PDP-1 Macro

This document is a technical manual for the MACRO Assembly Program, developed by Digital Equipment Corporation in 1962 for the Programmed Data Processor - 1 (PDP-1) computer.

MACRO is an assembly program designed to simplify computer coding by translating symbolic source programs into executable binary object programs for the PDP-1. It allows programmers to use symbolic names for instruction codes, memory addresses, and parameters, making programs easier to write, read, understand, and relocate within memory.

Key aspects of the document include:

• MACRO Source Language: It details the format of source programs (title, body, start lines), the structure of expressions and syllables, and the use of symbolic addressing, location assignments, and parameter assignments.
• Pseudo-Instructions: These are directives to the assembler itself, governing how the source program is processed (e.g., start, octal, decimal for radix control, character, flexo, text for character storage, repeat for code generation, constants, dimension, variables for automatic storage allocation).
• Macro-Instructions: A powerful feature allowing users to define and reuse sequences of instructions with symbolic parameters (define...terminate), promoting code modularity and efficiency.
• Assembly Process: The program uses a two-pass assembly process: the first pass determines symbolic address values and reserves storage, and the second pass evaluates instructions and generates the binary object program.
• Operation and Control: The manual outlines the steps for operating the MACRO assembler, including source tape format, loading procedures, output generation (binary tapes, symbol tables), test word controls for specific assembly options, and error handling.

In essence, the document provides comprehensive guidance for programmers on using MACRO to write, assemble, and debug programs for the PDP-1, leveraging symbolic programming and advanced assembly features.