The Microsoft® Windows® keyboard driver processes all keyboard input for Windows and Windows applications. It directly accesses the keyboard hardware, yet provides hardware-independent keyboard input by translating scan codes to virtual-key codes.
The Windows keyboard driver consists of the following:
Windows requires the keyboard to generate an interrupt whenever the user presses or releases a key. In response to an interrupt, the driver's keyboard-interrupt handler translates corresponding scan codes (and corresponding shift state) to Windows virtual-key codes. The keyboard passes both scan codes and virtual-key codes to Windows for generating keyboard messages, or for initiating some other action.