Is Alnum

#include "stdio.h"
char alnum(int x)

{
     if(x>='a'&& x<='z'|| x>='A'&& x<='Z'||x>='0'&& x<='9')
     return (1);
     else
     return (0);
}
int main (void)
{
    char  a;       
    printf("Enter a alphabet or number:\n");
    scanf("%c",&a );
    printf("%d\n",alnum(a));
    system("pause");
    return 0;
}