Follow these rules when naming variables:
- A variable name must be of the form $name or ${name}.
- The string name can consist of letters (a-z and A-Z), numbers (0-9), and underscore characters (_).
- The first character of name must be an alphabetic character (a-z or A-Z).
- If the ${name} form is used, spaces can also appear in name. This allows you to use multiple word names without the underscore character.
- C language is case sensitive so best practice is have lower case of variable names.
- Reserved names can’t be variables.