Re: Why is Cobol ignored in compiler textbooks?

geoff@world.std.com (Geoff Collyer) writes:


>>Also, the _problem_ of the ALTER verb changing the target of a GO TO.
>Unless my memory is really playing tricks, this has been a non-problem for
>years. The 1974 COBOL standard deleted ALTER, as I recall. Even then, it
>was recognised as a botch.


ALTER is definitely still in COBOL-74.


However, I don't know of a single organisation that employs Cobol
programmers that doesn't also have programming standards that explicitly
*forbid* it's use. As a consequence most production Cobol compilers have a
"NO-ALTER" directive that both enforces this prohibition and enables the
compiler to make reasonable attempts to optimise the code.


Actually I *think* that ALTER is even still in COBOL-85 although it is now
obsolescent and will disappear completely from the next version of the
standard.


Interesting piece of trivia is that Cobol segmentation ceases to be
"interesting" once ALTER disappears from the standard since the semantics
of Cobol segmentation are all concerned with the behaviour of ALTER-ed GO
TO statements in the overlay segments ....
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