Multiprogramming System Manual

This document describes the PDP-6 Multiprogramming Time-Sharing System, detailing its integrated hardware and software designed for simultaneous multi-user access via consoles. The system aims for simplicity, modularity, and open-endedness, supporting diverse tasks including programming, data conversion, batch processing, and real-time applications.

The system evolves through four stages, from basic multi-programming (System I) to configurations incorporating drum (System II), disc and magnetic tape (System III) for backup storage and program swapping, and eventually additional processors for enhanced computation (System IV). Hardware support includes executive-user mode for memory protection, large core memory with fast auxiliary file storage (drums, discs, Dectapes), ASCII data representation, and a 7-level priority interrupt system for concurrent I/O.

At its core, the Software Monitor manages resources, schedules jobs, and handles user interactions. It allocates facilities, processes console commands, and coordinates I/O operations through device-independent routines, using a round-robin scheduling algorithm to ensure fair resource distribution. User programs run in protected memory areas, with system safeguards against interference.

Key utilities and components include:

• Console Commands: A comprehensive set of commands allows users to initialize, manage, and terminate jobs, allocate core, load/save programs, and assign I/O devices.
• Input/Output (I/O) System: Provides device-independent I/O operations with various data modes (ASCII, Binary, Dump, Image) and uses a ring buffer structure for data transfer.
• The Loader: Loads and links relocatable binary programs, builds symbol tables for debugging, and generates storage maps.
• The Editor: A Dectape-based utility for creating, modifying, and resequencing text files.
• The Peripheral Interchange Program (PIP): A versatile program for transferring and performing simple editing on data between different I/O media.
• The Batch Control Program (BCP): Processes job streams from cards or tapes, interpreting console-like commands without direct user interaction.

The document also provides details on executive components, memory allocation, and device characteristics.