C library functions -isalnum()

C Standard Library - <ctype.h>

Description

C Library Functionsvoid isalnum(int c)Check whether the passed character is alphanumeric.

Declaration

Below is the declaration of the isalnum() function.

int isalnum(int c);

Parameter

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

Return Value

If c is a digit or a letter, the function returns a nonzero value; otherwise, it returns 0.

Example

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

Example

#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| 是字母数字
var2 = |2| 是字母数字
var3 = | | 不是字母数字
var4 = | | 不是字母数字

C Standard Library - <ctype.h>

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