Guide to Creating OpenVMS Modular Procedures

This manual provides comprehensive guidelines for advanced system and applications programmers on developing, integrating, and maintaining modular procedures within the OpenVMS AXP and VAX operating environments.

The document covers:

• Introduction and Benefits: Defines modular procedures, explains their advantages such as reusability, reduced development time, improved reliability, and cross-language compatibility. It details how to invoke procedures, utilize procedure libraries (including shareable images), and leverage existing OpenVMS system routines.
• Design Principles: Offers strategies for structuring applications, modules, and files; designing clear procedure interfaces (emphasizing explicit arguments and discouraging implicit ones); managing system resources (stack, heap, and static storage, event flags, logical unit numbers); handling input/output; documenting code; and planning for signaling and condition handling.
• Coding Guidelines: Provides best practices for naming conventions (facilities, procedures, files, modules, PSECTs, status codes), initializing modular procedures effectively, and writing Asynchronous System Trap (AST)-reentrant code to ensure robust operation in interrupt-driven contexts, including techniques to prevent race conditions and deadlocks.
• Testing Methodologies: Outlines detailed approaches for unit testing (black box and white box), ensuring language independence, and performing integration testing (advocating incremental over all-at-once). It also describes methods for verifying reentrancy and analyzing performance.
• Integration and Maintenance: Instructs on creating facility prefixes, object module libraries, and shareable image libraries. It addresses critical maintenance aspects like ensuring upward compatibility for future updates and implementing regression testing.
• Summary: Includes an appendix summarizing all modular programming guidelines for quick reference.

Overall, the manual serves as a guide for building well-structured, efficient, and maintainable applications on OpenVMS by adhering to established modular programming standards.