Monitors Programmer's Reference Manual Advanced Software System

This document serves as a comprehensive programmer's reference manual for the PDP-9 ADVANCED Software System, detailing the architecture and operation of its two primary monitor systems: the Input/Output (I/O) Monitor for paper tape-based systems and the more sophisticated Keyboard Monitor for systems with bulk auxiliary storage.

The manual outlines the hardware requirements for both monitors and introduces the suite of system programs available, including FORTRAN IV, the MACRO-9 Assembler, DDT-9 Debugging System, EDIT-9 Text Editor, PIP-9 Peripheral Interchange Program, and the Linking Loader. It describes the Input/Output Programming System (IOPS), which handles I/O functions and device interaction, relieving programmers of low-level device control.

Key programming concepts are covered in detail, such as data modes (IOPS ASCII, binary, image, dump), the structure and utilization of line buffers for data transmission, and device assignment tables (.DAT) for mapping logical I/O units to physical hardware. The document provides a comprehensive list of user program commands (macros like .INIT, .READ, .WRITE, .SEEK, .CLOSE), explaining their syntax, purpose, and effects.

For system operation, the manual describes loading procedures for system and user programs under both monitors, detailing command strings, options, and error handling for various utilities. It also includes an extensive summary of Keyboard Monitor commands for system information, dynamic device assignment, and program execution control. Furthermore, it discusses programming for device independence, outlines standard I/O handler features, and explains the interaction between software levels and hardware interrupts, including API channel assignments and error detection mechanisms.