You are given a null-terminated string of up to 100 characters. Your task is to:
- Convert all uppercase letters (A–Z) to lowercase (a–z)
- Leave all other characters unchanged (lowercase, digits, symbols, spaces)
- Perform the conversion in-place, using only basic character logic
- Do not use standard functions like tolower()
Example-1
Input: "Hello Embedded"
Output: hello embedded
Example-2
Input: "C99 IS POWERFUL!"
Output: c99 is powerful!
Example-3
Input: "test123"
Output: test123