5.3 BASIC Character Set
  BASIC uses the full ASCII character set, which includes the
  following:

  .
        The letters A to Z, both upper and lowercase
  .
        The digits 0 to 9
  .
        Special characters

  See the DEC BASIC and VAX BASIC for OpenVMS Systems
  Reference Manual for a complete list of the ASCII character
  set and character values.

  The compiler does not distinguish between upper and low-
  ercase letters, except letters inside quotation marks (called
  string literals ) or letters in a DATA statement. The com-
  piler also does not process characters in a REM statement or
  comment field.

  You can use nonprinting characters in your program-for ex-
  ample, in string literals and constants-but to do so you must
  do one of the following:

  .
        Use a predefined constant such as ESC or DEL
  .
        Use the CHR$ function to specify an ASCII value

  See Section 5.6 for more information about predefined con-
  stants. See Chapter 11 for more information about the CHR$
  function.