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ISASCII(3) Library Functions Manual ISASCII(3)

ASCII character test

#include <ctype.h>
isascii(int c);

The isascii() function tests for an ASCII character, which is any character with a value less than or equal to 0177.

The isascii() function returns zero if the character tests false or non-zero if the character tests true.

isalnum(3), isalpha(3), isblank(3), iscntrl(3), isdigit(3), isgraph(3), islower(3), isprint(3), ispunct(3), isspace(3), isupper(3), isxdigit(3), stdio(3), toascii(3), tolower(3), toupper(3), ascii(7)

The isascii() function conforms to X/Open Portability Guide Issue 4 (“XPG4”).

The isascii() function first appeared in Version 7 AT&T UNIX.

The argument to isascii() must be EOF or representable as an unsigned char; otherwise, the result is undefined.
July 17, 2013 OpenBSD-current