What Happens When You Press A Key
To illustrate how the computer works, let's take a very simple example. Let's suppose you are working in your word processor and you type the letter "M". Here's what happens, in general terms, when you press the " M " button: The keyboard sends an electrical signal, called a scan code, to the computer saying that a button was pressed. The keyboard controller interprets the scan code and determines that the letter pressed was an " M ". It stores this " M " in a special memory location until the processor is ready to deal with it. The controller sends a signal to the processor, called an interrupt. An interrupt tells the processor that some part of the computer has information for it to process and wants its attention. In this case, the keyboard controller wants the processor to look at the key you just pressed. The processor is almost always doing many things, sharing its time among many tasks. As a result, most every event must wait i...