C Program to Convert Character to Lowercase

In this article we will show you, How to convert the given character to lowercase using tolower built-in function and also by not using tolower function.

tolower Function

In C Programming, tolower is a built-in function present in the header file which is used to convert the character to uppercase. The Syntax of the tolower function is

tolower (<Character>);

C Program to Convert Character to Lowercase using tolower function

This C program allows the user to enter any character and convert the character to lowercase using the built-in ctype function called tolower.

#include <stdio.h>  
#include <ctype.h> 

int main()
{
  char Ch;

  printf("\n Please Enter any alphabet\n");
  scanf(" %c", &Ch);
  
  if (isalpha(Ch) )
   {  
     Ch = tolower(Ch); 
     printf ("\n Lowercase of Entered character is %c", Ch);
   }
  else
   {
     printf("\n Please Enter Valid Alphabet");
   }  
}

OUTPUT

ANALYSIS
In this program we declared a character variable Ch. Below printf statement will asked to enter any character you like.

 printf("\n Please Enter any alphabet\n");

scanf(" %c", &Ch);

In the next line we used the If Statement,

if (isalpha(Ch) )

If the above condition is TRUE then the given character is an Alphabet and now we can convert the given character to Lowercase using below statement

Ch = tolower(Ch);

In the next line we have the printf statement to print the converted Lowercase letter

printf ("\n Lowercase of Entered character is %c", Ch);

printf("\n Please Enter Valid Alphabet");

C Program to Convert Character to lowercase without using tolower function

This C program allows the user to enter any character and convert the character to lowercase without using built-in ctype function tolower.

In this example, We are going to use the ASCII code to convert uppercase character to lowercase. Please refer ASCII Value of a Character article to understand the ASCII values of every character.

#include <stdio.h>  

int main()
{
  char Ch;
 
  printf("\n Please Enter any alphabet\n");
  scanf(" %c", &Ch);

  if (isalpha(Ch) )
  {
    if (Ch>=65 && Ch<=90)
     {  
       Ch = Ch + 32; 
       printf ("\n Lowercase of Entered character is %c", Ch);
     }
    else
     {
       printf("\n You Already Entered Lowercase Character");
     }  
   }
  else
   {
     printf("\n Entered character is Not an Alphabet");
   }  
}

OUTPUT

Let us see what happens when we enter Lowercase letter as Ch

Now, Let us see what happens when we enter Digit as Ch

ANALYSIS
If you look at the Nested If Statement

if (Ch>=65 && Ch<=90)

//or We can Simply Say
if (Ch >= 'A' && Ch <= 'Z')

As we all know that, all the uppercase characters are between A and Z and their ASCII codes are 65 to 90. So, the above if condition will check whether the given character is between A and Z.

If the above condition is TRUE then we have to convert the given character to lowercase. If you observe the ASCII codes of uppercase and lowercase characters, the difference between them is 32. For instance ASCII code for a = 97 & A = 65 (Difference is 32) that’s why we adding 32 to the character ASCII value.

Ch = Ch + 32;

In the next line we have the printf statement to print the converted Lowercase letter

printf ("\n Lowercase of Entered character is %c", Ch);

If the above condition is FALSE then the given character is already in lowercase So, it will print below statement

printf("\n You Already Entered Lowercase Character");

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