Path: utzoo!attcan!uunet!lll-winken!lll-tis!ames!ucsd!ucsdhub!hp-sdd!ncr-sd!ncrlnk!ncrcce!mercer
From: mercer@ncrcce.StPaul.NCR.COM (Dan Mercer)
Newsgroups: comp.lang.c
Subject: Re: Getchar w/wout echo
Summary: Don't confuse language functions with os functions
Message-ID: <731@ncrcce.StPaul.NCR.COM>
Date: 29 Aug 88 21:44:42 GMT
References: <371@marob.MASA.COM> <65071@sun.uucp> <624@proxftl.UUCP>
Reply-To: mercer@ncrcce.StPaul.NCR.COM (Dan Mercer)
Organization: NCR Comten, Inc.
Lines: 30


	Another one of those fine confused wish list discussions.  Unfortunately,
	like the other discussions of this type,  it is fatally flawed.	
	The problem is,   evreyone seems to be confusing language functionality
	with os functionality.  Terminal echo is a function provided by the
	operating system (in this case,  UNIX(tm)).  Whether or not echoing
	is going on is invisible to getchar(),  and read.  The tty device driver
	is controlling this operation,  and only an ioctl can change its
	behaviour.  In many cases,  the echoing function is not even taking
	place on the same processor.  In the NCR TOWER(tm) series,  the
	echoing is being done on the HPSIO (a separate 68010 based processor)
	and is thereby not burdening the CPU. 

	In Amdahl hosts running UTS in a network,  the echoing may be
	done by and Amdahl 4705(tm) channel attached to the host.
	Ioctl calls will generate commnds to the front end processor to
	change its character reading behaviour.

	In fact,  in many cases,  the echo may already have occurred
	before the echoing can be turned off.

	Before you go mucking with the language,  I suggest you learn
	a bit more about your hardware,  your operating system,  and
	how they interrelate.  Then I suggest you do what I did when I
	wrote a menuing system - read everything available about the
	tty device drivers,  stty,  and termio,  experiment like
	crazy,  then write your own raw character input routines.

	No flame intended.

	Dan Mercer - NCR COMTEN