This is a super minor correction on my part, but this is a weird phrasing because "the ACM" is a huge organization that publishes proceedings for a great range of interests --- it isn't a venue in itself. The name of the venue you're looking to reference is Communications of the ACM, more commonly just referred to as Communications or CACM.
As an aside, Communications is a sort of unique venue for publication. The submissions are peer-reviewed, but the nature of the submissions is more similar to a blog post or editorial article than traditional papers you'll find in other proceedings from conferences and journals (and, indeed, the ACM refers to CACM as a "magazine"). It makes for good "fun" reading!
The vibe of CACM also has changed significantly over the decades it's been around. When it started in the late 1950s, and through the mid 90s, it was really a "Journal of the ACM"-lite; the research articles were quite good! Then it morphed into a trade magazine and, by the late 2000's, it was kind of an embarrassment.
To Vardi's credit (the previous CACM EIC), CACM clawed back some of its technical chops in the 2010s. I wouldn't claim it's near the quality of 1970s CACM, but it actually has technical content in it again. Equations, even, gasp!
Yes, the CACM along with all of the SIG* journals. TBH I gave up my membership when the ACM seemed more of a money grab and less about computing.
You are correct, and I'll deny having a 1978 copy of the SIGPLAN (Programming Languages) Conference docs on the history of some of the languages that were popular then. :-)
SIGPLAN is my only ACM membership; I figure I can support my primary publishing organization at $25/year or whatever. So your 1978 issue sounds like a pretty cool piece of history to have to me!
Some of the same articles, but with updates and added reader comments.
(I posted Amazon, but there is a ton on the used market)