PDP-6 Time Sharing Software

This document outlines the Digital Equipment Corporation's PDP-6 time-sharing system, an integrated hardware-software solution designed to reduce computation costs and improve program turnaround time by enabling the concurrent operation of multiple user programs.

At its core is the PDP-6 Monitor, a comprehensive control program that schedules multi-user time-sharing, allocates system resources (memory, I/O devices), manages all system input/output, and protects/relocates user programs. It employs time-slicing and hardware features to prevent interference between jobs and optimizes I/O by switching between programs when one is waiting for I/O completion.

The document details several key software components and their functionalities:

• Monitor Commands: Fundamental commands for job initialization, status display, termination, core and device assignment, program loading/saving, execution control, and debugging.
• DECtape Editor: A tool for creating, modifying, and managing text files (including source code for compilers/assemblers) on DECtape, streamlining the editing process.
• FORTRAN II Compiler: A one-pass compiler featuring extended language capabilities, translating FORTRAN programs into optimized machine code, and supporting flexible I/O and dynamic device assignment.
• MACRO-6 Assembler: A sophisticated two-pass assembler with complete MACRO facilities, translating symbolic instruction codes into machine language compatible with the Linking Loader and DDT-6.
• The Linking Loader: Automatically loads and relocates compiled/assembled programs into memory, offering options for storage maps, symbol tables for debugging, and library searches.
• Dynamic Debugging Technique (DDT-6): An on-line symbolic debugging system that allows users to monitor, modify (instructions/data), and control program execution (e.g., setting breakpoints, restarting) in real-time, significantly enhancing debugging efficiency.
• Peripheral Interchange Program (PIP): Manages I/O transfers and data conversions between various PDP-6 peripherals, operating concurrently with other jobs and supporting diverse data formats and sequencing.
• FORTRAN Operating System and Library: The runtime environment for FORTRAN programs, handling I/O and providing a rich library of arithmetic, utility, and I/O conversion functions.

The document emphasizes the system's user-friendliness, dynamic interaction, and efficiency for both on-line interaction and batch job processing, illustrating its features with command examples and system diagrams.