This November, the Unix community has another notable anniversary to celebrate: the 40th birthday of the first edition of Ken Thompson and Dennis Ritchie's Unix Programmers Manual, released in November 1971. Producing the document was no easy task, because at that point the Unix operating system grew by the week; budding aficionados added new commands and features to the system on a regular basis.
"The rate of change of the system is so great that a dismayingly large number of early sections [of the text] had to be modified while the rest were being written," Thompson and Ritchie noted in their introduction. "The unbounded effort required to stay up-to-date is best indicated by the fact that several of the programs described were written specifically to aid in preparation of this manual!"
That's why Unix timelines are fun to read—they give a sense of how quickly the system collaboratively evolved. But some of them either skip or mention without explanation a government decision that, in retrospect, paved the way not only for Unix, but perhaps for the open source movement as well: the 1956 Consent Decree between the United States Department of Justice and AT&T.
That crucial decision didn't exactly force AT&T to share Unix with the world, but it made the decision much easier.
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