C库函数 isalnum()

#include <stdio.h>

#include <ctype.h>



int main () {

   int var1 = 'd';

   int var2 = '2';

   int var3 = '\t';

   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);

}