Identifiers can contain spaces.
There are some rules for naming correctly of your identifier, you have to follow for naming identifiers: The first character of the identifier must be a letter of the alphabet (upper or lowercase) or an underscore ('_'). The rest of the identifier name can consist of letters (upper or lowercase), underscores ('_') or digits (0-9). It should start with a letter or with an underscore symbol ( _) but not with a digit. ... Thus, float or double, and int are invalid identifiers. Example: 1abc is the incorrect syntax of the identifier.