Add info about Backspace and Delete to the FAQ

diff --git a/FAQ b/FAQ
index adac39f..2ee5ec7 100644 (file)
--- a/FAQ
+++ b/FAQ
@@ -98,3 +98,61 @@ If you want to compile st for OpenBSD you have to remove -lrt from config.mk, an
 st will compile without any loss of functionality, because all the functions are
 included in libc on this platform.
 
 st will compile without any loss of functionality, because all the functions are
 included in libc on this platform.
 

+## Backspace key does not work
+
+This is an issue that was discussed in suckless mailing list
+<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).
+
+       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
+       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.
+
+       [1] http://www.ibb.net/~anne/keyboard.html
+       [2] http://www.tldp.org/HOWTO/Keyboard-and-Console-HOWTO-5.html
+