[TUHS] origin of C header files

[Nigel Williams]

On Fri, Dec 29, 2017 at 7:26 PM, Wesley Parish <wobblygong at gmail.com> wrote:
> Which raised the question: when did header files come into use? Who
> was the first to use header files to store common system-wide or
> application-wide data definitions? Was it used in any languages prior
> to C?

COBOL 60 (April 1960) had INCLUDE (page V-27):

http://bitsavers.trailing-edge.com/pdf/codasyl/COBOL_Report_Apr60.pdf

FUNCTION: To save the programmer effort by automatically incorporating
          library subroutines into the source program.

It even had a literal substitution mechanism to rewrite the included text.