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1.12      jruoho     28: .Dd March 30, 2011
1.1       jruoho     29: .Dt C 7
                     30: .Os
                     31: .Sh NAME
                     32: .Nm c, c78, c89, c90, c99
                     33: .Nd The C programming language
                     34: .Sh DESCRIPTION
                     35: C is a general purpose programming language, which has a strong connection
                     36: with the UNIX operating system and its derivatives, since the vast
                     37: majority of those systems were written in the C language.
                     38: The C language contains some basic ideas from the BCPL language through
                     39: the B language written by Ken Thompson in 1970 for the DEC PDP-7 machines.
                     40: The development of the UNIX operating system was started on a PDP-7
1.6       wiz        41: machine in assembly language, but this choice made it very difficult
                     42: to port the existing code to other systems.
1.1       jruoho     43: .Pp
                     44: In 1972 Dennis M. Ritchie worked out the C programming language for
                     45: further development of the UNIX operating system.
                     46: The idea was to implement only the C compiler for different
1.6       wiz        47: platforms, and implement most parts of the operating system
1.1       jruoho     48: in the new programming language to simplify the portability between
                     49: different architectures.
1.6       wiz        50: It follows that C is very well adapted for (but not limited to) writing
1.1       jruoho     51: operating systems and low-level applications.
                     52: .Pp
                     53: The C language did not have a specification or standardized version for
                     54: a long time.
                     55: It went through a lot of changes and improvements for ages.
                     56: In 1978, Brian W. Kernighan and Dennis M. Ritchie published the
1.6       wiz        57: first book about C under the title
                     58: .Dq The C Programming Language .
1.1       jruoho     59: We can think of this book as the first specification of the language.
1.6       wiz        60: This version is often referred to as
                     61: .Dq K&R C
                     62: after the names of the authors.
                     63: Sometimes it is referred to as C78, as well, after the publishing year of
1.1       jruoho     64: the first edition of the book.
                     65: .Pp
1.6       wiz        66: It is important to notice that the instruction set of the language is
1.1       jruoho     67: limited to the most fundamental elements for simplicity.
1.6       wiz        68: Handling of the standard I/O and similar common functions are implemented in
1.1       jruoho     69: the libraries shipped with the compiler.
                     70: As these functions are also widely used, it was demanded to include into
                     71: the description what requisites the library should conform to, not just
                     72: strictly the language itself.
                     73: Accordingly, the aforementioned standards cover the library elements, as well.
1.6       wiz        74: The elements of this standard library are still not enough for more
1.1       jruoho     75: complicated tasks.
                     76: In this case the provided system calls of the given operating system can be
                     77: used.
1.6       wiz        78: To not lose the portability by using these system calls, the POSIX
                     79: (Portable Operating System Interface (for Unix)) standard evolved.
1.1       jruoho     80: It describes what functions should be available to keep portability.
                     81: Note, that POSIX is not a C standard, but an operating system standard
                     82: and thus is beyond the scope of this manual.
                     83: The standards discussed below are all C standards and only cover
                     84: the C programming language and the accompanying library.
                     85: .Pp
                     86: After the publication of the book mentioned before,
                     87: the American National Standards Institute (ANSI) started to work on
1.6       wiz        88: standardizing the language, and in 1989 they announced ANSI X3.159-1989.
                     89: It is usually referred to as ANSI C or C89.
1.1       jruoho     90: The main difference in this standard were the function prototypes,
1.6       wiz        91: which was a new way of declaring functions.
1.1       jruoho     92: With the old-style function declarations, the compiler was unable to
1.6       wiz        93: check the sanity of the actual parameters of a function call.
1.1       jruoho     94: The old syntax was highly error-prone because incompatible parameters
                     95: were hard to detect in the program code and the problem only showed up
                     96: at run-time.
                     97: .Pp
                     98: In 1990, the International Organization for Standardization (ISO) adopted
1.6       wiz        99: the ANSI standard as ISO/IEC 9899:1990.
                    100: This is also referred to as ISO C or C90.
1.1       jruoho    101: It only contains negligible minor modifications against ANSI C,
1.6       wiz       102: so the two standards are often considered to be fully equivalent.
1.1       jruoho    103: This was a very important milestone in the history of the C language, but the
                    104: development of the language did not stop.
                    105: .Pp
                    106: The ISO C standard was later extended with an amendment as
                    107: ISO/IEC 9899 AM1 in 1995.
                    108: This contained, for example, the wide-character support in wchar.h and
                    109: wctype.h.
1.6       wiz       110: Two corrigenda were also published: Technical Corrigendum 1 as
                    111: ISO/IEC 9899 TCOR1 in 1995 and Technical Corrigendum 2 as ISO/IEC 9899 TCOR2
1.1       jruoho    112: in 1996.
                    113: The continuous development and growth made it necessary to work out a new
                    114: standard, which contains the new features and fixes the known defects and
                    115: deficiencies of the language.
                    116: As a result, ISO/IEC 9899:1999 was born in 1999.
1.3       dholland  117: Similarly to the other standards, this is referred to after the
1.1       jruoho    118: publication year as C99.
                    119: The improvements include the following:
                    120: .Bl -bullet -offset indent
                    121: .It
1.5       jruoho    122: Inline functions.
1.1       jruoho    123: .It
1.5       jruoho    124: Support for variable length arrays.
1.1       jruoho    125: .It
1.5       jruoho    126: New high-precision integer type named
                    127: .Vt long long int ,
                    128: and other integer types described in
                    129: .Xr stdint 3
                    130: and
                    131: .Xr inttypes 3 .
1.1       jruoho    132: .It
1.5       jruoho    133: New boolean data type; see
                    134: .Xr stdbool 3 .
1.1       jruoho    135: .It
1.5       jruoho    136: One line comments taken from the C++ language.
1.1       jruoho    137: .It
1.5       jruoho    138: Some new preprocessor features.
1.1       jruoho    139: .It
1.9       jruoho    140: A predefined identifier
1.11      uwe       141: .Va __func__
1.9       jruoho    142: and a
1.11      uwe       143: .Vt restrict
1.9       jruoho    144: type qualifier.
                    145: .It
1.1       jruoho    146: New variables can be declared anywhere, not just in the beginning of the
1.5       jruoho    147: program or program blocks.
1.1       jruoho    148: .It
1.5       jruoho    149: No implicit
                    150: .Vt int
                    151: type.
1.1       jruoho    152: .El
                    153: .Pp
1.6       wiz       154: Since then no new standards have been published, but the C language is still
1.1       jruoho    155: evolving.
1.6       wiz       156: New and useful features have been showing up in the most famous
                    157: C compiler: GNU C
                    158: .Pq Xr gcc 1 .
1.1       jruoho    159: Most of the UNIX-like operating systems use GNU C as a system compiler,
1.8       jruoho    160: but the various extensions of GNU C, such as
1.10      jruoho    161: .Xr attribute 3
                    162: or
                    163: .Xr typeof 3 ,
1.8       jruoho    164: should not be considered standard features.
1.1       jruoho    165: .Sh SEE ALSO
                    166: .Xr c89 1 ,
1.6       wiz       167: .Xr c99 1 ,
1.12      jruoho    168: .Xr cc 1 ,
                    169: .Xr cdefs 3
1.1       jruoho    170: .Rs
                    171: .%A Brian W. Kernighan
                    172: .%A Dennis M. Ritchie
                    173: .%B The C Programming Language
                    174: .%D 1988
                    175: .%N Second Edition, 40th printing
                    176: .%I Prentice Hall
                    177: .Re
                    178: .Sh STANDARDS
                    179: .Rs
                    180: .%A ANSI
                    181: .%T X3.159-1989
                    182: .Re
                    183: .Pp
                    184: .Rs
                    185: .%A ISO/IEC
                    186: .%T 9899:1990, Programming languages -- C
                    187: .Re
                    188: .Pp
                    189: .Rs
                    190: .%A ISO/IEC
                    191: .%T 9899 AM1
                    192: .Re
                    193: .Pp
                    194: .Rs
                    195: .%A ISO/IEC
                    196: .%T 9899 TCOR1, Programming languages -- C, Technical Corrigendum 1
                    197: .Re
                    198: .Pp
                    199: .Rs
                    200: .%A ISO/IEC
                    201: .%T 9899 TCOR2, Programming languages -- C, Technical Corrigendum 2
                    202: .Re
                    203: .Pp
                    204: .Rs
                    205: .%A ISO/IEC
                    206: .%T 9899:1999, Programming languages -- C
                    207: .Re
1.7       jruoho    208: .Pp
                    209: .Rs
                    210: .%A ISO/IEC
                    211: .%T 9899:1999 TCOR1, Programming languages -- C, Technical Corrigendum 1
                    212: .Re
                    213: .Pp
                    214: .Rs
                    215: .%A ISO/IEC
                    216: .%T 9899:1999 TCOR2, Programming languages -- C, Technical Corrigendum 2
                    217: .Re
                    218: .Pp
                    219: .Rs
                    220: .%A ISO/IEC
                    221: .%T 9899:1999 TCOR3, Programming languages -- C, Technical Corrigendum 3
                    222: .Re
1.1       jruoho    223: .Sh HISTORY
                    224: This manual page first appeared in
                    225: .Fx 9.0
                    226: and
                    227: .Nx 6.0 .
                    228: .Sh AUTHORS
                    229: This manual page was written by
1.13      wiz       230: .An Gabor Kovesdan Aq Mt gabor@FreeBSD.org .

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