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MS-DOS (and PC-DOS) also didn’t have subdirectories until version 2.0. These were floppy disk oriented operating systems, and at 360 kB per floppy, directories

by pavlov 2y ago

MS-DOS (and PC-DOS) also didn’t have subdirectories until version 2.0. These were floppy disk oriented operating systems, and at 360 kB per floppy, directories were not really that useful. Hard disk support made it more urgent to offer Unix-style directories. Since the forward slash was already used for CLI parameters in the CP/M style, it couldn’t be used as the path separator. So Microsoft chose the backslash instead, and it persists in Windows today.

ghaff 2y ago
And arguably more file loaders than operating systems as such. I long thought it a sort of interesting question how things could have turned out differently if one of the many 16-bit operating systems (or Unix of course) kicking around in the minicomputer world had been more widely used on early PCs.
- dfawcus 2y ago
  Some of the products mention on that piece were true operating systems. MP/M and its derivatives (MP/M-86, CCPM, CDOS) were all multitasking, multi-threading, multi-user, multi-terminal/console real time preemptive OSs. The bank switching versions also had a form of memory protection. CDOS-68k, CDOS-286 and the subsequent renamed to FlexOS products also had those capabilities, but with inherent memory protection. So it is only really the basic CP/M-86 product (lacking the MP/M bits) which was the simple program loader. In many ways the FlexOS product are sort of inspired from the DEC minicomputer RSX-11m OS; and the MP/M derivatives look like they were inspired by DEC RSX-11d (and hence RSX-15).
  - ghaff 2y ago
    Fair enough. I suppose that hardware resource constraints were sufficiently tight at the time that the "mass market" wouldn't have thanked you for something that might have cost twice as much (at a time when micros were already quite expensive relative to today).
  - nickdothutton 2y ago
    I was an MP/M 2 user (Altos) for a while. It was a great system for a small workgroup, supporting a handful of (Volker Craig) Terminals. VT-52 clones IIRC.
- rbanffy 2y ago
  > And arguably more file loaders than operating systems as such That's a bit unfair. They also provided file operations and hardware abstraction. That way, it didn't matter how your disk IO was implemented (CP/M on Apple II's used the 6502 for that) and your code could be exactly the same.
gattilorenz 2y ago
> Since the forward slash was already used for CLI parameters in the CP/M style, it couldn’t be used as the path separator. So Microsoft chose the backslash instead, and it persists in Windows today. It's a bit more nuanced than that: https://www.os2museum.com/wp/why-does-windows-really-use-backslash-as-path-separator/ https://www.os2museum.com/wp/why-does-windows-really-use-bac... And see also https://learn.microsoft.com/it-it/archive/blogs/larryosterman/why-is-the-dos-path-character https://learn.microsoft.com/it-it/archive/blogs/larryosterma... for the SWITCHAR option, which would configure DOS 2.0 to use "-" as a parameter and "/" as a path separator.

by pavlov 2y ago

ghaff 2y ago

And arguably more file loaders than operating systems as such. I long thought it a sort of interesting question how things could have turned out differently if one of the many 16-bit operating systems (or Unix of course) kicking around in the minicomputer world had been more widely used on early PCs.

dfawcus 2y ago
Some of the products mention on that piece were true operating systems. MP/M and its derivatives (MP/M-86, CCPM, CDOS) were all multitasking, multi-threading, multi-user, multi-terminal/console real time preemptive OSs. The bank switching versions also had a form of memory protection. CDOS-68k, CDOS-286 and the subsequent renamed to FlexOS products also had those capabilities, but with inherent memory protection. So it is only really the basic CP/M-86 product (lacking the MP/M bits) which was the simple program loader. In many ways the FlexOS product are sort of inspired from the DEC minicomputer RSX-11m OS; and the MP/M derivatives look like they were inspired by DEC RSX-11d (and hence RSX-15).
- ghaff 2y ago
  Fair enough. I suppose that hardware resource constraints were sufficiently tight at the time that the "mass market" wouldn't have thanked you for something that might have cost twice as much (at a time when micros were already quite expensive relative to today).
- nickdothutton 2y ago
  I was an MP/M 2 user (Altos) for a while. It was a great system for a small workgroup, supporting a handful of (Volker Craig) Terminals. VT-52 clones IIRC.
rbanffy 2y ago
> And arguably more file loaders than operating systems as such That's a bit unfair. They also provided file operations and hardware abstraction. That way, it didn't matter how your disk IO was implemented (CP/M on Apple II's used the 6502 for that) and your code could be exactly the same.

gattilorenz 2y ago

> Since the forward slash was already used for CLI parameters in the CP/M style, it couldn’t be used as the path separator. So Microsoft chose the backslash instead, and it persists in Windows today. It's a bit more nuanced than that: https://www.os2museum.com/wp/why-does-windows-really-use-backslash-as-path-separator/ https://www.os2museum.com/wp/why-does-windows-really-use-bac... And see also https://learn.microsoft.com/it-it/archive/blogs/larryosterman/why-is-the-dos-path-character https://learn.microsoft.com/it-it/archive/blogs/larryosterma... for the SWITCHAR option, which would configure DOS 2.0 to use "-" as a parameter and "/" as a path separator.