Letter Case Conversion
Letter case conversion refers to changing the case of characters in a string, such as converting uppercase letters to lowercase or vice versa. This is useful when you need to standardize text input, perform comparisons, or format data in a specific way.

Here are the most common types of letter case conversions:

Uppercase to Lowercase
Lowercase to Uppercase
Toggle Case (Uppercase letters become lowercase and vice versa)
Title Case (First letter of each word is capitalized)
Common Case Conversion Operations:
1. Uppercase to Lowercase
Converts all uppercase letters in a string to lowercase.

Example:

Input: "HELLO WORLD"
Output: "hello world"
2. Lowercase to Uppercase
Converts all lowercase letters in a string to uppercase.

Example:

Input: "hello world"
Output: "HELLO WORLD"
3. Toggle Case
Converts uppercase letters to lowercase and vice versa.

Example:

Input: "Hello World"
Output: "hELLO wORLD"
4. Title Case
Capitalizes the first letter of each word in a string, while leaving other letters in lowercase.

Example:

Input: "hello world"
Output: "Hello World"