How big is VMS?

This question was asked during my Boot Camp presentation last fall in Boston, and over the past 35 years dozens of times people have asked, how big is VMS? That translates into “how many lines of code are in VMS”? I thought it was time to at least make a stab at pursuing some insight into the answer. I wrote some command procedures to count the number of source lines in.B32,.B64,.C,.MAR,.M64, and.S files. Not counted are blank lines and lines beginning with the standard comment characters and miscellaneous directives for the particular language.
↫ Clair Grant

As always with the ‘lines of code’ metric, there’s some real arbitrariness going on, and in this case that means things like excluding networking, which to me seems like a core part of an operating system, but alas, choices need to be made. The final tally for lines of code, as per the definition used in the article, in the most recent version of OpenVMS, version 9.2-3, is almost 1.9 million. Do with that information as you please.

What’s really fascinating, though, are the deltas between the versions investigated in this article: V6.2 (May 1995, port to Alpha), V7.2 (February 1999, kernel threads, 64-bit APIs, Galaxy, and more), V8.2 (February 2005, port to Itanium), V9.2-3 (december 2024, port to x86). Going from one version to the next, roughly 400000 lines of code were added each time – the article doesn’t theorise about the consistency of this number, and I suspect it’s mostly just a fun coincidence, but it does jump out.