Path: utzoo!attcan!uunet!lll-winken!ames!ncar!tank!mimsy!chris
From: chris@mimsy.UUCP (Chris Torek)
Newsgroups: comp.lang.c
Subject: inkey$, noecho, and other impossibles
Message-ID: <15396@mimsy.UUCP>
Date: 11 Jan 89 04:42:51 GMT
References: <19@xenlink.UUCP> <225800106@uxe.cso.uiuc.edu> <310@twwells.uucp> <84629@sun.uucp>
Organization: U of Maryland, Dept. of Computer Science, Coll. Pk., MD 20742
Lines: 42

->In article <225800106@uxe.cso.uiuc.edu> mcdonald@uxe.cso.uiuc.edu writes:
->>some such function [like inkey() or kbhit()] should be a
->>STANDARD C (ANSI C) function ....

-In article <310@twwells.uucp> bill@twwells.UUCP (T. William Wells) writes:
->And to repeat what has been said by many: IT CAN'T BE DONE!
[in some cases where the rest of the dpANS *can*]

In article <84629@sun.uucp> swilson%thetone@Sun.COM (Scott Wilson) writes:
-This argument is very similar to one I started some time ago related
-to echo/no echo on input, etc.  The point of standard libraries is
-to smooth over OS dependencies to provide a uniform interface.  If
-inkey() cannot be provided for on some systems, aren't there other
-operations mandated by the Standard that are just as hard to provide?

No.

-For example, what about the legal modes passed to fopen()?  Aren't
-there some systems where you simply can't open a file for simultaneous
-reading and writing?  Or open for writing at the end of a file?  What
-about fseek(), couldn't that be potentially very inefficient to
-implement on some brain-damaged systems?

There are a number of systems on which stdio might be fairly slow.  As
far as I know, however, there are *no* systems (other than standalones)
in which it cannot be done at all.  But since C runs on IBM machines
that see only input screens (collected by 3270s) and on systems with
half-duplex ASR 33s, it is easy to see that both get-one-character-
without getting-a-line and turn-off-echo are indeed sometimes impossible.

-... I guess what I'm wondering is:  are there operations
-already part of the Standard that are there for historical reasons
-(i.e., it has always existed for most implementations) that would be
-rejected if it was recommended as a new feature because it was "too
-operating system dependent?"

Possibly.  In fact, malloc() might be one (`too machine dependent').
But most things in the standard can be done everywhere, even on those
old IBM systems.
-- 
In-Real-Life: Chris Torek, Univ of MD Comp Sci Dept (+1 301 454 7163)
Domain:	chris@mimsy.umd.edu	Path:	uunet!mimsy!chris