Clearing the screen and other such things.

[Rob MacLachlan <RAM@CMU-CS-C.ARPA>]

    Perhaps this "virtual terminal" package would be best put into the
    yellow pages.  Given a sufficiently efficient implementation of the
    basic terminal I/O stream or at least a binary stream to the terminal,
    it could be written entirely in Lisp.

This is only true given that there is a physical terminal which can be
controlled by sequences of characters  ---  a totally unwarranted
assumption. 

 From an earlier message:

       ERASE-CHAR-BACKWARD, ERASE-CHAR-FORWARD

    Many terminals don't support these operations.  If we are trying to
    limit ourselves to a set of essential primitives, I would suggest that
    these be flushed, since they are merely abstractions for printing the
    sequences, backspace-space-backspace and space-backspace,
    respectively.

This argument is not valid, since there is no reason to suppose that
"printing" these characters on the "terminal" will have the desired
effect.  A Common Lisp implementation doesn't even have to have a
backspace character.

  Rob