isascii() - test for ASCII character
#include <ctype.h>
int isascii (int c)
The isascii(3) function tests for an ASCII character, which is any character with a value less than or equal to 0177.
isalnum(3)
isalpha(3)
isblank(3)
iscntrl(3)
isdigit(3)
isgraph(3)
islower(3)
isprint(3)
ispunct(3)
isspace(3)
isupper(3)
isxdigit(3)
tolower(3)
toupper(3)