tolower() Function in C

C tolower() function is part of the C standard Library used to convert the uppercase alphabet to the lowercase alphabet. It does not affect characters other than uppercase characters.

Example

a

Syntax of tolower()

The tolower() function is defined in the <ctype.h> header file.

where,

• c: character that is to be converted. It is generally passed as integer that can represent an unsigned char.

Return Value

• If the passed character is an uppercase character then it returns the ASCII value corresponding to the lowercase of the character passed as the argument.
• If the passed character is already a lowercase or not a letter then it returns the same character.

Examples of tolower() Functions

The below examples demonstrate how to use the tolower() function in C:

Example 1

The below C program demonstrates the tolower() function.

Original Character: M
After using tolower: m

Example 2

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