C alternative tokens refer to a set of alternative spellings of common operators in the
C programming language
''The C Programming Language'' (sometimes termed ''K&R'', after its authors' initials) is a computer programming book written by Brian Kernighan and Dennis Ritchie, the latter of whom originally designed and implemented the language, as well as ...
. They are implemented as a group of macro constants in the
C standard library
The C standard library or libc is the standard library for the C programming language, as specified in the ISO C standard.ISO/IEC (2018). '' ISO/IEC 9899:2018(E): Programming Languages - C §7'' Starting from the original ANSI C standard, it wa ...
in the
iso646.h header. The tokens were created by Bjarne Stroustrup for the pre-standard C++ language
and were added to the C standard in a 1995 amendment to the
C90 standard via library to avoid the breakage of existing code.
The alternative tokens allow programmers to use
C language
C (''pronounced like the letter c'') is a general-purpose computer programming language. It was created in the 1970s by Dennis Ritchie, and remains very widely used and influential. By design, C's features cleanly reflect the capabilities o ...
bitwise and logical
operators
Operator may refer to:
Mathematics
* A symbol indicating a mathematical operation
* Logical operator or logical connective in mathematical logic
* Operator (mathematics), mapping that acts on elements of a space to produce elements of another sp ...
which could otherwise be hard to type on some international and non-
QWERTY
QWERTY () is a keyboard layout for Latin-script alphabets. The name comes from the order of the first six Computer keyboard keys#Types, keys on the top left letter row of the keyboard ( ). The QWERTY design is based on a layout created f ...
keyboards. The name of the header file they are implemented in refers to the
ISO/IEC 646
ISO/IEC 646 is a set of ISO/IEC standards, described as ''Information technology — ISO 7-bit coded character set for information interchange'' and developed in cooperation with ASCII at least since 1964. Since its first edition in 1 ...
standard, a 7-bit character set with a number of regional variations, some of which have accented characters in place of the punctuation marks used by C operators.
The macros
The
iso646.h header defines the following 11 macros as stated below:
C++
The above-mentioned identifiers are
operator keywords in the
ISO C++ programming language and do not require the inclusion of a header file.
For consistency, the
C++98 C98 or C-98 may refer to:
* C-98 Clipper, the military designation of the Boeing 314 flying boat
* CJYC-FM, "Big John FM", formerly known as "C98"
* Cray C98, a model of the Cray C90
* Ruy Lopez (ECO code), a chess opening
* Lake Village Airport (F ...
standard provides the header
<ciso646>. However the latter file has no effect, being empty. Some compilers, such as
Microsoft Visual C++
Microsoft Visual C++ (MSVC) is a compiler for the C, C++ and C++/CX programming languages by Microsoft. MSVC is proprietary software; it was originally a standalone product but later became a part of Visual Studio and made available in both tria ...
have, at least in the past, required the header to be included in order to use these identifiers unless a compiler flag is set.
See also
*
Digraphs and trigraphs in C
References
External links
* {{man, bd, iso646.h, SUS, alternative spellings
C (programming language)