The IBM S/360 family of computers -- are well worth studying for any serious student of computer history: https://en.wikipedia.org/wiki/IBM_System/360 https://

The IBM S/360 family of computers -- are well worth studying for any serious student of computer history: https://en.wikipedia.org/wiki/IBM_System/360 https://en.wikipedia.org/wiki/IBM_System/360 >"The slowest System/360 model announced in 1964, the Model 30, could perform up to 34,500 instructions per second, with memory from 8 to 64 KB.[3] High-performance models came later. The 1967 IBM System/360 Model 91 could execute up to 16.6 million instructions per second.[4] The larger 360 models could have up to 8 MB of main memory,[5] though that much memory was unusual; a large installation might have as little as 256 KB of main storage, but 512 KB, 768 KB or 1024 KB was more common. Up to 8 megabytes of slower (8 microsecond) Large Capacity Storage (LCS) was also available for some models." But -- Even if someone had the full 8 Megabytes (8MB, not 8GB or 8TB!) back in the 1960's (which would have been the exception, rather than the norm!) -- that still would not be enough to shoehorn a modern-day Linux kernel into it, much less also gcc, glibc, libraries, Node.js, npm, Python, and whatever other programs, libraries or software components are being used for someone's tech stack... Whether a virtual machine was running in the background -- or not... In the 1980's and 1990's, while corporate Mainframes may have had hardware support for virtualization -- consumer x86 PC's most certainly did not. Thus, if someone was running MS-DOS directly on an x86 PC of that era without Windows, they were effectively running on "bare metal" -- because MS-DOS didn't trap and proxy and reroute x86 IN / OUT instructions (or DMA for that matter) -- assembler programmers of this era using an assembler under DOS had full access to ALL of the underlying hardware in their PC's... Still, you make an excellent point that modern VM's, as programs, have historic ancestors that existed in the mainframe computer world as far back as the 1960's -- most notably as CMS on the IBM S/360 mainframe family.