C语言isalnum()库函数

// C语言库isalnum()函数
#include <stdio.h>
#include <ctype.h>

int main () {
   int var1 = 'd';
   int var2 = '2';
   int var3 = '	';
   int var4 = ' ';

   if( isalnum(var1) ) {
      printf("var1 = |%c| is alphanumeric/n", var1 );
   } else {
      printf("var1 = |%c| is not alphanumeric/n", var1 );
   }

   if( isalnum(var2) ) {
      printf("var2 = |%c| is alphanumeric/n", var2 );
   } else {
      printf("var2 = |%c| is not alphanumeric/n", var2 );
   }

   if( isalnum(var3) ) {
      printf("var3 = |%c| is alphanumeric/n", var3 );
   } else {
      printf("var3 = |%c| is not alphanumeric/n", var3 );
   }

   if( isalnum(var4) ) {
      printf("var4 = |%c| is alphanumeric/n", var4 );
   } else {
      printf("var4 = |%c| is not alphanumeric/n", var4 );
   }
   return(0);
}