Header File 

ctype.h, wctype.h 

Category 

Classification Routines 

Prototype 

int isxdigit(int c); 

int iswxdigit(wint_t c); 

Description 

Tests for hexadecimal character. 

isxdigit is a macro that classifies ASCII-coded integer values by table lookup. The macro is affected by the current locale’s LC_CTYPE category. 

You can make this macro available as a function by undefining (#undef) it. 

Return Value 

isxdigit returns nonzero if c is a hexadecimal digit (0 to 9, A to F, a to f) or any other hexadecimal digit defined by the locale. 

Example  

#include <stdio.h>
#include <ctype.h>
int main(void)
{
  char c = 'C';
  if (isxdigit(c))
    printf("%c is a hexadecimal digit\n",c);
  else 
    printf("%c is not a hexadecimal digit\n",c);
  return 0;
}

Portability