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// Keyboard Device Emulation

//

// The keyboard controller code loops around until there are no more scan

// codes available from the keyboard. In real life an interrupt signal is

// generated by each scan code sent by the keyboard. There is no hardware

// buffering of scan-codes. In the emulation only a single emulation 

// interrupt is generated for a keypress(button) event and multiple scan

// codes are buffered. Rather than emulate the keyboard interface more

// closely the emulation is simplified and the driver software recognizes

// the way the emulation works. Otherwise it might be necessary to

// implement the keyboard interface in it's own thread with calls to

// Sleep() between each scan-code transmission.

// It should work because the interrupt routine checks for additional

// scan codes during it's processing. This is a case where the software

// for the system is designed around supporting the emulator.

// In real life there should never be two scan-codes sent by the keyboard

// close enough together for the loop in the keyboard code to be 

// effective. The loop is harmless enough as the scan-code status

// needs to be tested anyway. Whether its a while() or an if() is

// irrelevant.