On Fri, Dec 29, 2017 at 2:28 PM, Paul Winalski <paul.winalski@gmail.com> wrote:

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.

I'll +1 Paul's comment and add a couple of observations. Languages such a PL/1 and FORTRAN would could support a preprocessor and conditional compilation, were more easy to use to build 'products' - as opposed to Pascal. Folks did splice an backwards conditional compiling scheme with include files into some Pascal flavors but it was non-standard.

Fortran folks used tools like RATFOR or m4, but the key was the there was some why to preprocess code for different targets. In a production shop, particularly where your 'target' customer was different, this ability becomes more and more of an requirement.

I've always said as contemporary production systems programming languages, while BLISS had a better Macro system then C, the include file and conditional scheme worked much better/was much cleaner - to the point that ifdef is abused and the cause of much pain in actual code. But the truth is that is a success problem. When used properly, the C header scheme, while not invented by the BTL crew, was pretty much what people needed. No too fancy, but all the features you really needed and has been lasting.

Clem