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Was any operating system actually able to go from single-user to multi-user so easily? Windows NT and OS X were totally rewritten from the ground up relative to

Was any operating system actually able to go from single-user to multi-user so easily? Windows NT and OS X were totally rewritten from the ground up relative to their single-user predecessors Windows 9x and classic Mac OS.

hypercube33 2y ago
NT is closer to a mainframe OS than 9x and it came out in the win3 era
- kbolino 2y ago
  Yeah, I actually used NT 3.51 for some time. However it was the NT line that replaced the 9x line, at least from the consumer perspective.
nullindividual 2y ago
NT had no predecessor (at least from Microsoft; architecturally it's predecessor would be VMS). It was ground-up multi-user. Mac OS [Classic] was not OS X's predecessor, either -- it was NeXTStep.
- kbolino 2y ago
  You are right on the technical lineage, but I was referring to how these products were (ultimately) presented commercially. The facts that they are both older than one might think and they were developed with specific goals from the start I think more clearly illustrate that you can't just "bolt on" such fundamental differences.
fasa99 2y ago
yea, a big one. Once there was an intentionally multi-user-from-ground-up OS called "Multics". Dude named ken thompson or dennis ritchie or something worked on it but was like "bro, so bloated". So dude writes a DISK BENCHMARKING system, single user, called it "Unix" as if to castrate multics. The original unix was disk benchmarking, barebones. So we know how that moved into multi-user source: kernighans readingbook, "unix a memoir" or something like that, great read
- kbolino 2y ago
  I'm not sure how much that really counts. According to [1], the time that Unix spent as a single-user operating system was intentionally very short-lived. Even the earliest version of the operating system that can be reconstructed today had multiple logins and processes, though only one could be active at a time. It seems that, by the time Unix was written in C, ported to multiple architectures, and spreading outside of Bell Labs, it was already multi-user. [1] https://retrocomputing.stackexchange.com/a/10908 https://retrocomputing.stackexchange.com/a/10908

hypercube33 2y ago

NT is closer to a mainframe OS than 9x and it came out in the win3 era

kbolino 2y ago
Yeah, I actually used NT 3.51 for some time. However it was the NT line that replaced the 9x line, at least from the consumer perspective.

nullindividual 2y ago

NT had no predecessor (at least from Microsoft; architecturally it's predecessor would be VMS). It was ground-up multi-user. Mac OS [Classic] was not OS X's predecessor, either -- it was NeXTStep.

kbolino 2y ago
You are right on the technical lineage, but I was referring to how these products were (ultimately) presented commercially. The facts that they are both older than one might think and they were developed with specific goals from the start I think more clearly illustrate that you can't just "bolt on" such fundamental differences.

fasa99 2y ago

yea, a big one. Once there was an intentionally multi-user-from-ground-up OS called "Multics". Dude named ken thompson or dennis ritchie or something worked on it but was like "bro, so bloated". So dude writes a DISK BENCHMARKING system, single user, called it "Unix" as if to castrate multics. The original unix was disk benchmarking, barebones. So we know how that moved into multi-user source: kernighans readingbook, "unix a memoir" or something like that, great read

kbolino 2y ago
I'm not sure how much that really counts. According to [1], the time that Unix spent as a single-user operating system was intentionally very short-lived. Even the earliest version of the operating system that can be reconstructed today had multiple logins and processes, though only one could be active at a time. It seems that, by the time Unix was written in C, ported to multiple architectures, and spreading outside of Bell Labs, it was already multi-user. [1] https://retrocomputing.stackexchange.com/a/10908 https://retrocomputing.stackexchange.com/a/10908