From mboxrd@z Thu Jan 1 00:00:00 1970 From: paul.winalski@gmail.com (Paul Winalski) Date: Fri, 29 Dec 2017 14:28:06 -0500 Subject: [TUHS] origin of C header files In-Reply-To: References: Message-ID: On 12/29/17, Wesley Parish 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.