TOPS-20 Monitor Calls Reference Manual

This document is a technical reference manual for monitor calls in the TOPS-20 operating system, updated as of December 1982. It is intended for assembly language programmers already familiar with the operating system.

The manual is organized into three chapters:

• Chapter 1 (Introduction): Describes calling conventions, monitor call arguments (addresses, page/section numbers, byte pointers, file/process handles, etc.), error processing, and general documentation conventions.
• Chapter 2 (Functional Organization of JSYS's): Explains how monitor calls are organized by function, covering accounting, referencing files (including JFNs and directory access), communicating with devices (line printers, terminals, magnetic tape, etc.), software interrupts, process capabilities, and date/time conversions.
• Chapter 3 (TOPS-20 Monitor Calls): Provides an alphabetical reference of individual monitor calls. Each entry includes a brief description, calling sequence (accepts/returns), and a list of possible error mnemonics.

The document also includes appendices for collating sequences (ASCII, SIXBIT, EBCDIC) and symbol definitions (MONSYM, MACSYM, ACTSYM). The manual concludes with a detailed index and a "Reader's Comments" form for user feedback.