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Speaking of PL/I, Intel made a few operating systems in the late 70s / early 80s written in their dialect of PL/I called PL/M. There was ISIS, which ran on the

Speaking of PL/I, Intel made a few operating systems in the late 70s / early 80s written in their dialect of PL/I called PL/M. There was ISIS, which ran on their microprocessor development stations, and iRMX, the real time O/S running on the target microprocessors. Having used both, ISIS was quite a bit more advanced than 'competitors' like DOS and CP/M at the time.

skissane 5y ago
> Speaking of PL/I, Intel made a few operating systems in the late 70s / early 80s written in their dialect of PL/I called PL/M PL/M was created by Gary Kildall, creator of CP/M, and CP/M 1.x was written in PL/M. In CP/M-80 2.x, they rewrote the kernel (BDOS) and command processor (CCP) in 8080 assembly to improve performance, but utility programs were still written in PL/M. Some later CP/M ports, such as CP/M-68K and CP/M-8000, were written in C instead. Wikipedia says that IBM used PL/M too – to write some of the firmware for the CISC AS/400s (the Service Processor).
- kragen 5y ago
  I think those might be two different PL/Ms that were both born in the 01970s.
  - skissane 5y ago
    They are the same PL/M. Gary Kildall was working at Intel as a contractor when he invented the first version of PL/M. Intel adopted it for their own internal software development (ISIS, RMX, etc), Kildall used it for writing CP/M and other Digital Research products. The compiler was forked into two versions – an Intel version and a Digital Research version – and they were mostly compatible, but each had some extensions the other lacked. As a result, code written for one couldn't always be compiled by the other.
    - kragen 5y ago
      Sorry, I was thinking of IBM's PL/M, which clearly wasn't the one Intel was using. Thanks for the correction.
      - skissane 5y ago
        Did IBM have a "PL/M"? IBM has had PL/MP and PL/MI but not (to my knowledge) a PL/M. Wikipedia claims (without a source) that the CISC AS/400 Service Processor firmware was written in Gary Kildall's PL/M. The claim seems very plausible – the Service Processor is not the main CPU, it is a microprocessor used to control system startup/etc. I'm not sure what microprocessor was used in the CISC AS/400's Service Processor, but IBM could well have chosen an Intel CPU (such as 80x86) for it; and if they did, Intel's PL/M compiler would have had a logical attraction – at the time (the AS/400 came out in 1988 so this would have been some time in the 1980s) Intel was still actively supporting it as an embedded systems development language; it had similar syntax to the systems programming PL/I dialects which IBM's developers were using for other parts of the AS/400 (PL/MI and PL/MP); using Intel's PL/M compiler would have avoided the need for IBM to implement an 80x86 backend for their PL/whatever compilers.
        kragen 5y ago
        I might be misremembering! My source is a friend of mine whose day job was maintaining DB2; about 15 years ago, she told me — if I'm not misremembering! — that DB2 was written in "PL/M", which was a variant of PL/I. But it wouldn't be terribly surprising if it was actually PL/MI or PL/MP or (as you suggest in https://news.ycombinator.com/item?id=30877856 https://news.ycombinator.com/item?id=30877856) PL/X and I just misheard. Or misremembered. She was also born around the time DB2 was first released, but she did work for IBM.

skissane 5y ago

> Speaking of PL/I, Intel made a few operating systems in the late 70s / early 80s written in their dialect of PL/I called PL/M PL/M was created by Gary Kildall, creator of CP/M, and CP/M 1.x was written in PL/M. In CP/M-80 2.x, they rewrote the kernel (BDOS) and command processor (CCP) in 8080 assembly to improve performance, but utility programs were still written in PL/M. Some later CP/M ports, such as CP/M-68K and CP/M-8000, were written in C instead. Wikipedia says that IBM used PL/M too – to write some of the firmware for the CISC AS/400s (the Service Processor).

kragen 5y ago
I think those might be two different PL/Ms that were both born in the 01970s.
- skissane 5y ago
  They are the same PL/M. Gary Kildall was working at Intel as a contractor when he invented the first version of PL/M. Intel adopted it for their own internal software development (ISIS, RMX, etc), Kildall used it for writing CP/M and other Digital Research products. The compiler was forked into two versions – an Intel version and a Digital Research version – and they were mostly compatible, but each had some extensions the other lacked. As a result, code written for one couldn't always be compiled by the other.
  - kragen 5y ago
    Sorry, I was thinking of IBM's PL/M, which clearly wasn't the one Intel was using. Thanks for the correction.
    - skissane 5y ago
      Did IBM have a "PL/M"? IBM has had PL/MP and PL/MI but not (to my knowledge) a PL/M. Wikipedia claims (without a source) that the CISC AS/400 Service Processor firmware was written in Gary Kildall's PL/M. The claim seems very plausible – the Service Processor is not the main CPU, it is a microprocessor used to control system startup/etc. I'm not sure what microprocessor was used in the CISC AS/400's Service Processor, but IBM could well have chosen an Intel CPU (such as 80x86) for it; and if they did, Intel's PL/M compiler would have had a logical attraction – at the time (the AS/400 came out in 1988 so this would have been some time in the 1980s) Intel was still actively supporting it as an embedded systems development language; it had similar syntax to the systems programming PL/I dialects which IBM's developers were using for other parts of the AS/400 (PL/MI and PL/MP); using Intel's PL/M compiler would have avoided the need for IBM to implement an 80x86 backend for their PL/whatever compilers.
      - kragen 5y ago
        I might be misremembering! My source is a friend of mine whose day job was maintaining DB2; about 15 years ago, she told me — if I'm not misremembering! — that DB2 was written in "PL/M", which was a variant of PL/I. But it wouldn't be terribly surprising if it was actually PL/MI or PL/MP or (as you suggest in https://news.ycombinator.com/item?id=30877856 https://news.ycombinator.com/item?id=30877856) PL/X and I just misheard. Or misremembered. She was also born around the time DB2 was first released, but she did work for IBM.