[TUHS] origin of C header files

Paul Winalski paul.winalski at gmail.com
Sat Dec 30 05:28:06 AEST 2017

On 12/29/17, 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?

It probably all started with macro-instructions (macros) in assembly
languages.  The assembler for System/360 in the 1960s had a pretty
complex and powerful conditional assembly and macro expansion
capability.  That technology I'm sure dates back to the 1950s.

When higher-level languages came along, programmers moving from
assembly code to a HLL would want the same sort of preprocessor
functionality.  I know that IBM PL/I had %include, and I suspect that
other HLLs of the day had similar features.

What's very clear is that C did not invent include files or
conditional compilation, it merely carried on existing tradition.

-Paul W.

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