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Path: utzoo!dciem!nrcaer!cognos!brianc
From: brianc@cognos.UUCP (Brian Campbell)
Newsgroups: comp.sys.ibm.pc
Subject: Re: DOS line editing
Message-ID: <324@cognos.UUCP>
Date: Fri, 23-Jan-87 10:00:11 EST
Article-I.D.: cognos.324
Posted: Fri Jan 23 10:00:11 1987
Date-Received: Sat, 24-Jan-87 09:56:07 EST
References: <307@cognos.UUCP> <321@rocky2.UUCP>
Reply-To: brianc@cognos.UUCP (Brian Campbell)
Organization: Cognos Inc., Ottawa, Canada
Lines: 48
Summary: 

In article <321@rocky2.UUCP> reintom@rocky2.UUCP (Tom Reingold) writes:
>
>In article <307@cognos.UUCP>, brianc@cognos.UUCP (Brian Campbell) writes:
>> 
>>      In almost every version I used up to and including 3.1, there has
>> been a Ctrl-U and Ctrl-W keystroke which is recognized.  [For those of
>> you who didn't know of or didn't have these features, Ctrl-U erases the
>> entire line (similar to ESC, but on the same line) and Ctrl-W erases
>> backward to the last non-alphanumeric character]. 
>> 
>> 
>I formatted our hard disk at work and noticed the same thing as you.  It is
>not the version of DOS that is in question.  It is really a bug in the
>format program because it happens only on some hard disks.  I was using
>the original IBM floppy disk that had no write-enable notch.  There were
>two differences between the system files on the floppy and the hard disk.
>I patched the one on the hard disk to be the same as on the floppy and
>the editing keys returned.
>
>These editing features were not documented and have been removed from DOS
>3.2  It seemed like a shame to me but I recently got a copy of CED, a
>freeware command editor.  Having it is far better than having Ctrl-U and
>Ctrl-W.  It gives command history and much more.  I suggest you get a copy.
>It's really good.  You won't miss the editing keys.
>
>-Tom

Ridiculous!!!

Not only are the editing features available in DOS 3.20 (patch below), but
I find it *extremely* hard to believe that the format program could just
occasionally replace four different non-consecutive bytes of one of the system
files with NOP's (which is what the difference between having Ctrl-U & Ctrl-W
and not amounts to).

The following code fragment is identical in both DOS 3.10 and DOS 3.20 -- it
is located at offset (using DEBUG) 1DB9 in former and 1E96 in the latter.

   3C 17	CMP	AL,17
   74 5E	JZ	$+60
   3C 15	CMP 	AL,15
   74 51	JZ	$+53

All that is really necessary here are the two JZ instructions.  In some
versions of DOS it seems they were left out (but the CMP's are still done!)

Brian Campbell