OpenVMS I/O

This document provides system programmers with detailed information on interfacing directly with I/O device drivers in the Compaq OpenVMS operating system (Alpha and VAX). It covers the Queue I/O (QIO) interface, ancillary control processes (ACPs), disk drivers, magnetic tape drivers, the mailbox driver, the terminal driver, the pseudoterminal driver, the shadow-set virtual unit driver, the OpenVMS Generic SCSI class driver, and Local Area Network (LAN) device drivers. It also details optional performance features like Fast I/O and Fast Path for OpenVMS Alpha systems, and includes appendices for I/O function codes, status returns, and character sets.