IOCSS IO Common System Subroutines

This document is a technical reference detailing various Input/Output (IO) and common system subroutines for a DEC (Digital Equipment Corporation) computer system, likely from the mid-1960s. It provides assembly-level listings, descriptions, and operational details for each routine.

The document covers the following key functionalities:

1. Buffer Management (ADVBFE, ADVBFF, BUFCLC, BUFCLR, CLRBYT): Routines for advancing buffer addresses, managing buffer usage flags, setting up buffer rings, and clearing buffer contents.
2. ASCII and Data Handling (ASCIA, SETBYT): Functions for performing arithmetic operations on ASCII numbers and setting byte size parameters based on data modes (e.g., Binary, Image, ASCII Packed).
3. Device Assignment and Management (ASSIN, ASSASG, IORELS, IOALL, IOKILL): Subroutines for searching and assigning devices to jobs, releasing devices, and initiating IO operations for all assigned devices.
4. Interrupt and System Service (IOSET, UINTQ): Routines for handling device-related operations from an interrupt service routine and processing UUO (User Unallocated Output) calls.
5. Item and Count Management (ITMSET, ITMCNT, ITMCT1): Functions to calculate and set item counts based on buffer, word, and byte sizes.
6. Data Storage and Checksum (STODAT, STOSQD, CKS12): Routines for storing data items into buffers, performing checks based on data modes, and calculating folded 12-bit checksums for data integrity.
7. Device Status (SETIOS): A routine to set and validate device status words.

Each subroutine entry typically includes its calling sequence, exit conditions, monitor interface details (storage, symbols, accumulators used), and a detailed assembly code listing with comments. The document concludes with a comprehensive symbol table, listing all internal and external symbols with their memory addresses and types. This serves as a vital low-level programming guide for interacting with the system's IO and common services.