Identifier

A SuperBASIC identifier is a sequence of letters, numbers and underscores.

letter:= | a..z
         | A..Z

number:= | 0..9

identifier:= letter {|letter
                     |number
                     |_       }

example:  a
          limit_1
          current_guess
          counter

An identifier must begin with a letter followed by a sequence of letters, num-
bers and underscores and can be up to 255 characters long. Upper and lower case
characters are equivalent.

Identifiers are used in the SuperBASIC system to identify variables, procedures,
functions, repetition loops etc.

WARNING: NO meaning can be attributed to an identifier other than its ability
         to 'identify' constructs to SuperBASIC. SuperBASIC cannot infer the
         intended use of an identifier from the identifier's name!
