[TUHS] origin of C header files

[Wesley Parish]

Hi

I've just had an interesting experience, explaining C header files to
a nephew programmer who didn't understand them. I pointed him in the
direction of Minix as an example of a small well-engineered system
which would display their use.

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?

Thanks

Wesley Parish