Chapter 2. UNIX

In spring 1969, AT&T decided to terminate its involvement in a project called Multics -- Multiplexed Information and Computing Service -- which had been started in 1964 by MIT, GE and Bell Labs. This left those at AT&T Bell Labs who had been working on the project -- notably Doug McIlroy, Dennis Ritchie and Ken Thompson -- at loose ends. Doug immediately got involved with other things in Murray Hill, NJ, but Dennis and Ken had been interested in the project per se and wanted to explore several of its ideas.

Ken has said:

Dennis and [Rudd] Canaday and I were discussing these ideas of the general nature of keeping the files out of each other's hair and the nitty-gritty of expanding, of the real implementation where you put block addresses... We did it in Canaday's office, and, at the end of the discussion, Canaday picked up the phone; there was a new service at Bell Laboratories that took dictation. You call up essentially a tape recorder and you give notes, and then the next morning the notes are typed and sent to you. The next day these notes came back, and all the acronyms were butchered, like 'inode' was 'eyen...'. So we got back these descriptions and they were copied, and we each had copies of them and they became the working document for the file system -- which was just built in a day or two on the PDP-7.
At first ... we used it for other things, you know, the famous Space Travel game, and it was the natural candidate as the place to put the file system. When we hacked out this design, this rough design of the file system on the dictation [machine] that day in Canaday's office, I went off and implemented it on the PDP-7.

I won't go into full detail on the evolution of that file system on the PDP-7 to Unics [Uniplexed Information and Computing Service, a pun on cut-down (emasculated) Multics devised by Peter Neumann, an inveterate punster. 1 Several people told me that Brian Kernighan had changed the spelling to UNIX, but Brian told me that he had not, and that no one recalled who had done it.] For now, it is important to realize that it was the cooperative product of several brilliant minds: Ritchie, Thompson and Canaday, of whom Robert Morris (who joined Bell Labs in 1960 and is now Chief Scientist at the National Computer Security Center in Maryland) said he was the "most underrated" of the original participants. 2

In August 1969. Ken Thompson's wife Bonnie took their year-old son on a trip to California to show off to their families. As a temporary bachelor, Ken had time to work.

I allocated a week each to the operating system, the shell, the editor and the assembler [he told me]... and during the month she was gone, it was totally rewritten in a form that looked like an operating system, with tools that were sort of known, you know, assembler, editor, and shell -- if not maintaining itself, right on the verge of maintaining itself, to totally sever the GECOS [= General Electric Comprehensive Operating System, a clone of System/360 DOS] connection. ... Yeh, essentially one person for a month.
It didn't exist by itself for very long ... maybe a day or two before we started developing the things we needed.

While Multics certainly influenced UNIX, there were also profound differences.

Dennis Ritchie explained:

We were a bit oppressed by the big system mentality. Ken wanted to do something simple. Presumably, as important as anything was the simple fact that our means were much smaller -- we could get only small machines with none of the fancy Multics hardware.
So UNIX wasn't quite a reaction against Multics, it was more a combination of these things. Multics wasn't there for us any more, but we liked the feel of interactive computing that it offered; Ken had some ideas about how to do a system that he had to work out; and the hardware available as well as our inclinations tended to trying to build neat small things, instead of grandiose ones.

Thompson "scarfed up" a PDP-7 and "did this neat stuff with it," Ritchie told me, modestly. Thompson created a new toy that would initiate work on a new system all over the world.

Soon a PDP-11 was acquired and UNIX was rewritten and expanded and rewritten. With McIlroy prodding, Dennis and Ken produced a UNIX Programmer's Manual (dated "November 3, 1971"). A "Second Edition" was issued June 12, 1972: "the number of Unix installations has grown to 10, with more expected," the Preface told us. Third Edition of the manual appeared "February, 1973," and noted that there were "now 16 installations." That was soon to wax quite rapidly.

All of the first 10 installations were at AT&T in New Jersey. In the late summer of 1972, UNIX leaped across the Hudson River to an office on the 14th floor of 330 Madison Avenue in Manhattan. Neil Groundwater had joined New York Telephone upon graduating from Penn State. He commuted from his apartment in Manhattan to Whippany, NJ., where he worked on programming for the Electronic Switching System. But being in Whippany placed him in proximity to Bell Labs and he began learning about UNIX. It was no easy task. "There was documentation on some parts," he told me. "But as we would come to say years later, 'Use the source, Luke' was the sole answer to many questions."3

In October 1973, Dennis Ritchie and Ken Thompson drove up the Hudson Valley to the new IBM Research Center at Yorktown Heights to deliver the first UNIX paper at the Symposium on Operating System Principles.

"It was a beautiful fall day," Dennis remarked. Ken, who delivered the paper, told me: "The audience was several hundred. I was pretty nervous. The response was the normal, polite applause. I don't recall any questions."

Ken was over-modest. The audience was quite enthusiastic. Ken and Dennis were immediately asked for copies of the new system.

This put the AT&T lawyers in a bind: was a computer operating system part of "common carrier communications services"? Was AT&T required to distribute UNIX?

The decision of the corporate lawyers was that Bell Labs should distribute UNIX to academic and research institutions at the cost of the media involved plus a shipping charge. Within a few months, several dozen institutions requested UNIX.