Date: Sun, 14 May 2000 11:03:02 +0930 From: Greg Lehey <grog@lemis.com> To: gh <grasshacker@linkfast.net> Cc: FreeBSD Questions <questions@FreeBSD.org> Subject: Re: DEL key acts like BackSpace Message-ID: <20000514110301.H847@freebie.lemis.com> In-Reply-To: <035c01bfbc9f$582bca30$b864aad0@kickme> References: <20000512233212.A443@casimirhost.kasby> <20000513114953.I31094@freebie.lemis.com> <035c01bfbc9f$582bca30$b864aad0@kickme>
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On Saturday, 13 May 2000 at 0:51:54 -0500, gh wrote:
>
>
>> On Friday, 12 May 2000 at 23:32:12 +0200, Francesco Casadei wrote:
>>> Why the DEL key deletes the character before the cursor (just like
>>> BackSpace) instead of deleting the character after the cursor?
>>
>> Because that's its purpose.
>>
>>> Only in Netscape Navigator's location bar DEL deletes the characters
>>> to the right of the cursor.
>>
>> I consider this incorrect.
>
> Would you mind pointing me toward some explanation of why that behavior is
> considered incorrect?
> To me, it seems logical.
>
> Backspace -> back...space.
> Delete -> why have another backspace?
Delete was there first, on the ASR33/35. Backspace didn't make it
until the mid-70s. And, indeed, we said "why have another
backspace?".
> Is there some historical explanation? Is it just a "geeky-hacker"
> thing?
Well, there are a few things:
1. As mentioned, the original Teletypes used in just about all
machines of the late 60s/early 70s had a DEL button but no
BS/Backspace button. All the software I know of used DEL to
delete the previous character. It had the additional advantage of
being able to overwrite the character after it had been punched on
tape: DEL is all bits set, and the paper tape reader just ignored
this particular sequence.
At this time, of course, there was no concept of a cursor or a
following character, so we only needed one character.
2. After video terminals arrived, nothing much changed. Most editors
and command line editing schemes were the same as before.
Gradually, though, people started using ctrl-H as the erase
character, because that's what ANSI decreed. The result was what
we have today: two characters for the same function.
3. Independently, real full-screen text editors started to appear.
vi decided that control characters were Evil, so it used normal
characters. Emacs decided that modes were Evil, so it used all
control characters for some purpose. It decided on ctrl-d for the
delete forward key. It also decided on DEL for the delete
backward key and ctrl-h for the Help key, a problem that we still
have today.
Later, shells appeared with command line editing. With the
exception of csh's remarkably primitive editing, they all followed
either vi or Emacs.
4. Meanwhile, in Washington State, a company reinvented everything
and used completely different characters from what other people
were using. That's their choice, of course, but it doesn't mean
anybody else is going to follow them, especially when most of
their choices appear to be suboptimal.
Greg
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