_bios_keybrd

Syntax

#include <bios.h>

unsigned _bios_keybrd(unsigned cmd);

Description

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

_KEYBRD_READ

Read the next key pressed

_NKEYBRD_READ

Read the next extended key pressed

_KEYBRD_READY

Check if the next key in the keyboard buffer

_NKEYBRD_READY

Check if the next extended key in the keyboard buffer

_KEYBRD_SHIFTSTATUS

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

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

_NKEYBRD_SHIFTSTATUS

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

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

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.

Example

while( !_bios_keybrd(_KEYBRD_READY) )
  try_to_do_something();

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