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10 <iso646.h> Alternative Operator Spellings

ISO-646 is a character encoding standard that’s very similar to ASCII. But it’s missing a few notable characters, like |, ^, and ~.

Since these are operators or parts of operators in C, this header file defines a number of macros you can use in case those characters aren’t found on your keyboard. (And also C++ can use these same alternate spellings.)

Operator <iso646.h> equivalent
&& and
&= and_eq
& bitand
| bitor
~ compl
! not
!= not_eq
|| or
|= or_eq
^ xor
^= xor_eq

Interestingly, there is no eq for ==, and & and ! are included despite being in ISO-646.

Example usage:

#include <stdio.h>
#include <iso646.h>

int main(void)
{
    int x = 12;
    int y = 30;

    if (x == 12 and y not_eq 40)
        printf("Now we know.\n");
}

I’ve personally never seen this file included, but I’m sure it gets used from time to time.

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