DEFtype - BASIC declarations that set the default data type
          for variables, DEF FN functions, and FUNCTION procedures
 
Syntax
  DEFINT letterrange [,letterrange]...
  DEFSNG letterrange [,letterrange]...
  DEFDBL letterrange [,letterrange]...
  DEFLNG letterrange [,letterrange]...
  DEFSTR letterrange [,letterrange]...
 
    - letterrange has the form
        letter1[-letter2]
      where letter1 and letter2 are any of the upper or lowercase letters
      of the alphabet. Variable and function names beginning with the letters
      in letterrange have the type specified by the last three letters of
      the keyword (INT, SNG, DBL, LNG, or STR).