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C(7)               FreeBSD Miscellaneous Information Manual               C(7)

     c, c78, c89, c90, c99 - The C programming language

     C is a general purpose programming language, which has a strong
     connection with the UNIX operating system and its derivatives, since the
     vast majority of those systems were written in the C language.  The C
     language contains some basic ideas from the BCPL language through the B
     language written by Ken Thompson in 1970 for the DEC PDP-7 machines.  The
     development of the UNIX operating system was started on a PDP-7 machine
     in assembly language, but it made very difficult to port the existing
     code to other systems.

     In 1972 Dennis M. Ritchie worked out the C programming language for
     further development of the UNIX operating system.  The idea was to
     implement only the C compiler for different platforms, and implement most
     part of the operating system in the new programming language to simplify
     the portability between different architectures.  It follows that C is
     very eligible for (but not limited to) writing operating systems and low-
     level applications.

     The C language did not have a specification or standardized version for a
     long time.  It went through a lot of changes and improvements for ages.
     In 1978, Brian W. Kernighan and Dennis M. Ritchie published the first
     book about C under the title "The C Programming Language".  We can think
     of this book as the first specification of the language.  This version is
     often referred as K&R C after the names of the authors.  Sometimes it is
     referred as C78, as well, after the publishing year of the first edition
     of the book.

     It is important to notice, that the instruction set of the language is
     limited to the most fundamental elements for simplicity.  Handling of the
     standard I/O and such common functions are implemented in the libraries
     shipped with the compiler.  As these functions are also widely used, it
     was demanded to include into the description what requisites the library
     should conform to, not just strictly the language itself.  Accordingly,
     the aforementioned standards cover the library elements, as well.  The
     elements of this standard library is still not enough for more
     complicated tasks.  In this case the provided system calls of the given
     operating system can be used.  To not lose the portability by using these
     system calls, the POSIX (Portable Operating System Interface) standard
     evolved.  It describes what functions should be available to keep
     portability.  Note, that POSIX is not a C standard, but an operating
     system standard and thus is beyond the scope of this manual.  The
     standards discussed below are all C standards and only cover the C
     programming language and the accompanying library.

     After the publication of the book mentioned before, the American National
     Standards Institute (ANSI) started to work on standardizing the language,
     and they announced ANSI X3.159-1989 in 1989.  It is usually referred as
     ANSI C or C89.  The main difference in this standard were the function
     prototypes, which is a new way of declaring functions.  With the old-
     style function declarations, the compiler was unable to check the sanity
     of the actual parameters at a function call.  The old syntax was highly
     error-prone because incompatible parameters were hard to detect in the
     program code and the problem only showed up at run-time.

     In 1990, the International Organization for Standardization (ISO) adopted
     the ANSI standard as ISO/IEC 9899:1990 in 1990.  This is also referred as
     ISO C or C90.  It only contains negligible minor modifications against
     ANSI C, so the two standards often considered to be fully equivalent.
     This was a very important milestone in the history of the C language, but
     the development of the language did not stop.

     The ISO C standard was later extended with an amendment as ISO/IEC 9899
     AM1 in 1995.  This contained, for example, the wide-character support in
     wchar.h and wctype.h.  Two corrigenda were also published: Technical
     Corrigendum 1 as ISO/IEC 9899 TCOR1 in 1995 and Technical Corrigendum 2
     as ISO/IEC 9899 TCOR1 in 1996.  The continuous development and growth
     made it necessary to work out a new standard, which contains the new
     features and fixes the known defects and deficiencies of the language.
     As a result, ISO/IEC 9899:1999 was born in 1999.  Similarly to the other
     standards, this is referred after the publication year as C99.  The
     improvements include the following:

              Inline functions

              Support for variable length arrays

              New high-precision integer type named long long int, and other
               integer types defined in stdint.h

              New boolean data type implemented in stdbool.h

              One line comments taken from the C++ language

              Some new preprocessor features

              New variables can be declared anywhere, not just in the
               beginning of the program or program blocks

              No implicit int type

     Since then new standards have not been published, but the C language is
     still evolving.  New and useful features have been showed up in the most
     famous C compiler: GNU C.  Most of the UNIX-like operating systems use
     GNU C as a system compiler, but those addition in GNU C should not be
     considered as standard features.

     c89(1), c99(1), cc(1)

     ANSI, X3.159-1989.

     ISO/IEC, 9899:1990, Programming languages -- C.

     ISO/IEC, 9899 AM1.

     ISO/IEC, 9899 TCOR1, Programming languages -- C, Technical Corrigendum 1.

     ISO/IEC, 9899 TCOR2, Programming languages -- C, Technical Corrigendum 2.

     ISO/IEC, 9899:1999, Programming languages -- C.

     This manual page first appeared in FreeBSD 9.0.

     This manual page was originally written by Gabor Kovesdan
     <[email protected]>.

FreeBSD 11.1-RELEASE-p4          May 30, 2011          FreeBSD 11.1-RELEASE-p4
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