A History of the C Languages

1. A History of the C Languages By: Kevin Burnette

2. Outline • History • Ancestor languages overview • Development of C • Development of C++

3. Where it all began • Combined Programming Language – CPL • Basic Combined Programming Language – BCPL • B

4. What’s new in B • += and -= operators were introduced to the language • ++ and -- operators were invented.

5. From B to C • New B - NB • Dennis Ritchie of Bell Labs created an extend version of B in 1971. • Added int, and char types, arrays of them and pointers to them and rewrote the compiler to create PDP-11 instructions. • NB created programs small and fast enough to compete with assembly written programs.

6. Questions of design • These questions were asked in designing structure types. • “Where could the compiler hide the pointer to name that the semantics demanded?” (Ritchie 8) • “Even if structures were thought of more abstractly, and the space for pointers could be hidden somehow, how could I handle the technical problem of properly initializing these pointers when allocating a complicated object, perhaps one that specified structures containing arrays containing structures to arbitrary depth?” (Ritchie 8)

7. Answer: • The solution eliminated the materialization of the pointer in storage, and instead caused the creation of the pointer when the array name is mentioned in an expression. • This provided a large jump in the evolution between typeless BCPL and C.

8. More Innovation – Type Structure “The central notion I captured from Algol was a type structure based on atomic types (including structures), composed into arrays, pointers (references), and functions (procedures).” (Ritchie 8)

9. C is officially born • “After creating the type system, the associated syntax, and the compiler for the new language, I felt that it deserved a new name; NB seemed insufficiently distinctive. I decided to follow the single-letter style and called it C, leaving open the question whether the name represented a progression through the alphabet or through the letters in BCPL.” (Ritchie 9)

10. Further Development • Preprocessor • The preprocessor was originally added as an optional component • First version only provided file including and simple string replacement • Idea was taken from BCPL and PL/I

11. C with Classes • Work began in 1979 in attempt to analyze the UNIX kernel to see if it could be distributed over a network • Bjarne Stroustrup begin creating the tools he needed based on his experience with Simula

12. C++ • Between 1982 and 1984 Stroustrup began to think of C with Classes as a separate language instead of an addition to C. • Version 1.0 was released in 1985 and C++ was officially named.

13. Code Examples GET "LIBHDR" MANIFEST $( BOTTLES = 99 $) LET START() BE $( LET BEERS(N, S) BE $( TEST N = 0 THEN WRITEF("No more bottles") ELSE WRITEF("%N bottle%S", N, (N = 1) -> "", "s") WRITEF(" of beer%S", S) $) FOR I = BOTTLES TO 1 BY -1 DO $( BEERS(I, " on the wall, ") BEERS(I, ".*NTake one down, pass it around.*N") BEERS(I - 1, " on the wall.*N") $) FINISH $) From: http://www.99-bottles-of-beer.net/language-bcpl-85.html

14. Sources • “BCPL.” Wikipedia: The Free Encyclopedia. 2006. Wikipedia. 7 Apr 2006. http://en.wikipedia.org/wiki/BCPL • “Combined Programming Language.” Wikipedia: The Free Encyclopedia. 2006. Wikipedia. 7 Apr 2006. http://en.wikipedia.org/wiki/Combined_Programming_Language • Ritchie, Dennis. “The Development of the C Language.” History of Programming Languages-II. Ed. T.J. Bergin, Jr. and R. G. Gibson, Jr. ACM Press (New York) and Addison-Wesley (Reading, Mass), 1996; ISBN 0-201-89502-1. • Stroustrup, Bjarne. “A History of C++: 1979-1991.” History of Programming languages. Ed. T.J.Bergin and R.G. Gibson, Jr. ACM Press (New York) and Addison-Wesley (Reading, Mass), 1996; ISBN 0-201-89502-1.