isalnum - Find whether the given character is alphanumeric or not in C

#include<stdio.h>
#include<ctype.h>

int main()
{
    char a;
    scanf( "%c", &a );
    if( isalnum(a) )
        printf( "This is an alphanumeric character: %c\n", a );
    else
        printf( "This is NOT an alphanumeric character: %c\n", a );
    return 0;
}