On Fri, 2007-08-24 at 18:52 -0400, William Case wrote: > 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. That's pretty much it in a nutshell. Generally, RET (ENTER) is used to signify the end of a line. What the program _does_ with that line is up to the program. I was also trying to emphasize that command prompts are really another program (on *nix, the shell; on DOS/Windows, command.com or whatever Windows calls it now) asking for input. ---------------------------------------------------------------------- - Rick Stevens, Principal Engineer rstevens@xxxxxxxxxxxx - - CDN Systems, Internap, Inc. http://www.internap.com - - - - Silence! Or I shall replace you with a very small shell script! - - - The Wizard of OS - ----------------------------------------------------------------------
