@node bioskey, bios
@subheading Syntax

@example
#include <bios.h>

int bioskey(int command)
@end example

@subheading Description

This function issues the BIOS keyboard interrupt 16h with @var{command}
in the @sc{ah} register, and returns the results of that call.  The
argument @var{command} can accept the following values:

@table @asis

@item @var{command} = 0

Returns the next key pressed.  The value returned is a combination of
the key's scan code in the high 8 bits and its ASCII code in the low 8
bits.

@item @var{command} = 1

Checks the keyboard, returns zero if no key pressed, else the key.  Does
not dequeue the key from the keyboard buffer.  The value returned when a
key was pressed is a combination of the key's scan code in the high 8
bits and its ASCII code in the low 8 bits.

If the @kbd{Ctrl-@key{BREAK}} key was pressed, returns -1.

@item @var{command} = 2

Returns the shift state:

@example
7654 3210  Meaning

---- ---X  Right shift key down
---- --X-  Left shift key down
---- -X--  Ctrl key down
---- X---  Alt key down
---X ----  Scroll lock on
--X- ----  Num lock on
-X-- ----  Caps lock on
X--- ----  Insert on
@end example

@item @var{command} = 10

Returns the next extended key pressed.  This works like the case of
@var{command} = 0, but it recognizes additional keys from the AT-style
extended 101-key keyboard, like the second @key{Alt} key and @key{F12}.
If a key was pressed, returns the scan code and ASCII code packed in
same way as for @var{command} = 0.

Almost every PC nowadays has an extended 101-key keyboard.

@item @var{command} = 11

Like the case of @var{command} = 1, but recognizes the additional keys
of the extended keyboard.

@item @var{command} = 12

Returns the two status bytes of the enhanced keyboard, packed in the low
16 bits of the return value.  The individual bits of the return value
are defined in the following table:

@example
FEDC BA98  7654 3210  Meaning
---- ----  ---- ---X  Right SHIFT is pressed
---- ----  ---- --X-  Left SHIFT is pressed
---- ----  ---- -X--  CTRL is pressed
---- ----  ---- X---  ALT is pressed
---- ----  ---X ----  Scroll Lock locked
---- ----  --X- ----  Num Lock locked
---- ----  -X-- ----  Caps Lock locked
---- ----  X--- ----  Insert locked

---- ---X  ---- ----  Left CTRL is pressed
---- --X-  ---- ----  Left ALT is pressed
---- -X--  ---- ----  Right CTRL is pressed
---- X---  ---- ----  Right ALT is pressed
---X ----  ---- ----  Scroll Lock is pressed
--X- ----  ---- ----  Num Lock is pressed
-X-- ----  ---- ----  Caps Lock is pressed
X--- ----  ---- ----  SysReq is pressed
@end example

@end table

@subheading Return Value

Depends on @var{command}.

@subheading Portability

@portability !ansi, !posix

@subheading Example

@example
while (!bioskey(1))
  do_stuff();
@end example