VMS is like a nightmare about RSX-11M.

A sense of déjà vu washed over many a system administrator as they booted up their VMS systems, only to be reminded of the quirks and eccentricities of its spiritual predecessor, RSX-11M. For those who cut their teeth on the older operating system, the similarities between VMS and RSX-11M are more than just superficial - they evoke a strong sense of nostalgia, mixed with a dash of frustration. Like a bad dream that refuses to shake, VMS conjures up memories of late nights spent wrestling with RSX-11M's idiosyncrasies, from its terse command-line interface to its finicky device drivers.

Developed by Digital Equipment Corporation (DEC), VMS was first released in 1977 as a multi-user, multiprocessing operating system for the company's new VAX-11/780 minicomputer. Meanwhile, RSX-11M, launched in 1973, was a high-performance operating system for DEC's PDP-11 minicomputer family. Although VMS was designed to be a more modern and capable successor, it inherited many of RSX-11M's design philosophies and command structures. This heritage is evident in VMS's command-line interface, which, despite being more comprehensive, still bears the imprint of RSX-11M's concise, if sometimes cryptic, syntax.

One of the most striking similarities between the two operating systems is their use of a layered approach to process management. Both VMS and RSX-11M employ a hierarchical model, where processes are organized into a tree-like structure, with parent processes spawning child processes to perform specific tasks. While this design allows for efficient resource allocation and job control, it can also lead to complexity and confusion, particularly when dealing with error handling and process synchronization. Those familiar with RSX-11M's process management will find themselves navigating similar challenges in VMS, often with the same sense of trepidation.

Furthermore, VMS's file system, while more advanced than RSX-11M's in many respects, still retains some of the same fundamental characteristics. Both operating systems use a file system that is based on a hierarchical directory structure, with support for file versioning and access control. While VMS's file system is more flexible and scalable, it can still be temperamental, particularly when dealing with large numbers of files or complex directory hierarchies.

In many ways, VMS can be seen as a polished, more capable version of RSX-11M, with many of the same strengths and weaknesses. While it has evolved to support modern computing environments and hardware architectures, its underlying design and philosophy remain rooted in the traditions of its predecessor. For those who have experienced the trials and tribulations of RSX-11M, using VMS can be a bit like reliving a bad dream - but one that is, perhaps, a little more manageable, and a little more refined. Despite the initial sense of déjà vu, VMS has proven itself to be a robust and reliable operating system, capable of supporting demanding applications and workloads.