Add info about Backspace and Delete to the FAQ

Here is a modest attempt at cleaning it up a little bit. I changed a
few phrases that seemed awkward, but I think the content is the same.

--
Wolfgang Corcoran-Mathe

Signed-off-by: Roberto E. Vargas Caballero <k0ga@shike2.com>
master
Wolfgang Corcoran-Mathe 2014-07-25 13:32:29 -04:00 committed by Roberto E. Vargas Caballero
parent f210ea26c4
commit e8f3513bf4
1 changed files with 42 additions and 43 deletions

85
FAQ
View File

@ -104,54 +104,53 @@ This is an issue that was discussed in suckless mailing list
<http://lists.suckless.org/dev/1404/20697.html>: <http://lists.suckless.org/dev/1404/20697.html>:
Well, I am going to comment why I want to change the behaviour Well, I am going to comment why I want to change the behaviour
of this key. When ascii was defined in 1968 communication of this key. When ASCII was defined in 1968, communication
with computers were done using punched cards, or hardcopy with computers was done using punched cards, or hardcopy
terminals (basically a typewritter machine connected with terminals (basically a typewriter machine connected with the
the computer using a serial port). Due to this, ascii defines computer using a serial port). ASCII defines DELETE as 7F,
DELETE as 7F, because in the puched cards, it means all the because, in punched-card terms, it means all the holes of the
holes of the card punched, so it is a kind of 'phisical card punched; it is thus a kind of 'physical delete'. In the
delete'. In the same way, BACKSPACE key was a non destructive same way, the BACKSPACE key was a non-destructive backspace,
back space, as in typewriter machines. So, if you wanted as on a typewriter. So, if you wanted to delete a character,
to delete a character, you had to BACKSPACE and then DELETE. you had to BACKSPACE and then DELETE. Another use of BACKSPACE
Other use of BACKSPACE was accented characters, for example was to type accented characters, for example 'a BACKSPACE `'.
'a BACKSPACE `'. The VT100 had no BACKSPACE key, it was The VT100 had no BACKSPACE key; it was generated using the
generated using the CONTROL key as another control character CONTROL key as another control character (CONTROL key sets to
(CONTROL key sets to 0 b7 b6 b5, so it converts H (code 0 b7 b6 b5, so it converts H (code 0x48) into BACKSPACE (code
0x48) into BACKSPACE (code 0x08)), but it had a DELETE key 0x08)), but it had a DELETE key in a similar position where
in a similar position where BACKSPACE key is located today the BACKSPACE key is located today on common PC keyboards.
in common PC keyboards. All the terminal emulators emulated All the terminal emulators emulated the difference between
correctly the difference between these keys, and backspace these keys correctly: the backspace key generated a BACKSPACE
key generated a BACKSPACE (^H) and delete key generated a (^H) and delete key generated a DELETE (^?).
DELETE (^?).
But the problem arised when Linus Torvald wrote Linux, and But a problem arose when Linus Torvalds wrote Linux. Unlike
he did that the virtual terminal (the terminal emulator earlier terminals, the Linux virtual terminal (the terminal
integrated in the kernel) returns a DELETE when backspace emulator integrated in the kernel) returned a DELETE when
was pressed, due to the fact of the key in that position backspace was pressed, due to the VT100 having a DELETE key in
in VT100 was a delete key. This created a lot of problems the same position. This created a lot of problems (see [1]
(you can see it in [1] and [2]), and how Linux became the and [2]). Since Linux has become the king, a lot of terminal
king, a lot of terminal emulators today generate a DELETE emulators today generate a DELETE when the backspace key is
when backspace key is pressed in order to avoid problems pressed in order to avoid problems with Linux. The result is
with linux. It causes that the only way of generating a that the only way of generating a BACKSPACE on these systems
BACKSPACE in these systems is using CONTROL + H. I also is by using CONTROL + H. (I also think that emacs had an
think that emacs had an important point here because CONTROL important point here because the CONTROL + H prefix is used
+ H prefix is used in emacs in some commands (help commands). in emacs in some commands (help commands).)
From point of view of the kernel, you can change the key From point of view of the kernel, you can change the key
for deleting a previous character with stty erase. When you for deleting a previous character with stty erase. When you
connect a real terminal into a machine you describe the connect a real terminal into a machine you describe the type
type of terminal, so getty configure the correct value of of terminal, so getty configures the correct value of stty
stty erase for this terminal, but in the case of terminal erase for this terminal. In the case of terminal emulators,
emulators you don't have any getty that can set the correct however, you don't have any getty that can set the correct
value of stty erase, so you always get the default value. value of stty erase, so you always get the default value.
So it means that in case of changing the value of the For this reason, it is necessary to add 'stty erase ^H' to your
backspace keyboard, you have to add a 'stty erase ^H' into profile if you have changed the value of the backspace key.
your profile. Of course, other solution can be that st Of course, another solution is for st itself to modify the
itself modify the value of stty erase. I have usually the value of stty erase. I usually have the inverse problem:
inverse problem, when I connect with non Unix machines, and when I connect to non-Unix machines, I have to press CONTROL +
I have to press control + h to get a BACKSPACE, or the h to get a BACKSPACE. The inverse problem occurs when a user
inverse, when a user connects to my unix machines from a connects to my Unix machines from a different system with a
different system with a correct backspace key. correct backspace key.
[1] http://www.ibb.net/~anne/keyboard.html [1] http://www.ibb.net/~anne/keyboard.html
[2] http://www.tldp.org/HOWTO/Keyboard-and-Console-HOWTO-5.html [2] http://www.tldp.org/HOWTO/Keyboard-and-Console-HOWTO-5.html