| C Standard Library |
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The iso646.h header file is part of the C standard library. It was added to this library in a 1995 amendment to the C90 standard. It defines a number of macros which allow programmers to use C language bitwise and logical operators, which, without the header file, cannot be quickly or easily typed on some international and non-QWERTY keyboards.
The filename 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.
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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 | ^= |
These 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.[1]