184 lines
7.0 KiB
Groff
184 lines
7.0 KiB
Groff
.\" Copyright (C) 2007, 2010 Gabor Kovesdan. All rights reserved.
|
|
.\"
|
|
.\" Redistribution and use in source and binary forms, with or without
|
|
.\" modification, are permitted provided that the following conditions
|
|
.\" are met:
|
|
.\" 1. Redistributions of source code must retain the above copyright
|
|
.\" notice, this list of conditions and the following disclaimer.
|
|
.\" 2. Redistributions in binary form must reproduce the above copyright
|
|
.\" notice, this list of conditions and the following disclaimer in the
|
|
.\" documentation and/or other materials provided with the distribution.
|
|
.\"
|
|
.\" THIS SOFTWARE IS PROVIDED BY AUTHOR AND CONTRIBUTORS ``AS IS'' AND
|
|
.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
|
|
.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
|
|
.\" ARE DISCLAIMED. IN NO EVENT SHALL AUTHOR OR CONTRIBUTORS BE LIABLE
|
|
.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
|
|
.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
|
|
.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
|
|
.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
|
|
.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
|
|
.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
|
|
.\" SUCH DAMAGE.
|
|
.\"
|
|
.\" $FreeBSD$
|
|
.\"
|
|
.Dd May 30, 2011
|
|
.Dt C 7
|
|
.Os
|
|
.Sh NAME
|
|
.Nm c, c78, c89, c90, c99
|
|
.Nd The C programming language
|
|
.Sh DESCRIPTION
|
|
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.
|
|
.Pp
|
|
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.
|
|
.Pp
|
|
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.
|
|
.Pp
|
|
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.
|
|
.Pp
|
|
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.
|
|
.Pp
|
|
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.
|
|
.Pp
|
|
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:
|
|
.Bl -bullet -offset indent
|
|
.It
|
|
Inline functions
|
|
.It
|
|
Support for variable length arrays
|
|
.It
|
|
New high-precision integer type named long long int, and other integer types
|
|
defined in stdint.h
|
|
.It
|
|
New boolean data type implemented in stdbool.h
|
|
.It
|
|
One line comments taken from the C++ language
|
|
.It
|
|
Some new preprocessor features
|
|
.It
|
|
New variables can be declared anywhere, not just in the beginning of the
|
|
program or program blocks
|
|
.It
|
|
No implicit int type
|
|
.El
|
|
.Pp
|
|
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.
|
|
.Sh SEE ALSO
|
|
.Xr c89 1 ,
|
|
.Xr c99 1 ,
|
|
.Xr cc 1
|
|
.Sh STANDARDS
|
|
.Rs
|
|
.%A ANSI
|
|
.%T X3.159-1989
|
|
.Re
|
|
.Pp
|
|
.Rs
|
|
.%A ISO/IEC
|
|
.%T 9899:1990, Programming languages -- C
|
|
.Re
|
|
.Pp
|
|
.Rs
|
|
.%A ISO/IEC
|
|
.%T 9899 AM1
|
|
.Re
|
|
.Pp
|
|
.Rs
|
|
.%A ISO/IEC
|
|
.%T 9899 TCOR1, Programming languages -- C, Technical Corrigendum 1
|
|
.Re
|
|
.Pp
|
|
.Rs
|
|
.%A ISO/IEC
|
|
.%T 9899 TCOR2, Programming languages -- C, Technical Corrigendum 2
|
|
.Re
|
|
.Pp
|
|
.Rs
|
|
.%A ISO/IEC
|
|
.%T 9899:1999, Programming languages -- C
|
|
.Re
|
|
.Sh HISTORY
|
|
This manual page first appeared in
|
|
.Fx 9.0 .
|
|
.Sh AUTHORS
|
|
This manual page was originally written by
|
|
.An Gabor Kovesdan Aq Mt gabor@FreeBSD.org .
|