11.1.2.1 ASCII Function
  The ASCII function returns the numeric ASCII value of a
  string's first character. The ASCII function returns an in-
  teger value from 0 to 255, inclusive. For instance, in the
  following example, the PRINT statement prints the inte-
  ger value 66 because this is the ASCII value equivalent of an
  uppercase B, the first character in the string:
  test_string$ = "BAT"
  PRINT ASCII(test_string$)
  END

  Output
    66
  Note that the ASCII value of a null string is zero.