C library function - isalnum()

Description

The C library function void isalnum(int c) checks if the passed character is alphanumeric.

Declaration

Following is the declaration for isalnum() function.

int isalnum(int c);

Parameters

• c -- This is the character to be checked.

Return Value

This function returns nonzero value if c is a digit or a letter, else 0

Example

The following example shows the usage of isalnum() function.

#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);
}

Let us compile and run the above program, this will produce the following result:

var1 = |d| is alphanumeric
var2 = |2| is alphanumeric
var3 = | | is not alphanumeric
var4 = | | is not alphanumeric