C alternative tokens

C Standard Library
Data types Character classification Strings Mathematics File input/output Date/time Localization Memory allocation Process control Signals Alternative tokens Miscellaneous headers: <assert.h> <errno.h> <setjmp.h> <stdarg.h>

C alternative tokens refer to a set of alternative spellings of common operators in the C programming language. They are implemented as a group of macro constants in the C standard library in the iso646.h header. The tokens were added to the standard in a 1995 amendment to the C90 standard.

The alternative tokens allow programmers to use C language bitwise and logical operators which could otherwise be hard to type on some international and non-QWERTY keyboards. The name of the header file they are implemented in refers to the ISO646 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:

Macro	Defined as
and	&&
and_eq	&=
bitand	&
bitor	|
compl	~
not	!
not_eq	!=
or	||
or_eq	|=
xor	^
xor_eq	^=

C++

The abovementioned 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 standard provides the header <ciso646>. However the latter file has no effect, being empty. Notwithstanding some compilers, such as Microsoft Visual C++, do require the header to be included in order to use these identifiers.

See also

• Digraphs and trigraphs in C

External links

• iso646.h: alternative spellings – Base Definitions Reference, The Single UNIX® Specification, Issue 7 from The Open Group