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tolower() Function in C

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tolower() function in C is used to convert the uppercase alphabet to the lowercase alphabet. It does not affect characters other than uppercase characters. It is defined in the <ctype.h> header file in C.

Syntax

The syntax of tolower() function is:

int tolower(int c);

Parameter

  • This function takes a character as a parameter.

Return Value

  • It returns the ASCII value corresponding to the lowercase of the character passed as the argument.

Examples of tolower() Function

Example 1

The below C program demonstrates the tolower() function.

C

// C program to demonstrate
// example of tolower() function.
#include <ctype.h>
#include <stdio.h>
 
int main()
{
 
    // convert 'M' to lowercase
    char ch = tolower('M');
 
    // Printing the lowercase letter
    printf("%c", ch);
 
    return 0;
}

                    

Output
m

Example 2

The below code converts all uppercase letters in the string to their lowercase equivalents, while leaving other characters unchanged.

C

// C program to demonstrate
// example of tolower() function.
#include <ctype.h>
#include <stdio.h>
 
int main()
{
 
    char s[] = "Code_in_C_@0123";
 
    // This will just convert
    // uppercase letters in string
    // to lowercase. Other characters
    // will remain unaffected.
    for (int i = 0; i < strlen(s); i++) {
        s[i] = tolower(s[i]);
    }
 
    // Printing the output
    printf("%s", s);
 
    return 0;
}

                    

Output
code_in_c_@0123


Last Updated : 06 Jun, 2023
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