isblank() - white-space character test
#include <ctype.h>
int isblank (int c)
The isblank(3) function tests whether c is a character of the class blank in the program's current locale. For the C and POSIX locales, this is the characters space and horizontal tab.
The isblank(3) function returns non-zero if the character is a blank character and returns zero if the character is not.
isalnum(3)
isalpha(3)
iscntrl(3)
isdigit(3)
isgraph(3)
islower(3)
isprint(3)
ispunct(3)
isspace(3)
isupper(3)
isxdigit(3)
tolower(3)
toupper(3)