....
- CMU's ALGOL68S from 1978 list all these ways --
co comment
comment comment
pr pragmat
pragmat pragmat
# (comment symbol) comment
:: (pragmat symbol) pragmat
(its for UNIX v6 or v7 so not surprising # is a comment)
http://www.softwarepreservation.org/projects/ALGOL/manual/a68s.txt/view
Be careful of overthinking here. The comment in that note says was it was for PDP-11's and lists V6 and V7 was a possible target, but it did not say it was. Also, the Speach and Vision PDP-11/40e based systems ran a very hacked v6 (which a special C compiler that supported CMU's csv/cret instructions in the microcode), which would have been the target systems. [1]
To my knowledge/memory, the CMU Algol68 compiler never ran anywhere but Hydra (and also used custom microcode). IIRC there was some talk to move it to *OS (Star OS for CM*) I've sent a note to dvk to see if he remembers it otherwise. I also ask Liebensperger what he remembers, he was hacking on *OS in those days. Again, IIRC Prof. Peter Hibbard was the mastermind behind the CMU Algol68 system. He was a Brit from Cambridge (and taught the parallel computing course which I took from him at the time).
FWIW: I also don't think the CMU Algol68 compiler was ever completely self-hosting, and like BLISS, required the PDP-10 to support it. As to why it was not moved to the Vax, I was leaving/had left by that time, but I suspect the students involved graduated and by then the Perq's had become the hot machine for language types and ADA would start being what the gvt would give research $s too.
...
But look! The very first line of that file! It is a single # sitting all by itself. Why? you ask. Well this is a hold over from when the C preprocessor was new. C orginally did not have it and was added later. PL/I had a %INCLUDE so Ritchie eventaully made a #include -- but pre 7th Edition the C preprocessor would not be inkoved unless the very first character of the C source file was an #
That was true of V7 and Typesetter C too. It was a separate program (/lib/cpp) that the cc command called if needed.
Since v7 the preprocessor always run on it. The first C preprocessor was Ritchie's work with no nested includes and no macros. v7's was by John Reiser which added those parts.
Right, this is what I was referring too last night in reference to Sean comments. As I said, the /bin/cc command was a shell script and it peaked at the first character to see if it was #. I still find myself starting all C programs with a # on a line by itself ;-)
Note that the Ritchie cpp was influenced by Brian's Ratfor work, so using # is not surprising.
This leads to a question/thought for this group, although I think needs to move to COFF (which I have CC'ed for follow up).
I have often contended, that one of the reasons why C, Fortran, and PL/1 were so popular as commercial production languages were because they could be preprocessed. For a commercial place where lots of different targets is possible, that was hugely important. Pascal, for instance, has semantics that makes writing a preprocessor like cpp or Ratfor difficult (which was one of the things Brian talks about in his "Why Pascal is not my favorite Programming Language" paper). [2]
So, if you went to commercial ISV's and looked at what they wrote in. It was usually some sort of preprocessed language. Some used Ratfor like a number of commercial HPC apps vendors, Tektronix wrote PLOT10 in MORTRAN. I believe it was Morgan-Stanley had a front-end for PL/1, which I can not recall the name. But you get the point ... if you had to target different runtime environments, it was best for your base code to not be specific.
However ... as C became the system programming language, the preprocessor was important. In fact, it even gave birth the other tools like autoconfig to help control them. Simply, the idiom:
#ifdef SYSTEMX
#define SOME_VAR (1)
... do something specific
#endif /* SYSTEMX */
While loathsome to read, it actually worked well in practice.
That fact is I hate the preprocessor in many ways but love it for what it for the freedom it actually gave us to move code. Having programmed since the 1960s, I remember how hard it was to move things, even if the language was the same.
Today, modern languages try to forego the preprocessor. C++'s solution is to throw the kitchen sink into the language and have 'frameworks', none of which work together. Java's and its family tries to control it with the JVM. Go is a little too new to see if its going to work (I don't see a lot of production ISV code in it yet).
Note: A difference between then and now, is 1) we have few target architectures and 2) we have fewer target operating environments, 3) ISV don't like multiple different versions of their SW, they much prefer very few for maintenance reasons so they like # 1 and #2 [i.e. Cole's law of economics in operation here].
So ... my question, particularly for those like Doug who have programmed longer and at least as long as I, what do you think? You lived the same time I did and know the difficulties we faced. Is the loss of a preprocessor good or bad?
Clem
[1] Historical footnote about CMU. I was the person that brought V7 into CMU and I never updated the Speach or Vision systems and I don't think anyone did after I left. We ran a CMU V7 variant mostly on the 11/34s (and later on a couple of 11/44s I believe) that had started to pop up. Although later if it was a DEC system, CS was moving to Vaxen when they could get the $s (but the Alto's and Perq's had become popular with the CMU SPICE proposal). Departments like bio-engineering, mech ee, ran the cheaper systems on-site and then networked over the Computer Center's Vaxen and PDP-20's when they needed address space).
[2] Note: Knuth wrote "Web" to handle a number of the issues, Kernighan talks about - but he had to use an extended Pascal superset and his program was notable for not being portable (he wrote for it for the PDP-10 Pascal). [BTW: Ward Cunningham, TW Cook and I once counted over 8 different 'Tek Pascal' variants and 14 different 'HP Basics'].