Path: utzoo!utgpu!attcan!uunet!husc6!rutgers!mailrus!iuvax!bsu-cs!dhesi
From: dhesi@bsu-cs.UUCP (Rahul Dhesi)
Newsgroups: comp.sys.ibm.pc
Subject: Re: Microsoft C Bug or Feature ?????
Summary: bug in MS-DOS
Message-ID: <3559@bsu-cs.UUCP>
Date: 4 Aug 88 15:32:29 GMT
References: <8808021504.AA05128@wilson.csri.toronto.edu>
Reply-To: dhesi@bsu-cs.UUCP (Rahul Dhesi)
Organization: CS Dept, Ball St U, Muncie, Indiana
Lines: 30

In article <8808021504.AA05128@wilson.csri.toronto.edu> byu@csri.toronto.edu
(Benjamin Yu) writes:
>I was trying to putc a byte (hex 1A) to stdprn using Microsoft C V4.0.
>Since hex 1A is ctrl-Z which stands for end-of-file, the byte is never
>sent.

This is really a bug in MS-DOS, though it was probably intended as a
feature.

When sending output to a character-oriented device, a control Z is used
to indicate end-of-file too.  This isn't necessary, but it happens.  So
the PRN printer device driver, when it sees control-Z, assumes no more
data will arrive and freezes up, refusing to accept any more
characters.

To see this philosphy in action, try giving MS-DOS this command:

    echo ^Z

If all goes normally, you will see the response "Insufficient disk space".
What really happened was that when the console driver saw the control
Z, it assumed end-of-file had arrived, and so refused to accept any
data.  COMMAND.COM realized that the console was refusing to print, and
assumed that it couldn't send stuff because of a full disk.

A hypothetical solution is to put the printer device into raw mode.
You have to write a program to do this.  I don't know if it will work
for you.
-- 
Rahul Dhesi         UUCP:  <backbones>!{iuvax,pur-ee,uunet}!bsu-cs!dhesi