/8 is a CONVERT program, realized in the CTSS LISP of Project MAC, for compiling RED expressions into the machine language of the PDP-8 computer. Since the compilation consists in its majority of subroutines calls (to be compiled, after removal of LISP parentheses by MACPO-8) the technique is applicable with trivial modification to any other computer having the subroutine jump and indirect transfer instructions. The purpose of the program is both to compile REC expressions and to illustrate the workings of the REC language, and accordingly a description of this language is given. It contains operators and predicates; flow of control is achieved by parentheses which define subexpressions, colon which implies interaction, and semicolon which terminates the execution of an expression. Predicates pass control to the position following the next colon or semicolon, allowing the execution of alternative expression strings.