Programs which I wrote

This is a game called X Labyrinth - the aMAZEment: it works under any UNIX system with X windows (at least, I have tested it under Linux and SunOS). The goal of the game is to solve a maze with your mouse; but the fun part is that the walls of the maze actually block the mouse. It is distributed under the terms of the GNU General Public License.

I have also written a program called SIMPLE - Simple Is a Macro Processing Language Element. You can learn more about SIMPLE here.

Apart from that, the only thing I have are two programs, called record.c and playback.c which will record and play raw sound files through /dev/dsp.

For my other programs, check my programs page.

Setup and all that

Keyboard questions

To summarize: when the key is pressed, the keyboard sends a scan code on one of the ports, and the CPU receives an interruption (IRQ1 I think). The linux kernel receives the interruption, reads the scan code, and converts it to a key code. Finally, this key code is turned to an ascii character which is read by whatever process is running. Unfortunately, thins aren't that simple. First of all, the keyboard knows three different ways of converting keys to scan codes, called scan tables 1, 2 and 3. Scan table 3 is the most logical one (well... sort of), and it has many advantages (for example, every key has programmable auto-repeat, which is not the case for the other scan tables, and also every key sends one and exactly one byte of scan code); however, this is NOT the table used by the linux kernel: it uses scan table 2. Second, the keyboard can be used in four modes: raw mode (in which /dev/console returns scan codes), semi-raw mode (in which key codes are returned), and translated mode (in which ascii characters are produced). [Note that this has nothing to do with the "raw" and "cooked" modes which refer to the way a process will receive control characters.] The keyboard mode can be read and modified using kbd_mode. Third, X sets the keyboard in raw mode, and does its own three-step translation: from scan codes to key codes, from key codes to keysyms and from keysyms to ascii characters. To make things simpler, the key codes produced by X are NOT the same as those produced by the linux kernel when keyboard is in semi-raw mode (and this is not for compatibility with other X platforms since the keycodes are also different, e.g., on a sun keyboard). Keysyms, however, are universal. The key "a" will have the same keysym on a QWERTY or AZERTY keyboard (if the xmodmap is correctly set, that is...). The list of supported keysyms (16-bit integers) can be found in one of the X11 include files, I never know which. The translation from keysyms to ascii codes is done by XLookupString, but I never understood how this one works. So we can summarize all this with the following picture:

key pressed
    | [Inside keyboard; 3 possible tables]
    v
scan code [Stops here if keyboard mode is raw]
    |
    +----------------------------+
    | [Linux kernel]             | [X11]
    v                            v
linux keycode                 X11 keycode
    | [loadkeys]                 | [xmodmap]
    v                            v
ascii character(s)/action     keysym
    | [running process]          | [wm might intercept]
    v                            v
whatever                      keysym if not intercepted by wm
                                 | [program]
                                 v
                              whatever

Concerning backspace and delete

For historical reasons, I guess, there are two control characters which mean "erase the last character": ^H (ascii character 0x08=8) and ^? (ascii character 0x7f=127). There is no control character which says "erase the next character", because erasing the next character (the one under the cursor) implies you were able to move the cursor, so you must have very sophisticated line-editing capabilities, so if you have a convention for sending the arrow keys you can probably use that convention for the delete key too. The VT escape sequence for "delete next char" is ^[[3~ (escape (0x1b) open bracket three tilde). When there are no line editing capabilites, foe example in the primitive shells like the original sh and csh, the only possible action is "erase the character on the left". Exactly which control character will do that is specified using stty (for example stty erase "^H" specifies that ^H should be used). This is not always correctly set: sometimes the backspace key sends ^H whereas the last-character-correction key is ^? (the converse is less frequent). This should be corrected with stty. Unfortunately, some X11 systems correct this by using xmodmap instead, thus assigning the BackSpace keysym to the delete key, and the Delete keysym to the backspace key. Since X-oriented programs like netscape read keysyms and not ascii characters (and even less pay attention to the state of stty), this has the pernicious effect of inverting the backspace and delete keys under these programs. I suggest using ^H for backspace (that is, putting a line like

keycode  14 = BackSpace        BackSpace

keycode 22 = BackSpace

if [ -f .xmodmaprc ]; then
        xmodmap .xmodmaprc &
fi

Table of (some) keys found on (some) keyboards

Key engraving/name	Scan 1	Scan 2	Scan 3	Linux keycode	X keycode
Escape	0x76	0x01	0x08	1	1
F1	0x05	0x3b	0x07	59	67
F2	0x06	0x3c	0x0f	60	68
F3	0x04	0x3d	0x17	61	69
F4	0x0c	0x3e	0x1f	62	70
F5	0x03	0x3f	0x27	63	71
F6	0x0b	0x40	0x2f	64	72
F7	0x83	0x41	0x37	65	73
F8	0x0a	0x42	0x3f	66	74
F9	0x01	0x43	0x47	67	75
F10	0x09	0x44	0x4f	68	76
F11	0x78	0x57	0x56	87	95
F12	0x07	0x58	0x5e	88	96
Print Screen	0xe0 0x12 0xe0 0x7c	0xe0 0x2a 0xe0 0x37	0x57	99	111
Scroll Lock	0x7e	0x46	0x5f	70	78
Pause	0xe1 0x14 0x77 0xe1	0xe1 0x1d 0x45 0xe1	0x62	119/101	110
`~	0x0e	0x29	0x0e	41	49
1!	0x16	0x02	0x16	2	10
2@	0x1e	0x03	0x1e	3	11
2@	0x1e	0x03	0x1e	3	11
3#	0x26	0x04	0x26	4	12
4$	0x25	0x05	0x25	5	13
5%	0x2e	0x06	0x2e	6	14
=+	0x55	0x0d	0x55	13	21
Backspace	0x66	0x0e	0x66	14	22
Tab	0x0d	0x0f	0x0d	15	23
Q	0x15	0x10	0x15	16	24
W	0x1d	0x11	0x1d	17	25
]}	0x5b	0x1b	0x5b	27	35
\|	0x5d	0x2b	0x5c	43	51
Caps lock	0x58	0x3a	0x14	58	66
A	0x1c	0x1e	0x1c	30	38
'"	0x52	0x28	0x52	40	48
Enter	0x5a	0x1c	0x5a	28	36
Shift (left)	0x12	0x2a	0x12	42	50
Z	0x1a	0x2c	0x1a	86	94
Shift (right)	0x59	0x36	0x59	54	62
Control (l)	0x14	0x1d	0x11	29	37
Winlogo (l)	?	?	?	125	115
Alt (l)	0x11	0x38	0x19	56	64
Space bar	0x29	0x39	0x29	57	65
Alt (r)	0xe0 0x11	0xe0 0x38	0x39	100	113
Winlogo (r)	?	?	?	126	116
Winmenu	?	?	?	127	117
Control (r)	0xe0 0x14	0xe0 0x1d	0x58	97	109

Configuration files

I reinstalled Linux on both of my computers recently (I have a PPro200 called ``pleiades'' and a 486DX33 called ``sirius'', connected by a local ethernet - the modem is on sirius and that is its main use). I have kept a log of everything I did as root, and here it is if it can be of use to anyone:

• on pleiades
• on sirius

Coming soon on this page: a tar.gz archive of my /etc directories (minus a few confidential files, of course).