IOCONT Control For IO Programmed Operators

This document is an assembly language listing and documentation for the "IOCONT" subroutine, which provides comprehensive control for I/O (Input/Output) programmed operations. Dated between 1964 and 1965, it details various routines for managing device interaction and data buffering.

Key functionalities include:

1. I/O Buffer Management: Routines such as INBUF and OUTBUF are responsible for setting up and initializing N-buffer rings for input and output devices, defining buffer headers that track current buffer addresses, byte pointers, and item counts.
2. Device Initialization and Assignment: The INIT routine handles the assignment of devices to user channels, the initialization of their I/O status words, and the configuration of job buffer area headers.
3. Operational Control: Dedicated routines manage different stages of I/O operations:
   • CLOSE: Terminates device use, clears input buffer areas, and resets I/O routines to a clear state.
   • IN: Processes input, checks for active devices, manages buffer ring setup, marks buffers as filled, and updates item counts.
   • OUTPUT: Handles output operations, including dump modes, buffer referencing, clearing buffers, and setting item pointers and counts.
   • CALOUT: Dispatches to device service routines to initiate output processes.
4. Device Status and Configuration: Routines like STATO, STATUS, SETSTS, and STATZ provide mechanisms for testing, storing, and setting specific bits within a device's I/O status word.
5. Device Release: The RELEA routine is used to release a device, clearing its assigned bits and associated job numbers.

The document concludes with a detailed symbol table, listing all internal and external symbols used in the program, along with their memory addresses and types, serving as a critical reference for understanding the program's structure and data flow.