<http://lists.suckless.org/dev/1404/20697.html>:
Well, I am going to comment why I want to change the behaviour
- of this key. When ascii was defined in 1968 communication
- with computers were done using punched cards, or hardcopy
- terminals (basically a typewritter machine connected with
- the computer using a serial port). Due to this, ascii defines
- DELETE as 7F, because in the puched cards, it means all the
- holes of the card punched, so it is a kind of 'phisical
- delete'. In the same way, BACKSPACE key was a non destructive
- back space, as in typewriter machines. So, if you wanted
- to delete a character, you had to BACKSPACE and then DELETE.
- Other use of BACKSPACE was accented characters, for example
- 'a BACKSPACE `'. The VT100 had no BACKSPACE key, it was
- generated using the CONTROL key as another control character
- (CONTROL key sets to 0 b7 b6 b5, so it converts H (code
- 0x48) into BACKSPACE (code 0x08)), but it had a DELETE key
- in a similar position where BACKSPACE key is located today
- in common PC keyboards. All the terminal emulators emulated
- correctly the difference between these keys, and backspace
- key generated a BACKSPACE (^H) and delete key generated a
- DELETE (^?).
-
- But the problem arised when Linus Torvald wrote Linux, and
- he did that the virtual terminal (the terminal emulator
- integrated in the kernel) returns a DELETE when backspace
- was pressed, due to the fact of the key in that position
- in VT100 was a delete key. This created a lot of problems
- (you can see it in [1] and [2]), and how Linux became the
- king, a lot of terminal emulators today generate a DELETE
- when backspace key is pressed in order to avoid problems
- with linux. It causes that the only way of generating a
- BACKSPACE in these systems is using CONTROL + H. I also
- think that emacs had an important point here because CONTROL
- + H prefix is used in emacs in some commands (help commands).
+ of this key. When ASCII was defined in 1968, communication
+ with computers was done using punched cards, or hardcopy
+ terminals (basically a typewriter machine connected with the
+ computer using a serial port). ASCII defines DELETE as 7F,
+ because, in punched-card terms, it means all the holes of the
+ card punched; it is thus a kind of 'physical delete'. In the
+ same way, the BACKSPACE key was a non-destructive backspace,
+ as on a typewriter. So, if you wanted to delete a character,
+ you had to BACKSPACE and then DELETE. Another use of BACKSPACE
+ was to type accented characters, for example 'a BACKSPACE `'.
+ The VT100 had no BACKSPACE key; it was generated using the
+ CONTROL key as another control character (CONTROL key sets to
+ 0 b7 b6 b5, so it converts H (code 0x48) into BACKSPACE (code
+ 0x08)), but it had a DELETE key in a similar position where
+ the BACKSPACE key is located today on common PC keyboards.
+ All the terminal emulators emulated the difference between
+ these keys correctly: the backspace key generated a BACKSPACE
+ (^H) and delete key generated a DELETE (^?).
+
+ But a problem arose when Linus Torvalds wrote Linux. Unlike
+ earlier terminals, the Linux virtual terminal (the terminal
+ emulator integrated in the kernel) returned a DELETE when
+ backspace was pressed, due to the VT100 having a DELETE key in
+ the same position. This created a lot of problems (see [1]
+ and [2]). Since Linux has become the king, a lot of terminal
+ emulators today generate a DELETE when the backspace key is
+ pressed in order to avoid problems with Linux. The result is
+ that the only way of generating a BACKSPACE on these systems
+ is by using CONTROL + H. (I also think that emacs had an
+ important point here because the CONTROL + H prefix is used
+ in emacs in some commands (help commands).)
From point of view of the kernel, you can change the key
for deleting a previous character with stty erase. When you
- connect a real terminal into a machine you describe the
- type of terminal, so getty configure the correct value of
- stty erase for this terminal, but in the case of terminal
- emulators you don't have any getty that can set the correct
+ connect a real terminal into a machine you describe the type
+ of terminal, so getty configures the correct value of stty
+ erase for this terminal. In the case of terminal emulators,
+ however, you don't have any getty that can set the correct
value of stty erase, so you always get the default value.
- So it means that in case of changing the value of the
- backspace keyboard, you have to add a 'stty erase ^H' into
- your profile. Of course, other solution can be that st
- itself modify the value of stty erase. I have usually the
- inverse problem, when I connect with non Unix machines, and
- I have to press control + h to get a BACKSPACE, or the
- inverse, when a user connects to my unix machines from a
- different system with a correct backspace key.
+ For this reason, it is necessary to add 'stty erase ^H' to your
+ profile if you have changed the value of the backspace key.
+ Of course, another solution is for st itself to modify the
+ value of stty erase. I usually have the inverse problem:
+ when I connect to non-Unix machines, I have to press CONTROL +
+ h to get a BACKSPACE. The inverse problem occurs when a user
+ connects to my Unix machines from a different system with a
+ correct backspace key.
[1] http://www.ibb.net/~anne/keyboard.html
[2] http://www.tldp.org/HOWTO/Keyboard-and-Console-HOWTO-5.html
Got questions, comments, patches, etc.? Contact Jason Woofenden