ReadKey like Function in C

[Chris Torek]

In article <3727 at buengc.BU.EDU> bph at buengc.BU.EDU (Blair P. Houghton) writes:
>The Compiler writers are in a much better position to implement
>it than are a bunch of fractious C programmers arguing over
>whether to use fstat() or ioctl() and the length of timeout()...

For one thing, this statement is partly false: compiler writers are not
in a position to choose the most appropriate way from {wait up to
.3 seconds for a key, send a signal on key, <any other method>},
and so cannot provide the version most suited to any particular
application.  (Many games, for instance, want `wait for key with
timeout'; many want `wait forever for key'; many want `do not wait for
key'; but still others want something else entirely.)

>Makes me wonder why they haven't, ANSI or no.

Imagine you are the president of IBM or Unisys.  You have $100 billion
worth of customers running systems that treat people like virtual card
punches.  1% of them want ANSI C.  If ANSI C includes a mandatory
ReadKey (whatever it does---all we know for certain at this point is
that it is not compatible with card readers), you will have to commit
many $ to upgrading these systems; if it does not, all you need do
is commit a few $ to writing an ANSI-conformant compiler and runtime
system for these systems.  In return for either effort, you will get
about $1 billion worth of business.

Which do you prefer: to spend about $999+ milllion in return for your
$1 billion (upgrade all those systems, losing the customers who will
not upgrade), or to spend about $1 million in return for your $1 billion
(writing, testing, and supporting compilers for all those systems)?

				-----

Now imagine you are the user on the receiving end of one of these
virtual-card-punch systems.  If ANSI puts a ReadKey function (whatever
it does; all we know is that your system cannot do it) into the
standard, IBM will not bother attempting to earn a few bucks by
upgrading your system and then providing an ANSI C, but if ANSI does
not put a ReadKey function into the standard, IBM will provide a C
compiler.  Which do you prefer: to have no C compiler at all, or
to have one without a standard ReadKey?

				-----

This is, of course, an oversimplification of the issue; but the point
is that this standard is intended to be used in places where ReadKey
cannot be done; therefore this standard cannot say that ReadKey must
be done.  You might prefer a standard that is not so accomodating:
you never touch these systems, for you want a nicer environment than
they could ever provide.  Such standards can and do exist, either
unrelated to, or `sitting above', the language standard.  The POSIX
1003.1 standard, for instance, tells you how to write a nearly
infinite variety of different ReadKey-like functions in C.  All of
them will work on all POSIX 1003.1-conformant systems.
-- 
In-Real-Life: Chris Torek, Univ of MD Comp Sci Dept (+1 301 454 7163)
Domain:	chris at mimsy.umd.edu	Path:	uunet!mimsy!chris