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The things like the TYPE command, the DEL command, the 8.3 case insensitive filenames (6.3 for RT-11), the / for switches, the drive:, CRLF, etc. Anyone using R

The things like the TYPE command, the DEL command, the 8.3 case insensitive filenames (6.3 for RT-11), the / for switches, the drive:, CRLF, etc. Anyone using RT-11 could pick up MSDOS in about 5 minutes. I know I did (I had an H-11, and bought an IBM PC). I bought a hard disk drive for my H-11, wire-wrapped an interface board for it, and wrote the device driver for it. It was a fun project, and didn't take much time. It was straightforward. I even got RT-11 to bootstrap off of it. Sorry, I don't think any of that stuff is a work of genius. My profile pic on twitter is of the machine: https://x.com/WalterBright https://x.com/WalterBright from before I added the HDD. It's also been 40 some years since I touched an 11, so my memory of the details needs a refresh :-/

kragen 2y ago
Some of the things you're talking about are features MS-DOS had in common with RT-11 but where CP/M was totally different; specifically, DEL was called ERA on CP/M, and CP/M didn't have switches. (Except PIP, which, bizarrely, wrapped its switches in square brackets: PIP A:=B:*.COM[W]. See https://ia902808.us.archive.org/23/items/osborne-cpm-users-guide_2nd-ed/OsborneCpmUsersGuideSecondEdition.pdf#page=80 https://ia902808.us.archive.org/23/items/osborne-cpm-users-g...) MS-DOS got drive letters from CP/M; on RT-11, as you might remember, instead of A:, B:, C:, etc., you had SY0:, SY1:, and DK:. (HDOS copied that, as well as /switches.) I'm not sure where the 8.3 filenames are from, but CP/M and MS-DOS had them, and, as you say, RT-11 didn't, using 6.3 instead. So, of the six similarities you listed between CP/M and RT-11, four were actually differences; only two were actually similarities (the TYPE command and the use of CRLF), with a third debatable one (8.3 is like 6.3 in that a three-character file type code forms part of the filename in some contexts). If CP/M had used RADIX-50 like RT-11 did, it could have had case-insensitive 9.3 filenames in 8 bytes instead of 8.3 filenames in 11 bytes. I think that would have been a big improvement. So, I don't think any of CP/M's deviations from RT-11 are a "work of genius", but it wasn't just a copy of RT-11, "little different", as you say. It clearly deviated from RT-11 in a lot of ways, to an extent that suggests drawing from some other source. Maybe RSX-11, dunno. The page you link to just says "Sign in to Twitter". For the sake of courtesy, I'd rather not go into how I feel about that invitation.
- WalterBright 2y ago
  The differences such as A: vs SY0:, are differences only in detail. The unix command line is fundamentally different, not just different in detail. BTW, RT-11 used PIP. > The page you link to just says "Sign in to Twitter". For the sake of courtesy, I'd rather not go into how I feel about that invitation. It goes to my profile page. Of course, I am logged in to twitter. I had no idea that it was necessary to sign in to twitter to see my profile page. There was no nefarious intent. I am not aware of any benefit that may accrue to me from you signing up for a twitter account.
  - kragen 2y ago
    I agree that Unix was fundamentally different in many ways, but CP/M wasn't a copy of Unix either; if anything, RT-11 was slightly more Unix-like than CP/M was. Because CP/M was evidently worse than RT-11 in many apparently unnecessary ways, I suspect that it was drawing from some other source. I didn't suspect any nefarious intent, but if I didn't tell you it had happened, you would never have known. My apologies if it sounded like I was blaming you for it.
    - WalterBright 2y ago
      I don't see any heritage of unix in CP/M, but I do see a heritage from DEC. Not an exact copy, of course. > if I didn't tell you it had happened, you would never have known That's right, and now I know. Thanks! > My apologies if it sounded like I was blaming you for it. Thank you. Apology accepted!
      - kragen 2y ago
        Do you have any clues about which DEC system it might be drawing these other elements from? I mean specifically: - FCBs. - A command interpreter prompt ending in ">" rather than "*" or ".". - 8-character filenames (rather than 6). - ASCII filenames (rather than RADIX-50). - Drive letters. - PIP switches in square brackets rather than introduced by slashes. (Some TENEX programs evidently enclosed their switches in parentheses, but the ones I've seen so far don't use square brackets.) - Launching programs from the command interpreter with command-line arguments, like Unix. Maybe Kildall thought all these things up himself, but I suspect some previous DEC OS was their origin. But it isn't RT-11, TENEX, the DEC 10/50 monitor, TOPS-20, or VMS. I want to emphasize I'm not claiming that these are advances or innovations. I'm just saying that they suggest some other influence.

kragen 2y ago

Some of the things you're talking about are features MS-DOS had in common with RT-11 but where CP/M was totally different; specifically, DEL was called ERA on CP/M, and CP/M didn't have switches. (Except PIP, which, bizarrely, wrapped its switches in square brackets: PIP A:=B:*.COM[W]. See https://ia902808.us.archive.org/23/items/osborne-cpm-users-guide_2nd-ed/OsborneCpmUsersGuideSecondEdition.pdf#page=80 https://ia902808.us.archive.org/23/items/osborne-cpm-users-g...) MS-DOS got drive letters from CP/M; on RT-11, as you might remember, instead of A:, B:, C:, etc., you had SY0:, SY1:, and DK:. (HDOS copied that, as well as /switches.) I'm not sure where the 8.3 filenames are from, but CP/M and MS-DOS had them, and, as you say, RT-11 didn't, using 6.3 instead. So, of the six similarities you listed between CP/M and RT-11, four were actually differences; only two were actually similarities (the TYPE command and the use of CRLF), with a third debatable one (8.3 is like 6.3 in that a three-character file type code forms part of the filename in some contexts). If CP/M had used RADIX-50 like RT-11 did, it could have had case-insensitive 9.3 filenames in 8 bytes instead of 8.3 filenames in 11 bytes. I think that would have been a big improvement. So, I don't think any of CP/M's deviations from RT-11 are a "work of genius", but it wasn't just a copy of RT-11, "little different", as you say. It clearly deviated from RT-11 in a lot of ways, to an extent that suggests drawing from some other source. Maybe RSX-11, dunno. The page you link to just says "Sign in to Twitter". For the sake of courtesy, I'd rather not go into how I feel about that invitation.

WalterBright 2y ago
The differences such as A: vs SY0:, are differences only in detail. The unix command line is fundamentally different, not just different in detail. BTW, RT-11 used PIP. > The page you link to just says "Sign in to Twitter". For the sake of courtesy, I'd rather not go into how I feel about that invitation. It goes to my profile page. Of course, I am logged in to twitter. I had no idea that it was necessary to sign in to twitter to see my profile page. There was no nefarious intent. I am not aware of any benefit that may accrue to me from you signing up for a twitter account.
- kragen 2y ago
  I agree that Unix was fundamentally different in many ways, but CP/M wasn't a copy of Unix either; if anything, RT-11 was slightly more Unix-like than CP/M was. Because CP/M was evidently worse than RT-11 in many apparently unnecessary ways, I suspect that it was drawing from some other source. I didn't suspect any nefarious intent, but if I didn't tell you it had happened, you would never have known. My apologies if it sounded like I was blaming you for it.
  - WalterBright 2y ago
    I don't see any heritage of unix in CP/M, but I do see a heritage from DEC. Not an exact copy, of course. > if I didn't tell you it had happened, you would never have known That's right, and now I know. Thanks! > My apologies if it sounded like I was blaming you for it. Thank you. Apology accepted!
    - kragen 2y ago
      Do you have any clues about which DEC system it might be drawing these other elements from? I mean specifically: - FCBs. - A command interpreter prompt ending in ">" rather than "*" or ".". - 8-character filenames (rather than 6). - ASCII filenames (rather than RADIX-50). - Drive letters. - PIP switches in square brackets rather than introduced by slashes. (Some TENEX programs evidently enclosed their switches in parentheses, but the ones I've seen so far don't use square brackets.) - Launching programs from the command interpreter with command-line arguments, like Unix. Maybe Kildall thought all these things up himself, but I suspect some previous DEC OS was their origin. But it isn't RT-11, TENEX, the DEC 10/50 monitor, TOPS-20, or VMS. I want to emphasize I'm not claiming that these are advances or innovations. I'm just saying that they suggest some other influence.