Clearing the screen and other such things.

[Tim McNerney <TIM@MIT-MC.ARPA>]

    Date: Sat, 27 Jul 85 11:38:16 PDT
    From: fateman%ucbdali at Berkeley (Richard Fateman)

    Doesn't UNIX (4.0, 4.1, 4.2 BSD) and those derived from it (e.g. Xenix)
    have a cursor-control package, and aren't there editors (e.g. vi, gnumacs,
    Gosling emacs) that use the termcap (or similar) information files?

Termcap does not address some of the subtleties of many terminals.
For instance: Does the terminal scroll after printing a character in
the last column of the last like?  Also, many terminals support
operations like "Delete N lines," which are almost indispensable for
writing screen editors and the like, are not supported by termcap (nor
KMP's proposal).  Then there is the issue of padding which is not
modeled well at all by termcap.

But, unix aside, because Common Lisp is supposed to be operating
system and machine independent, designing generic I/O in general is
problematic.  Witness the problems that have been raised w.r.t.
interfacing with various files systems (eg. OPEN's :direction :probe).