M-1149 MACRO May62

This document is an outline of the PDP-1 Macro Assembly Program, developed at MIT in 1962, intended as an interim guide for users. It describes Macro as a two-pass assembly system: Pass 1 assigns symbols and allocates storage, and Pass 2 translates the Macro language into a binary program tape for execution.

The memo details the Macro language, including its character set, symbols (numbers, values, pseudo-instructions), syllables, and words. Key features of the language include pseudo-instructions for memory allocation (constants, variables, dimension), character input (flexo, char, text), code repetition (repeat), and the ability to define and call custom "Macro instructions" using dummy symbols for parameters.

Operational instructions cover the two-pass assembly process from English tape input to binary tape output, including handling multiple tapes, the format of the English tape, and utilities for managing and printing symbol/Macro definition tables. It also describes test word controls for advanced operations and lists error messages encountered during assembly.