C library function - isalnum()


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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 non-zero value if c is a digit or a letter, else it returns 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, to produce the following result −

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

ctype_h.htm

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