VAX LISP/ULTRIX System Access Programming Guide

This document, "VAX LISP/ULTRIX System Access Programming Guide" (May 1986, Digital Equipment Corporation), provides LISP programmers with the necessary information to interact with the ULTRIX-32 operating system and routines written in other languages.

The guide details three primary system access facilities:

1. Call-Out Facility: Explains how to define and call external routines (written in languages like C) from VAX LISP programs using macros like DEFINE-EXTERNAL-ROUTINE and CALL-OUT. It covers VAX calling conventions, argument passing mechanisms, and automatic data type conversions between LISP and VAX formats.
2. Alien Structures: Describes how to define and manipulate custom data structures (DEFINE-ALIEN-STRUCTURE macro) that map to VAX data types, enabling seamless data exchange between LISP and external routines. This includes creating functions for constructing, accessing fields, copying, and testing these structures.
3. Execution Control and Synchronization: Outlines methods for managing program execution, such as controlling keyboard function interruptions via "interrupt levels," protecting critical code sections from interruption using the CRITICAL-SECTION macro, and synchronizing program flow by pausing execution until a specific event occurs with the WAIT function.

The document is intended for programmers with a solid understanding of both LISP and the ULTRIX-32 operating system's programming interface.