An open-ended means of classifying characters. : Wide Character Functions « Wide Character String « C Tutorial

1. C Tutorial
2. Wide Character String
3. Wide Character Functions

1. alnum
2. digit
3. print
4. upper
5. alpha
6. graph
7. punct
8. xdigit
9. cntrl
10. lower
11. space

The following fragment demonstrates the wctype() and iswctype() functions:

#include <wctype.h>
#include <stdio.h>

int main(void){

  wctype_t x;

  x = wctype("space");

  if(iswctype(L' ', x)){
    printf("Is a space.\n");
  }

}

(C: The Complete Reference, Fourth Edition by Herbert Schildt McGraw-Hill/Osborne 2000 ISBN-10: 0072121246, ISBN-13: 978-0072121247)