@node _bios_keybrd, bios
@subheading Syntax

@example
#include <bios.h>

unsigned _bios_keybrd(unsigned cmd);
@end example

@subheading Description

The _bios_keybrd routine uses INT 0x16 to access the keyboard
services. The @var{cmd} argument can be any of the following
manifest constants:

@table @code

@item _KEYBRD_READ

Read the next key pressed

@item _NKEYBRD_READ

Read the next extended key pressed

@item _KEYBRD_READY

Check if the next key in the keyboard buffer

@item _NKEYBRD_READY

Check if the next extended key in the keyboard buffer

@item _KEYBRD_SHIFTSTATUS

Read keyboard shift state (0x0040:0x0017 byte):

@example
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
@end example

@item _NKEYBRD_SHIFTSTATUS

Read keyboard shift and extended shift state (0x0040:0x0017 word):

@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

Return Value

With the ???_READ and ???_SHIFTSTATUS arguments, the _bios_keybrd
function returns the contents of the AX register after the BIOS
call.

With the ???_READY argument, _bios_keybrd returns 0 if there is no
key. If there is a key, _bios_keybrd returns the key waiting to be
read (that is, the same value as _KEYBRD_READ).

With the ???_READ and ???_READY arguments, the _bios_keybrd function
returns -1 if CTRL+BREAK has been pressed and is the next keystroke
to be read.

@subheading Portability

@portability !ansi, !posix

@subheading Example

@example
while( !_bios_keybrd(_KEYBRD_READY) )
  try_to_do_something();
@end example