4 ms·

Multics

132 points by unleaded 1y ago

dmitrygr 1y ago
The “ Recent Changes” part of the site is depressing Recent Changes 08/03 Multicians: Jim Bush died in July 2025. 07/14 Multicians: Norm Barnecut died Dec 09, 2023. 05/24 Multicians: Nate Adleman died Sept 19, 2022. 05/15 Simulator: Release 3.1.0 of the DPS8M simulator was released. 05/12 Multicians: Richard Gardner died in 2025. 05/05 Multicians: Art Bushkin died in Feb 2024.
- mysh 1y ago
  You can see exactly how many people have died on their log page: https://www.multicians.org/changes-old.html https://www.multicians.org/changes-old.html At this moment in time, 125.
  - BXLE_1-1-BitIs1 1y ago
    20- & 30- somethings in the 80s are now mostly past retirement age. Actuarial attrition is a fact.
- freetime2 1y ago
  I went and looked up my former CS professor who I knew had worked on Multics. And unfortunately learned that he had passed away a few years ago.
CSP_Jobs 1y ago
Always fun to see Multics pop up; the influence it had on computing is pretty impressive and its influence lives on in many projects. As just one personally relevant example, the SCOMP mentioned in the glossary [0] and described in more detail on the history page under 5.4.1 [1] became the STOP operating system which is still in active development and is what I still work on today. (Technically, the SCOMP was the whole machine, and STOP "SCOMP Trusted Operating Program" was its operating system). Up until pretty recently, we still had a Multician working on STOP, and have a guy from the Honewell days still plugging away on it. [0]https://www.multicians.org/mgs.html#SCOMP https://www.multicians.org/mgs.html#SCOMP [1]https://www.multicians.org/history.html https://www.multicians.org/history.html
- dillona 1y ago
  This operating system sounds very interesting! How active is the development? I would imagine it's the type of thing that eventually gets "complete"
  - CSP_Jobs 1y ago
    I've been gainfully employed for well over a decade working on it and it's been around in one form or another for over 40 years. We're constantly improving performance and capabilities, adding support for more hardware, supporting the specific needs of our customers etc... Just like any modern operating system, it's never really "complete". STOP is a "security from the ground up" OS, where security isn't just a first-order priority, it's the entire point, typically used in/as multilevel security solutions.
    - rbanffy 1y ago
      Are there any documents we can use to learn more about it? What does it look like to the user? Is it intended to be embedded?
      - CSP_Jobs 1y ago
        There's a link in my profile to the company products page for my group, which includes a link to the STOP OS page. There used to be additional documents you could download from those pages, but it looks like they're not working any more. The short version is that it implements three different MAC (mandatory access control) policies (RBAC, Bell-LaPadula, Biba) and the standard *nix DAC policies. It's designed for safely handling/moving data on/between multiple classification levels. (See the SCOMP section in [0] for history). From a user perspective, it's very similar to Linux, with a largely Linux-like ABI and similar user interfaces, including a full X/xfce GUI environment if you want, though most actual deployments tend to run headless with only required software loaded. It runs on both small embedded boards and large enterprise servers and a bunch in between. [0] https://multicians.org/b2.html https://multicians.org/b2.html
GlenTheMachine 1y ago
My Operating Systems class as an undergrad used a book written by the Multics guys. I hated it. It would present a bunch of apparently incompatible techniques for e.g. job scheduling, and then say that Multics implemented all of them. I immediately understood why UNIX came about: the Multics designers appeared incapable of having opinions, which led to an OS that was bloated and hard to understand. That class was a long time ago, and I was a young, arrogant, and uninformed programmer, and maybe that take was wrong. But it left a strong impression at the time, and it was one of the few books from my undergrad days that I sold back instead of keeping.
tovej 1y ago
Thanks! This is a really useful source for computer science history, I was just thinking to myself that I keep reading UNIX history, but that I know very little about Multics. Looks like I can keep my evening busy for quite some time with this one.
- pjmlp 1y ago
  For a little while at the university I became what happens to many software engineering students, a UNIX zealot that used to write email signatures with the usual M$ joke back then. Then the university library opened my eyes to the world of Xerox PARC, and the computing decades that predated UNIX, and my point of view changed forever, that cloning UNIX all the time couldn't be the epitome of OS design. At least I agree with Rob Pike in something, "Using Unix is the computing equivalent of listening only to music by David Cassidy" From https://interviews.slashdot.org/story/04/10/18/1153211/rob-pike-responds https://interviews.slashdot.org/story/04/10/18/1153211/rob-p...
  - musicale 1y ago
    I wonder who the appropriate musician is for Windows? (Note Windows also has a Posix compatibility layer - WSL1; WSL2 probably qualifies as using Linux, albeit wrapped in a VM.)
pjmlp 1y ago
Quite interesting are the collection of myths, https://www.multicians.org/myths.html https://www.multicians.org/myths.html And naturally, B2 Security Evaluation, https://multicians.org/b2.html https://multicians.org/b2.html
- leoc 1y ago
  It's also the home of the Three Questions (about each bug you find): https://www.multicians.org/thvv/threeq.html https://www.multicians.org/thvv/threeq.html
- dismas 1y ago
  The Data Security page is very interesting as well: https://multicians.org/multics-data-security.html https://multicians.org/multics-data-security.html AIM and MAC seem like a very interesting system for enforcing security guarantees, and they partially solved the malicious dependencies problem as well.
unleaded 1y ago
my personal favourite page: https://www.multicians.org/memorabilia.html https://www.multicians.org/memorabilia.html
dang 1y ago
Related: Unix and Multics (2019) - https://news.ycombinator.com/item?id=40315724 https://news.ycombinator.com/item?id=40315724 - May 2024 (76 comments) Unix and Multics History - https://news.ycombinator.com/item?id=40065928 https://news.ycombinator.com/item?id=40065928 - April 2024 (3 comments) Multics and AS400：DPS8M on IBM PASE for I (OS/400) - https://news.ycombinator.com/item?id=39308420 https://news.ycombinator.com/item?id=39308420 - Feb 2024 (4 comments) Multics Simulator - https://news.ycombinator.com/item?id=37304367 https://news.ycombinator.com/item?id=37304367 - Aug 2023 (15 comments) So! You want to use Multics? (1979) [pdf] - https://news.ycombinator.com/item?id=33366716 https://news.ycombinator.com/item?id=33366716 - Oct 2022 (5 comments) Wordmul: Wordle for Multics - https://news.ycombinator.com/item?id=31636949 https://news.ycombinator.com/item?id=31636949 - June 2022 (3 comments) Nobody learned the most important lesson from Multics vs. Unix - https://news.ycombinator.com/item?id=29783423 https://news.ycombinator.com/item?id=29783423 - Jan 2022 (1 comment) Multics MR12.7 released - https://news.ycombinator.com/item?id=28006036 https://news.ycombinator.com/item?id=28006036 - July 2021 (25 comments) Multics Public Access - https://news.ycombinator.com/item?id=27128765 https://news.ycombinator.com/item?id=27128765 - May 2021 (33 comments) Ban.ai Public Access Multics - https://news.ycombinator.com/item?id=25611468 https://news.ycombinator.com/item?id=25611468 - Jan 2021 (6 comments) Multics Simulator - https://news.ycombinator.com/item?id=22994027 https://news.ycombinator.com/item?id=22994027 - April 2020 (20 comments) Multics: An Ancestor of Unix - https://news.ycombinator.com/item?id=21892923 https://news.ycombinator.com/item?id=21892923 - Dec 2019 (33 comments) Multics Intro Course (1978) - https://news.ycombinator.com/item?id=18715014 https://news.ycombinator.com/item?id=18715014 - Dec 2018 (9 comments) Thirty Years Later: Lessons from the Multics Security Evaluation (2002) [pdf] - https://news.ycombinator.com/item?id=16956386 https://news.ycombinator.com/item?id=16956386 - April 2018 (3 comments) Public Access Multics - https://news.ycombinator.com/item?id=16875552 https://news.ycombinator.com/item?id=16875552 - April 2018 (3 comments) 48-Year-Old Multics operating system resurrected - https://news.ycombinator.com/item?id=14728441 https://news.ycombinator.com/item?id=14728441 - July 2017 (9 comments) Multics Execution Environment (2014) - https://news.ycombinator.com/item?id=10364234 https://news.ycombinator.com/item?id=10364234 - Oct 2015 (1 comment) Introduction to Multics - https://news.ycombinator.com/item?id=6985277 https://news.ycombinator.com/item?id=6985277 - Dec 2013 (1 comment)
HarHarVeryFunny 1y ago
We used Multics when I was at Bristol Uni in the UK c.1980. I can only remember two things about it: 1) The system was initially deemed slow, so they installed an extra 256 KB of RAM (for a system serving dozens/hundreds of students - Bristol was regional computing center), and that made a difference! This was a big deal - apparently quite expensive! 2) Notwithstanding 1), it was fast, and typical student FORTRAN assignments of a 100 or so lines of code would compile and link essentially instantly - hit enter and get prompt back. I wish compilers were this fast today on 2025's massively faster hardware!
- quatonion 1y ago
  Same where I went at Leeds Uni in the mid 80s. Ours was just for CS undergrads mostly when I was there, and wasn't too overloaded. I guess we had about fifty terminals maybe on campus at least. I remember we could dial it up from a couple of terminals in our Halls of Residence over JANET. You are right, I never found it that slow either - loved that machine and the terminal to terminal messaging was crazy fun.
aatd86 1y ago
One unix, two multics. /jk
- fuzztester 1y ago
  zero xenix :) cuz (almost) no one uses it any more. i did, a bit long ago.
rpiguy 1y ago
There was at least one Multics server with users at RPI when I graduated in 1999. I wonder how long it persisted.
- bilegeek 1y ago
  Can't find anything about RPI, but apparently the last known site was shut down in 2000: https://multicians.org/site-dndh.html https://multicians.org/site-dndh.html
musicale 1y ago
A few multics features that I wish unix/linux had: - ring based security (allows for multilevel containers at user level, among other things) - better permissions by default (mandatory access control, acls, etc.) - finer-grain memory permissions (segments vs. pages, etc.) - no buffer overflows (and minimal memory errors) - long command names in addition to short abbreviations (easy to implement in linux/unix, just missing) - multiple entry points for commands (currently faked with symlinks) - (related) being able to call into an executable like a library - unified storage model (can sort of be faked with mmap()) and some features I wish unix didn't have (and which multics didn't need): - dumping new kernel APIs into /proc Ironically linux is much larger than multics ever was, but much (most?) of it isn't basic kernel functionality but things like libraries, tons of drivers for everything imaginable, lots of network protocols, file systems, etc., and a bunch of kernel modules.
- fuzztester 1y ago
  >better permissions by default (mandatory access control, acls, etc.) i thought some unixen had acls? i remember reading some man pages about that, i think on an svr4 box, back in the day.
- msla 1y ago
  > tons of drivers for everything imaginable Better than going the Multics way, which was being theoretically portable but not actually capable of being ported off a very short list (two... a list of two) mainframe computers that implement an architecture with no future.
  - musicale 1y ago
    I certainly agree that drivers and portability are Linux's best features (NetBSD scores even better on portability and compatibility.) The point of the comparison was to say that the code and memory size cost of Multics (and its core functionality and abstractions) was considered prohibitive in 1969 when Unix was being created, but is basically in the noise for systems like Linux in 2025. Sadly segmentation fell out of vogue and was dropped from x86 because ... no OS ended up using it! (Though it was used in the 32-bit implementation of Google Native Client, a sandboxed environment for safely running x86 code.) But a Multics-informed design is not inherently unportable or antithetical to drivers. Ring-based security can allow for better isolation and easier driver development. Maybe even ingesting and reusing all of those linux drivers?
LAC-Tech 1y ago
This such a rabbit hole. I only really knew of multics as 'the thing before unix'. I had no idea it was interesting in its own right. I have to stop myself reading or I'll be downloading the papers (I love old comp sci papers)... From the front page: "preserve the technical ideas and advances of Multics so others don't need to reinvent them" Which ideas and advances from multics do we not do anymore?

132 points by unleaded 1y ago

The “ Recent Changes” part of the site is depressing Recent Changes 08/03 Multicians: Jim Bush died in July 2025. 07/14 Multicians: Norm Barnecut died Dec 09, 2023. 05/24 Multicians: Nate Adleman died Sept 19, 2022. 05/15 Simulator: Release 3.1.0 of the DPS8M simulator was released. 05/12 Multicians: Richard Gardner died in 2025. 05/05 Multicians: Art Bushkin died in Feb 2024.

mysh 1y ago
You can see exactly how many people have died on their log page: https://www.multicians.org/changes-old.html https://www.multicians.org/changes-old.html At this moment in time, 125.
- BXLE_1-1-BitIs1 1y ago
  20- & 30- somethings in the 80s are now mostly past retirement age. Actuarial attrition is a fact.
freetime2 1y ago
I went and looked up my former CS professor who I knew had worked on Multics. And unfortunately learned that he had passed away a few years ago.

CSP_Jobs 1y ago

Always fun to see Multics pop up; the influence it had on computing is pretty impressive and its influence lives on in many projects. As just one personally relevant example, the SCOMP mentioned in the glossary [0] and described in more detail on the history page under 5.4.1 [1] became the STOP operating system which is still in active development and is what I still work on today. (Technically, the SCOMP was the whole machine, and STOP "SCOMP Trusted Operating Program" was its operating system). Up until pretty recently, we still had a Multician working on STOP, and have a guy from the Honewell days still plugging away on it. [0]https://www.multicians.org/mgs.html#SCOMP https://www.multicians.org/mgs.html#SCOMP [1]https://www.multicians.org/history.html https://www.multicians.org/history.html

dillona 1y ago
This operating system sounds very interesting! How active is the development? I would imagine it's the type of thing that eventually gets "complete"
- CSP_Jobs 1y ago
  I've been gainfully employed for well over a decade working on it and it's been around in one form or another for over 40 years. We're constantly improving performance and capabilities, adding support for more hardware, supporting the specific needs of our customers etc... Just like any modern operating system, it's never really "complete". STOP is a "security from the ground up" OS, where security isn't just a first-order priority, it's the entire point, typically used in/as multilevel security solutions.
  - rbanffy 1y ago
    Are there any documents we can use to learn more about it? What does it look like to the user? Is it intended to be embedded?
    - CSP_Jobs 1y ago
      There's a link in my profile to the company products page for my group, which includes a link to the STOP OS page. There used to be additional documents you could download from those pages, but it looks like they're not working any more. The short version is that it implements three different MAC (mandatory access control) policies (RBAC, Bell-LaPadula, Biba) and the standard *nix DAC policies. It's designed for safely handling/moving data on/between multiple classification levels. (See the SCOMP section in [0] for history). From a user perspective, it's very similar to Linux, with a largely Linux-like ABI and similar user interfaces, including a full X/xfce GUI environment if you want, though most actual deployments tend to run headless with only required software loaded. It runs on both small embedded boards and large enterprise servers and a bunch in between. [0] https://multicians.org/b2.html https://multicians.org/b2.html

GlenTheMachine 1y ago

My Operating Systems class as an undergrad used a book written by the Multics guys. I hated it. It would present a bunch of apparently incompatible techniques for e.g. job scheduling, and then say that Multics implemented all of them. I immediately understood why UNIX came about: the Multics designers appeared incapable of having opinions, which led to an OS that was bloated and hard to understand. That class was a long time ago, and I was a young, arrogant, and uninformed programmer, and maybe that take was wrong. But it left a strong impression at the time, and it was one of the few books from my undergrad days that I sold back instead of keeping.

tovej 1y ago

Thanks! This is a really useful source for computer science history, I was just thinking to myself that I keep reading UNIX history, but that I know very little about Multics. Looks like I can keep my evening busy for quite some time with this one.

pjmlp 1y ago
For a little while at the university I became what happens to many software engineering students, a UNIX zealot that used to write email signatures with the usual M$ joke back then. Then the university library opened my eyes to the world of Xerox PARC, and the computing decades that predated UNIX, and my point of view changed forever, that cloning UNIX all the time couldn't be the epitome of OS design. At least I agree with Rob Pike in something, "Using Unix is the computing equivalent of listening only to music by David Cassidy" From https://interviews.slashdot.org/story/04/10/18/1153211/rob-pike-responds https://interviews.slashdot.org/story/04/10/18/1153211/rob-p...
- musicale 1y ago
  I wonder who the appropriate musician is for Windows? (Note Windows also has a Posix compatibility layer - WSL1; WSL2 probably qualifies as using Linux, albeit wrapped in a VM.)

pjmlp 1y ago

Quite interesting are the collection of myths, https://www.multicians.org/myths.html https://www.multicians.org/myths.html And naturally, B2 Security Evaluation, https://multicians.org/b2.html https://multicians.org/b2.html

leoc 1y ago
It's also the home of the Three Questions (about each bug you find): https://www.multicians.org/thvv/threeq.html https://www.multicians.org/thvv/threeq.html
dismas 1y ago
The Data Security page is very interesting as well: https://multicians.org/multics-data-security.html https://multicians.org/multics-data-security.html AIM and MAC seem like a very interesting system for enforcing security guarantees, and they partially solved the malicious dependencies problem as well.

unleaded 1y ago

my personal favourite page: https://www.multicians.org/memorabilia.html https://www.multicians.org/memorabilia.html

dang 1y ago

Related: Unix and Multics (2019) - https://news.ycombinator.com/item?id=40315724 https://news.ycombinator.com/item?id=40315724 - May 2024 (76 comments) Unix and Multics History - https://news.ycombinator.com/item?id=40065928 https://news.ycombinator.com/item?id=40065928 - April 2024 (3 comments) Multics and AS400：DPS8M on IBM PASE for I (OS/400) - https://news.ycombinator.com/item?id=39308420 https://news.ycombinator.com/item?id=39308420 - Feb 2024 (4 comments) Multics Simulator - https://news.ycombinator.com/item?id=37304367 https://news.ycombinator.com/item?id=37304367 - Aug 2023 (15 comments) So! You want to use Multics? (1979) [pdf] - https://news.ycombinator.com/item?id=33366716 https://news.ycombinator.com/item?id=33366716 - Oct 2022 (5 comments) Wordmul: Wordle for Multics - https://news.ycombinator.com/item?id=31636949 https://news.ycombinator.com/item?id=31636949 - June 2022 (3 comments) Nobody learned the most important lesson from Multics vs. Unix - https://news.ycombinator.com/item?id=29783423 https://news.ycombinator.com/item?id=29783423 - Jan 2022 (1 comment) Multics MR12.7 released - https://news.ycombinator.com/item?id=28006036 https://news.ycombinator.com/item?id=28006036 - July 2021 (25 comments) Multics Public Access - https://news.ycombinator.com/item?id=27128765 https://news.ycombinator.com/item?id=27128765 - May 2021 (33 comments) Ban.ai Public Access Multics - https://news.ycombinator.com/item?id=25611468 https://news.ycombinator.com/item?id=25611468 - Jan 2021 (6 comments) Multics Simulator - https://news.ycombinator.com/item?id=22994027 https://news.ycombinator.com/item?id=22994027 - April 2020 (20 comments) Multics: An Ancestor of Unix - https://news.ycombinator.com/item?id=21892923 https://news.ycombinator.com/item?id=21892923 - Dec 2019 (33 comments) Multics Intro Course (1978) - https://news.ycombinator.com/item?id=18715014 https://news.ycombinator.com/item?id=18715014 - Dec 2018 (9 comments) Thirty Years Later: Lessons from the Multics Security Evaluation (2002) [pdf] - https://news.ycombinator.com/item?id=16956386 https://news.ycombinator.com/item?id=16956386 - April 2018 (3 comments) Public Access Multics - https://news.ycombinator.com/item?id=16875552 https://news.ycombinator.com/item?id=16875552 - April 2018 (3 comments) 48-Year-Old Multics operating system resurrected - https://news.ycombinator.com/item?id=14728441 https://news.ycombinator.com/item?id=14728441 - July 2017 (9 comments) Multics Execution Environment (2014) - https://news.ycombinator.com/item?id=10364234 https://news.ycombinator.com/item?id=10364234 - Oct 2015 (1 comment) Introduction to Multics - https://news.ycombinator.com/item?id=6985277 https://news.ycombinator.com/item?id=6985277 - Dec 2013 (1 comment)

HarHarVeryFunny 1y ago

We used Multics when I was at Bristol Uni in the UK c.1980. I can only remember two things about it: 1) The system was initially deemed slow, so they installed an extra 256 KB of RAM (for a system serving dozens/hundreds of students - Bristol was regional computing center), and that made a difference! This was a big deal - apparently quite expensive! 2) Notwithstanding 1), it was fast, and typical student FORTRAN assignments of a 100 or so lines of code would compile and link essentially instantly - hit enter and get prompt back. I wish compilers were this fast today on 2025's massively faster hardware!

quatonion 1y ago
Same where I went at Leeds Uni in the mid 80s. Ours was just for CS undergrads mostly when I was there, and wasn't too overloaded. I guess we had about fifty terminals maybe on campus at least. I remember we could dial it up from a couple of terminals in our Halls of Residence over JANET. You are right, I never found it that slow either - loved that machine and the terminal to terminal messaging was crazy fun.

aatd86 1y ago

One unix, two multics. /jk

fuzztester 1y ago
zero xenix :) cuz (almost) no one uses it any more. i did, a bit long ago.

rpiguy 1y ago

There was at least one Multics server with users at RPI when I graduated in 1999. I wonder how long it persisted.

bilegeek 1y ago
Can't find anything about RPI, but apparently the last known site was shut down in 2000: https://multicians.org/site-dndh.html https://multicians.org/site-dndh.html

musicale 1y ago

A few multics features that I wish unix/linux had: - ring based security (allows for multilevel containers at user level, among other things) - better permissions by default (mandatory access control, acls, etc.) - finer-grain memory permissions (segments vs. pages, etc.) - no buffer overflows (and minimal memory errors) - long command names in addition to short abbreviations (easy to implement in linux/unix, just missing) - multiple entry points for commands (currently faked with symlinks) - (related) being able to call into an executable like a library - unified storage model (can sort of be faked with mmap()) and some features I wish unix didn't have (and which multics didn't need): - dumping new kernel APIs into /proc Ironically linux is much larger than multics ever was, but much (most?) of it isn't basic kernel functionality but things like libraries, tons of drivers for everything imaginable, lots of network protocols, file systems, etc., and a bunch of kernel modules.

fuzztester 1y ago
>better permissions by default (mandatory access control, acls, etc.) i thought some unixen had acls? i remember reading some man pages about that, i think on an svr4 box, back in the day.
msla 1y ago
> tons of drivers for everything imaginable Better than going the Multics way, which was being theoretically portable but not actually capable of being ported off a very short list (two... a list of two) mainframe computers that implement an architecture with no future.
- musicale 1y ago
  I certainly agree that drivers and portability are Linux's best features (NetBSD scores even better on portability and compatibility.) The point of the comparison was to say that the code and memory size cost of Multics (and its core functionality and abstractions) was considered prohibitive in 1969 when Unix was being created, but is basically in the noise for systems like Linux in 2025. Sadly segmentation fell out of vogue and was dropped from x86 because ... no OS ended up using it! (Though it was used in the 32-bit implementation of Google Native Client, a sandboxed environment for safely running x86 code.) But a Multics-informed design is not inherently unportable or antithetical to drivers. Ring-based security can allow for better isolation and easier driver development. Maybe even ingesting and reusing all of those linux drivers?

LAC-Tech 1y ago

This such a rabbit hole. I only really knew of multics as 'the thing before unix'. I had no idea it was interesting in its own right. I have to stop myself reading or I'll be downloading the papers (I love old comp sci papers)... From the front page: "preserve the technical ideas and advances of Multics so others don't need to reinvent them" Which ideas and advances from multics do we not do anymore?