What are the rules for defining character constants in the C language?

The rules for defining character constants in the C language are as follows:

1. Character constants are enclosed in single quotes.
2. Only one character is allowed. For example: ‘a’.
3. Special characters can be represented using escape sequences, for example: ‘\n’ represents a newline character.
4. Character constants can be any character, including letters, numbers, special characters, etc.
5. Character constants are stored in memory in the form of ASCII codes, taking up 1 byte of space.