Keyboard comes in many styles or layouts. The various models differ from shape, size and feel. Among the IBM compatible computers, the most common keyboard layout is the IBM Enhanced Keyboard. It has about 100-104 keys on it. There are seven groups of keys.
When we press a key, a tiny chip in the keyboard called keyboard controller notes that a key has been pressed. Keyboard controller places a coed in the buffer of the keyboard to indicate which key was pressed. Keyboard buffer is a temporary memory of the keyboard controller. The keyboard controller sends a signal to the system software notifying that something happened at the keyboard.
As it’s name implies, input devices are devices which can send signals to the CPU. That means, the device we use to send or enter a signal or data to CPU are called input device, such as; keyboard, mouse, microphone etc.