steve@wlbr.UUCP (Steve Childress) (01/20/86)
The term "BCPL" is used frequently in the Developer's manuals and here
on the net. Other than seeing the shifted pointers called BPTR's, I
would appreciate an explanation of what this is all about. Is this all
Sun-related?
Also- Someone commented about device drivers must "be BCPL code".
Can someone clarify?
Regards,
Steve Childress
{trwrb, scgvaxd, ihnp4, voder, vortex} !wlbr!steve
or ...wlbr!wlbreng1!stevemykes@3comvax.UUCP (Mike Schwartz) (01/22/86)
BCPL stands for the "Before 'C' Programming Language", and was developed for the PDP-11 many years ago by the folks who brought us UNIX (Ken Thompson, et al). I believe you can read more in The 'C' Programming Language.
david@ukma.UUCP (David Herron, NPR Lover) (01/24/86)
In article <376@3comvax.UUCP> mykes@3comvax.UUCP (Mike Schwartz) writes: > >BCPL stands for the "Before 'C' Programming Language", and was developed >for the PDP-11 many years ago by the folks who brought us UNIX (Ken Thompson, >et al). I believe you can read more in The 'C' Programming Language. uuuuhhhh..... My book on BCPL says it stands for Basic CPL. It doesn't say much about CPL except it was invented at some british university. Other than that, you are pretty much correct. Enough so that nobody knows for sure which comes after C++, D or P. I vote for P. -- David Herron, cbosgd!ukma!david, david@UKMA.BITNET, soon, david@uky.csnet. Experience is something you don't get until just after you need it.
felsenst@entropy.UUCP (01/25/86)
Expires:
Sender:
Followup-To:
I believe BCPL stands for the Basic Cambridge Programming Language,
developed at Cambridge University in England. It is the ancestor of
C and is widely used in Britain to do things that are done in the
U. S. in C. In 'The C Programming Language' Kernighan and Ritchie
credit BCPL to Martin Richards and say that its influence on C was
through a language written by Ken Thompson, based on BCPL, and called
B. B's successor was called C. That is why C is called C.
Joe Felsenstein, Dept. Genetics, University
of Washington, Seattle
( ... uw-beaver!entropy!uw-evolution!joe)jmg@cernvax.UUCP (jmg) (01/27/86)
In article <410@wlbr.UUCP> steve@wlbr.UUCP writes: >The term "BCPL" is used frequently in the Developer's manuals and here >on the net. Other than seeing the shifted pointers called BPTR's, I >would appreciate an explanation of what this is all about. Is this all >Sun-related? > >Also- Someone commented about device drivers must "be BCPL code". >Can someone clarify? In the beginning was CPL: Cambridge (later Combined) Programming Language. It was invented by people at Cambridge and London Universities. It was so all-embracing that practically anything was allowed. Martin Richards, of Cambridge University, cut it down to size as BCPL: the B stands for Basic. It is like C in many respects, but has no types at all, merely the concept of a word as the unit. Martin used it to write a simple machine-independent operating system called Tripos, which Metacomco (I think) used as the basis for the Amiga OS. I do not think it is directly related to B, which was a predecessor of C.
danny@calgary.UUCP (Danny Levinson) (01/30/86)
C was indeed derived from BCPL, via an intermediate language B. I believe this heritage is mentioned in "The C programming language" (Kernighan & Ritchie). The process of derivation seems to have been: 1) take out all the syntactic & semantic "cleanliness" of BCPL (unless, repeat, repeatwhile, endcase, valof..resultis clauses, mandatory initialisations) 2) add types in a half-hearted manner (no control over precision), including a horrendous syntax for pointer declaration 3) hide the "OCODE" (machine independent intermediate object code) interface, making the language infinitely more difficult to port Of course, there are nice things about C too, such as the fact that Unix was written in it! -- danny levinson university of calgary
mwm%ucbopal@BERKELEY.EDU@caip.RUTGERS.EDU (01/30/86)
From: Mike (I'll be mellow when I'm dead) Meyer <mwm%ucbopal@BERKELEY.EDU> Since there weren't smiley faces plastered all over this, I'll assume he was serious and correct it (actually, giving credit to X for Y's work is bad news, and I would probably correct that even if it *had* smiley faces on it!). > BCPL stands for the "Before 'C' Programming Language", and was developed > for the PDP-11 many years ago by the folks who brought us UNIX (Ken > Thompson, et al). I believe you can read more in The 'C' Programming > Language. From the forward to "BCPL the language and its compiler" by Martin Richards and Colin Whitby-Strevens (Cambridge University Press, 1980): "BCPL was designed by one of the authors in 1967 (Richards)." BCLP stands for Basic CPL. BCPL is a stripped-down version of CPL (CPL stands for Combinded Programming Language). It was the inspiration/model/parent-of for B, which was designed by Dennis Ritchie and used for the utilities in early Unix systems (among other things). B grew up to become C, the early stages of which can also be blamed on Ritchie (ok, ok "for which Ritchie should also get credit".) This is the source of the "next language will be either B or P" comment in "The C Programming Language." [What we actually got was "C++", which, as the name implies, changes the language but has the same value (thank you, uokvax!jejones :-).] BCPL is *odd*. It's the only language I've ever seen that let's you change the value of a subroutine, like so: x() // call x x = x + 16 // add 16 to x x() // call (old x) + 16.... (x+16)() // Now call (old x) + 32.... It does have some of nice features that I wish had made it into C. resultis "Hack, Hack", <mike
milazzo@Rice.EDU@caip.RUTGERS.EDU (01/30/86)
From: Paul Milazzo <milazzo@Rice.EDU> Mike Schwartz <mykes@3comvax.UUCP> writes: >BCPL stands for the "Before 'C' Programming Language", and was developed >for the PDP-11 many years ago by the folks who brought us UNIX (Ken Thompson, >et al). I believe you can read more in The 'C' Programming Language. Actually, BCPL stands for Basic Combined Programming Language. BCPL was designed in 1967 by Martin Richards of Cambridge. One very good reference on BCPL is: BCPL, the language and its compiler Martin Richards and Colin Whitby-Strevens Cambridge University Press, 1979 QA76.73.B17R5 ISBN 0 521 21965 5 The first paragraph of Chapter 1 of this work gives an excellent summary of the history and purpose of BCPL: The language BCPL (Basic CPL) was originally developed as a compiler-writing tool and, as its name suggests, is closely related to CPL (Combined Programming Language) which was jointly developed at Cambridge and London Universities. CPL is described in Barron et al.[1]. BCPL adopted much of the syntactic richness of CPL, and strives for the same high standard of linguistic elegance; however, in order to achieve the efficiency necessary for systems-programming, its scale and complexity is far less than that of CPL. The most significant simplification is that BCPL has only one data type -- the bit-pattern -- and this feature alone gives it a characteristic flavour which is quite different from that of CPL and most other current programming languages. [1] Barron, D. W., Buxton, J. N., Hartley, D. F., Nixon, E. and Strachey, C. The main features of CPL. Computer Journal, vol. 6, p. 134 (1963). Richards and Whitby-Strevens go on to describe the language, the standard libraries, debugging facilities, and finally the compiler and its intermediate representations. Designed to be portable, the BCPL compiler is itself written in BCPL, and the book includes the entire source to the compiler front end as a "large example". I strongly recommend this book to anyone interested in learning more about BCPL. A former BCPL hacker, Paul G. Milazzo Dept. of Computer Science Rice University, Houston, TX Domain: milazzo@rice.EDU ARPA: milazzo@rice.ARPA BITNET: milazzo@ricenet, milazzo@ricecsvm UUCP: {cbosgd,convex,hp-pcd,shell,sun,waltz}!rice!milazzo
iwm@icdoc.UUCP (01/31/86)
In article <376@3comvax.UUCP> mykes@3comvax.UUCP (Mike Schwartz) writes: > >BCPL stands for the "Before 'C' Programming Language", and was developed >for the PDP-11 many years ago by the folks who brought us UNIX (Ken Thompson, >et al). I believe you can read more in The 'C' Programming Language. Well no - it stands for Basic CPL (CPL was Combined Programming Language, which came somewhere between ALGOL 60 and ALGOL 68. It was designed and implemented by Martin Richards at Cambridge (UK) in 1967. The line of languages is BCPL => B => C. -- Ian W Moor UUCP: seismo!mcvax!ukc!icdoc!iwm ARPA: iwm%icdoc@ucl Department of Computing Whereat a great and far-off voice was heard, saying, Imperial College. Poop-poop-poopy, and it was even so; and the days 180 Queensgate of Poopy Panda were long in the land. London SW7 Uk.
hamilton@uiucuxc.CSO.UIUC.EDU (01/31/86)
re: BCPL now, can somebody explain to me the utility of these #$%^@ shifted pointers? i can see how they would serve to enforce boundary alignment of certain structures in memory, but does this justify the contortions required? or is it some kind of vestige of pdp11's with 18-bit(?) physical addresses and 16-bit words? wayne hamilton
mykes@3comvax.UUCP (Mike Schwartz) (02/01/86)
did someone ask for a smiley face? . --------- . / \ . | o o | . | | . | \ / | . | ----- | . \ / . --------- give me a break, it's my first one. I guess humor is lost on some people. BCPL truly was the Before C Programming Language, wasn't it? I read about it in the 'C' Programming Language by B.W. Kernighan and D. Ritchie (mine's about 10 years old now) in the introduction. I'm a poet, I didn't know it, But my feet show it, They're long fellows. (you can't flame me, I'm waterproof) -
breuel@h-sc1.UUCP (02/04/86)
> now, can somebody explain to me the utility of these #$%^@ shifted pointers? > i can see how they would serve to enforce boundary alignment of certain > structures in memory, but does this justify the contortions required? > or is it some kind of vestige of pdp11's with 18-bit(?) physical addresses > and 16-bit words? The reason is very simple: since the language does not have data types, this is the only way that pointer arithmetic can work in a reasonably portable manner (i.e. without having to clutter your code with constants or special functions to do arithmetic). Furthermore, this happens to work extremely well on architectures on which the smallest addressable unit of memory is the word. Thomas. PS: needless to say, it has nothing whatsoever to do with PDP's in particular. You might, at most, say that it has something to do with DEC 10's, since they are in some sense word addressable, but whether this had any influence on the development of BCPL, I don't know.
radford@calgary.UUCP (Radford Neal) (02/05/86)
> re: BCPL > > now, can somebody explain to me the utility of these #$%^@ shifted pointers? I take it you're refering to the likely habit of a PDP11, VAX, 68000, etc. BCPL compiler to shift all pointers left one (maybe two) bits before use? This is purely a vestige of non-byte-addressable machines. A BCPL program will assume that if 'p' point to an integer array element, then 'p+1' will point to the next array element. This is part of the model of the machine assumed by the language. Since the compiler doesn't know that 'p' is a pointer to an integer (or even a pointer at all, if I recall correctly), it must really add just 1, not 2 or 4 like a C compiler would. The only way to get this to work is to shift the pointer on dereference. The problem doesn't arise on old machines with only one size of addressable storage unit. This problem is, of course, the reason for C having typed pointers and doing stride adjustment as part of pointer arithmetic. Radford Neal