Variable Names
 
A BASIC variable name may contain up to 40 characters. The characters
allowed in a variable name are letters, numbers, the period (.), and
the type-declaration characters (%, &, !, #, and $). The first character
in a variable name must be a letter. If a variable begins with FN, it is
assumed to be a call to a DEF FN function.
 
A variable name cannot be a reserved word, but embedded reserved words are
allowed. For example, the following statement is illegal because LOG is a
reserved word (BASIC is not case sensitive):
 
  Log = 8
 
However, the following statement is legal:
 
  TimeLog = 8
 
Reserved words include all BASIC commands, statements, function names, and
operator names.
 
Note: Variable names cannot duplicate procedure (SUB and FUNCTION) names
      or symbolic constant (CONST) names.