Thanks again Alan; On Sat, 2007-08-25 at 00:36 +0100, Alan Cox wrote: > > programs like emacs. But you are saying that this equally applicable to > > all programs. That I could, if I wanted change the function of RET by > > changing the keymap a particular application uses. It is just that the > > use of RET is fairly well standardized. > > Its partly wired in. Certain parts of the behaviour are encoded into the > terminal layer in the kernel (originally designed from the days people > sat at terminals with serial links (or current loop) to the box in the > data centre. > > In normal line by line behaviour the return key is fixed (you can pick > between carriage-return and line feed that is all), but the other > 'special' characters like the delete key can be changed. This is so > called "canonical" or "cooked mode". You can turn this off to do character > by character processing (as emacs does) which is "raw mode". > > The idea of cooked mode is that most programs at the time wanted lines of > typed input so the kernel handles this to ensure the editing behaviour was > standard, it was efficient and on big machines (with hundreds of > terminals) you didn't wake processes each keypress. Indeed some machines > had serial ports that didn't wake the machine but supported all the line > editing features in hardware until you hit return. A year or so ago when I was reading about keyboard input and tty, I came across canonical mode, and couldn't figure out what it would be used for, shrugged (kinda), assumed it was only of historical interest and moved on. I will re-visit canonical mode and see how it applies. -- Regards Bill
