C: How can I convert uppercase to lowercase and reverse without using any standard function or method?

Answer 1

1) Go through the entire string character by character and check the ascii value of the char.
2) If the ascii value falls in the upper case range, then make it lower case by adding 32
3) If the ascii value falls in the lower case range, then make it upper case by subtracting 32

The upper case letters are in the range 'A' to 'Z' 65 to 90
The lower case letters are in the range 'a' to 'z' 97 to 122 (see ascii tables)