tolower() function in C

• Difficulty Level : Easy
• Last Updated : 01 Oct, 2018

The tolower() function is defined in the ctype.h header file. If the character passed is a uppercase alphabet then the tolower() function converts a uppercase alphabet to an lowercase alphabet.

Syntax:

int tolower(int ch);

Parameter: This method takes a mandatory parameter ch which is the character to be converted to lowercase.

Return Value: This function returns the lowercase character corresponding to the ch.

Below programs illustrate the tolower() function in C:

Example 1:-

// C program to demonstrate

// example of tolower() function.

#include <ctype.h>

#include <stdio.h>

int main()

{

    // Character to be converted to lowercase

    char ch = 'G';

    // convert ch to lowercase using toLower()

    printf("%c in lowercase is represented as = %c", ch, tolower(ch));

    return 0;

}

Output:

G in lowercase is represented as = g

Example 2:-

// C program to demonstrate

// example of tolower() function.

#include <ctype.h>

#include <stdio.h>

int main()

{

    int j = 0;

    char str[] = "GEEKSFORGEEKS\n";

    // Character to be converted to lowercase

    char ch = 'G';

    // convert ch to lowercase using toLower()

    char ch;

    while (str[j]) {

        ch = str[j];

        // convert ch to lowercase using toLower()

        putchar(tolower(ch));

        j++;

    }

    return 0;

}

Output:

geeksforgeeks