Identifiers 标识符

1. What is an Identifier?

An identifier is a name given to programming elements like variables, functions, arrays, structures, etc. It's how we reference these elements in our code.

2. Identifier Rules and Syntax

1. First character: letter or underscore
2. Subsequent chars: letters, digits, underscores
3. Case sensitive: 'age' ≠ 'Age' ≠ 'AGE'
4. Length: At least first 31 chars are significant
5. Cannot use C keywords: int, if, for, etc.