Algebra - Program for Manipulating Expressions

This document describes ALGEBRA, a program developed by P. J. Brown and R. C. Saunders at the University of Kent, dated July 21, 1972, and written in PAL-11.

ALGEBRA is designed for manipulating logical expressions. It allows users to:

• Declare a set of values (e.g., TRUE, FALSE).
• Define operators (specifying if they are unary or binary, their precedence, and their behavior for all possible value combinations).
• Evaluate complex expressions involving these user-defined values, operators, and variables.

The program supports various statements for interaction, including:

• OPERATOR: To define or redefine operators.
• TABLE: To generate truth tables for expressions, enumerating results for all variable combinations.
• TRY: To test if an expression consistently evaluates to a single value or is a "contingency" (depends on variable values).

This specific version runs on a PDP-11/20 under DOS (Disk Operating System). It offers flexible input/output handling through command strings, a significant improvement over an earlier "stand-alone" teletype-only version. The development of ALGEBRA was part of research into implementing machine-independent software using the ML/I macro processor. The document also details program entry, exit, error handling, and various commands for controlling the program session.