KEYBOARD(4)						   BSD Kernel Interfaces Manual 					       KEYBOARD(4)

NAME

     keyboard -- pc keyboard interface

DESCRIPTION

     The PC keyboard is used as the console character input device.  The keyboard is owned by the current virtual console.  To switch between the
     virtual consoles use the sequence ALT+Fn, which means hold down ALT and press one of the function keys.  The virtual console with the same
     number as the function key is then selected as the current virtual console and given exclusive use of the keyboard and display.

     The console allows entering values that are not physically present on the keyboard via a special keysequence.  To use this facility press and
     hold down ALT, then enter a decimal number from 0-255 via the numerical keypad, then release ALT.	The entered value is then used as the
     ASCII value for one character.  This way it is possible to enter any ASCII value, not present on the keyboard.  The console driver also
     includes a history function.  It is activated by pressing the scroll-lock key.  This holds the display, and enables the cursor arrows for
     scrolling up and down through the last scrolled out lines.

     The keyboard is configurable to suit the individual user and the different national layout.

     The keys on the keyboard can have any of the following functions:

     Normal key    Enter the ASCII value associated with the key.
     Function key  Enter a string of ASCII values.
     Switch Key    Switch virtual console.
     Modifier Key  Change the meaning of another key.

     The keyboard is seen as a number of keys numbered from 1 to n.  This number is often referred to as the "scancode" for a given key.  The num-
     ber of the key is transmitted as an 8 bit char with bit 7 as 0 when a key is pressed, and the number with bit 7 as 1 when released.  This
     makes it possible to make the mapping of the keys fully configurable.

     The meaning of every key is programmable via the PIO_KEYMAP ioctl call, that takes a structure keymap_t as argument.  The layout of this
     structure is as follows:

			   struct keymap {
				   u_short n_keys;
				   struct key_t {
					   u_char map[NUM_STATES];
					   u_char spcl;
					   u_char flgs;
				   } key[NUM_KEYS];
			   };

     The field n_keys tells the system how many keydefinitions (scancodes) follows.  Each scancode is then specified in the key_t substructure.

     Each scancode can be translated to any of 8 different values, depending on the shift, control, and alt state.  These eight possibilities are
     represented by the map array, as shown below:

								 alt
      scan			    cntrl	   alt	  alt	cntrl
      code     base   shift  cntrl  shift   alt   shift  cntrl	shift
      map[n]	  0	  1	 2	3     4       5      6	    7
      ----     ------------------------------------------------------
      0x1E	'a'	'A'   0x01   0x01    'a'    'A'   0x01	 0x01

     This is the default mapping for the key labelled 'A' which normally has scancode 0x1E.  The eight states are as shown, giving the 'A' key its
     normal behavior.  The spcl field is used to give the key "special" treatment, and is interpreted as follows.  Each bit corresponds to one of
     the states above.	If the bit is 0 the key emits the number defined in the corresponding map[] entry.  If the bit is 1 the key is "special".
     This means it does not emit anything; instead it changes the "state".  That means it is a shift, control, alt, lock, switch-screen, function-
     key or no-op key.	The bitmap is backwards i.e., 7 for base, 6 for shift etc.

     The flgs field defines if the key should react on caps-lock (1), num-lock (2), both (3) or ignore both (0).

     The kbdcontrol(1) utility is used to load such a description into/outof the kernel at runtime.  This makes it possible to change the key
     assignments at runtime, or more important to get (GIO_KEYMAP ioctl) the exact key meanings from the kernel (e.g. used by the X server).

     The function keys can be programmed using the SETFKEY ioctl call.

     This ioctl takes an argument of the type fkeyarg_t:

			   struct fkeyarg {
				   u_short keynum;
				   char    keydef[MAXFK];
				   char    flen;
			   };

     The field keynum defines which function key that is programmed.  The array keydef should contain the new string to be used (MAXFK long), and
     the length should be entered in flen.

     The GETFKEY ioctl call works in a similar manner, except it returns the current setting of keynum.

     The function keys are numbered like this:

		   F1-F12		   key 1 - 12
		   Shift F1-F12 	   key 13 - 24
		   Ctrl F1-F12		   key 25 - 36
		   Ctrl+shift F1-F12	   key 37 - 48

		   Home 		   key 49
		   Up arrow		   key 50
		   Page Up		   key 51
		   (keypad) -		   key 52
		   Left arrow		   key 53
		   (keypad) 5		   key 54
		   Right arrow		   key 55
		   (keypad) +		   key 56
		   End			   key 57
		   Down arrow		   key 58
		   Page down		   key 59
		   Insert		   key 60
		   Delete		   key 61

		   Left window		   key 62
		   Right window 	   key 63
		   Menu 		   key 64

     The kbdcontrol(1) utility also allows changing these values at runtime.

AUTHORS

     Soren Schmidt <sos@FreeBSD.org>

BSD
								  January 8, 1995							       BSD