OT What does RET (Enter) do and how does it do it ??

[William Case]

Thanks Rick;

I put your answer together with Alan's and I think I get a satisfying
answer.

On Fri, 2007-08-24 at 15:09 -0700, Rick Stevens wrote:
> On Fri, 2007-08-24 at 17:42 -0400, William Case wrote:
> > Hi;
> > 
> > This question is meant as a Friday afternoon to a Sunday evening
> > discussion. It is not rush; but I have been unable to discover an answer
> > to what seems to me a basic question on how my computer works.
> > 
> > 
> 
[snip]

> Well, it's simple.  The intent of text editors, word processors and the
> like is that whatever you type in gets saved in the file.  In *nix-ish
> operating systems (Linux, Unix, MacOS, etc.), the RETURN or ENTER key is
> denoted by a single character in the file.  We call this the "newline"
> character, which is the hexadecimal value 0x0a.  In ASCII parlance,
> that's the "LF" or "linefeed" character.  The LF character can also
> be entered by holding down the "CTRL" key and pressing "j" (also
> sometimes called "control-J").
> 
> In Windows-type stuff (DOS, Windows, CP/M, etc.), the ENTER key is
> denoted by a two character sequence, the hex value 0x0d (ASCII "CR" or
> "carriage return"), followed by the hex value 0x0a (ASCII "LF" or
> "linefeed" again).  We call this sequence the "CRLF" sequence.  Note
> that the "CR" character can also be entered by holding down the "CTRL"
> key and pressing "m", which is why it's sometimes called "control-M".
> 
> (ADDITIONAL INFO: The hex value of "m" is "0x4d" and that of "j" is
> 0x4a.  Holding down the CTRL key inhibits the generation of bit 6 or
> the value of 0x40, so CTRL-M generates 0x0d instead of 0x4d.  Easy.)
> 
> So much for text editors, word processors and the like.  Now, when
> you're at a command prompt or other program requesting input (remember
> that the command prompt is the shell program asking for input), the
> RETURN (or ENTER) key signals the end of user input and the program then
> processes that according to whatever the program is supposed to do.
> 
> Does that clarify things?
> 
To re-summarize, the meaning of RET is established by the program being
used.  The program can create it's own meaning for RET; or use a
standardized meaning according to what has been bound to the keymap the
program is using, or redefine the keymap it uses to bind one or another
meaning to a key press or event.

-- 
Regards Bill