CIO Blast from the Past: 40 years of Multics, 1969-2009

Multics pioneered hierarchical file systems, file access controls, and dynamic linking on demand

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Multics lead developer and Turing Award winner, MIT's Professor Fernando J. Corbato [photo by Jason Dorfman, Creative Commons Attribution and ShareAlike licence]

4. What are some of the features we enjoy in modern computing that were first developed (or conceived) with Multics? Many people know about things like multi-tasking, virtual memory, and component redundancy, but maybe there are some others that you could tell us about?

I would mention hierarchical file systems, file access controls and dynamic linking on demand.

5. More specifically, what in your view was the most profound way Multics influenced the development of Unix? Unix itself went on to influence modern operating systems like Linux and Mac OS X. Was Unix an improvement over Multics in terms of hardware utilization?

Multics was built top-down, that is, we had to lay out the full vision of the system before we started on the software. Unix had the chance to take a new run at the problem and build the system up from the bottom "brick by brick".

Ken Thompson was extremely shrewd in keeping the system lean but not rejecting ideas from Multics just to be different. Both Multics and Unix made effective use of their hardware and were useful.

6. There’s and old saying “those who do not understand Unix are condemned to reinvent it, poorly”. Does that sum up the excellence of the Unix design or the lack of operating system innovation since Unix?

I think the remark is a testimonial to the overall coherence of the Unix design and reflects that Unix was built by a small group.

7. If computing were to “move beyond” Unix-like (and Windows) operating systems where do you think it would go?

Efficiently harnessing parallelism is still a challenging problem that is not well addressed in contemporary systems. A radically different hardware architecture, such as Dataflow as advocated by Jack Dennis or the Monsoon machine of Arvind, certainly changes the landscape of operating systems.

Other issues are the indefinite archiving and retrieving of information, which are still very challenging problems. Also there are vexing matters of trust in the "Wild West" that is the Internet.

8. According to Wikipedia, the U in Unix (originally Unics as a play on Multics) is rumored to stand for uniplexed as opposed to the multiplexed of Multics, underscoring the designers' rejection of Multics' complexity in favor of a more straightforward and workable approach for smaller computers. Is this true? Are there any stories you have relating to the choice of the names Multics and Unix?

Multics was meant to be a serious name that suggested the intent of the system.

We specifically avoided any name that could be viewed as "cute" or be associated with any of the participants: MIT, Bell Labs or GE. Of course systems developed by small groups often had names tweaking older systems.

Our own CTSS (The Compatible Time-Sharing System) was joshed by the developers of ITS (The Incompatible Time-Sharing System) created in the AI Lab of Project Mac on a DEC PDP-6 (and later on a PDP-10). But basically Wikipedia has it right. Unix was a friendly pun on Multics.