1. 18
  1. 2

    What year for each?

    1. 7

      Tuhs.org’s Unix Tree provides one convenient set of dates to look at. According to it, the dates are Research V3 1973-02, V4 1973-11, V5 1974-06, V6 1975-05, and then V7 1979-01. System III is 1980-06, and in the BSD series 4BSD 1980-10, 4.2BSD 1983-09 and 4.3BSD 1986-06. I don’t know offhand when POSIX standardized its various named signals, but POSIX itself dates from 1988.

      (I’m the author of the linked-to article.)

    2. 1

      One thing that surprised me about the article is that it doesn’t contain any dates! The first set of twelve signals that the author mentions appears to date to 1973-08-05:

       1	hangup
       2	interrupt
       3	quit
       4	illegal instruction
       5	trace trap
       6	IOT instruction
       7	EMT instruction
       8	floating point exception
       9	kill (cannot be caught or ignored)
      10	bus error
      11	segmentation violation
      12	bad argument to sys call