What happened when we hit a keyboard?

What happened when we hit a keyboard?

When we hit keyboard Hardware interrupt 9 is called by system. Then the BIOS software interrupt 16 is called and this routine will execute. This interrupt routine will store our keyboard information into a specified memory location called Bios data area (BIOS Data Area at 0x0040:0x0000.). After this, a signal is returned back to keyboard. (This signal is used to switch on/of the number lock, caps Lock LED’s etc).

The keyboard information is stored at following location. 0x0040:0x17 2 bytes Keyboard status flag 0x0040:0x19 1 bytes Alt + Numpad data 0x0040:0x1A 2 bytes Keyboard buffer head 0x0040:0x1C 2 bytes Keyboard buffer tail 0x0040:0x1E 32 bytes Keyboard buffer

For Example: To find our CapsLock status. 6th Bit of 0x0040:0x17 will indicate current status of CapsLock. If 0 = CapsLock off ,if  1 - CapsLock on.