On Mon, 31 Aug 2020 16:57:22 -0000 (UTC), Martin Gregorie
 declaimed the following:

>Early COBOLs would allow you to call assembler subroutines but the
>language did not allow external subroutines to be written in COBOL. I
>don't remember seeing this feature in any implementation before 1978.
>

 I'm pretty certain the COBOL-74 standard provided for external modules
to be linked -- my Xerox Sigma-6 manual is in storage so I can't confirm --
and it has been 45 years since I took that class.
https://en.wikipedia.org/wiki/COBOL#COBOL-68
"""
COBOL-74 added subprograms, giving programmers the ability to control the
data each part of the program could access.
"""

>Early COBOLs also required a program to be a single source file though it
>had a COPY statement that could be used to pull in record definitions or
>sections of code. Fortunately, the compilers could handle huge source
>files: a program of less then 200 lines usually did nothing useful.
>Programs were generally in the 1000-4000 line range though I have seen a
>few in the 10,000 line range.

 Strangely, while I'm sure my course introduced linking separately
compiled COBOL modules, we were NOT introduced to "COPY" statements.

>
>There was a built-in Y2K gotcha too: The only way you could get hold of
>the date was with a statement like
>
> ACCEPT DATE-TODAY FROM SYSTEM-DATE.
>
>where the DATE-TODAY variable *had* to be declared in working storage as:
>
>  01 DATE-TODAY      PIC 9(6).
>
>and the ACCEPT statement would fill it with a date formatted as 'yymmdd'.
>This requirement was defined in the CODASYL Report (i.e. was part of the
>language standard) and AFAIK it was not changed until after Y2K had been
>and gone.

 Though that is a minor problem -- since it returns the current date, it
at least was easy to detect century wrap-around and preface with the
correct 19 or 20.

 Not so simple is the case of data records that could span a range where
"windowing" was not feasible.


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