9. Multics was developed in PL/I which the designers described as "maintainable". Since then we’ve seen the rise of C and C++ for low-level operating system development. What is your assessment of modern software development in C/C++ compared to the Multics and mainframe-era tools?
When we started Multics, machine language programming was the norm for building systems. Our choice of PL/I was probably too ambitious, but we did manage to make it work out.
We of course could not have used C because Ken Thompson had not yet invented it! In fact, Ken who had learned about the language BCPL (installed on CTSS by its inventor, Martin Richards) while working on Multics, was influenced to develop the language B for his own use.
When Bell Labs had to withdraw from the Multics project, Ken began to use B to develop Unix and soon the language evolved to what we now know as C.
But coming back to your question, today's programming environment is often one of modular composition which is one reason that systems, such as Windows, have become incredibly huge. So I do not think the choice of programming language is the only issue.
10. Another thing Multics pioneered was the concept of software being “open” and not tied to any one particular hardware platform. At the time did you envisage the operating system and application software market would blossom the way it did?
In those days, and still today, each system is "glued" to its own hardware architecture. In particular, the requirements for segmentation, paging and memory protection were not available in other hardware platforms. In any case, we viewed the Multics system as an example, not as the system for all time.
11. According to MIT, its last Multics service was shutdown in 1988 -- what was it like seeing it turned off? What was it doing and what was it replaced with?
Of course it was sad seeing Multics turned off at MIT, but the economics of distributed computing had changed. In particular the hardware base was not being modernized. At MIT Multics was used as a general-purpose computer by a wide variety of researchers.
By 1988, the Internet and local area networks were in full flower, so that many locally managed machines were already in place and widely used.
12. The last Multics system ever was shut down in 2000, which meant it lasted through 35 years of practical service. What’s your assessment of the longevity of Multics and do you think modern operating systems can last so long?
The real legacy of Multics was the education and inculcation of system engineering principles in over 1400 people directly associated with operating, maintaining, extending and managing the system during its lifetime. Because we made documentation and publications a mainstay of the project, countless others have also been influenced.
13. Could Multics have been “modernized” to keep it going even longer the same way modern operating systems are continuously ported to new architectures and adding new features?
Given a continual stream of new hardware, I believe Multics could have been migrated. But you are asking an economic question. Without a large user base and a promising business plan, it is unlikely that any company would make such an investment in today's competitive world.
In any case, today most modern hardware changes are just "tweaks" of the previous design, so that moving the operating system is much simpler.
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