- Computer keyboards are an input device. They put the information a person types into a program on the computer. Most keyboards have 80 to 110 keys. The numbers and letters on the keyboard are displayed keycaps--these are the buttons that are pressed when a person types. The layout of the numbers and letters are the same on every keyboard and they are referred to as the QWERTY.
- The inside of the keyboard is like a mini-computer and consists of a processor and circuits. These transfer the information to the processor inside of the computer. Inside of the keyboard's processor resides the key matrix. The key matrix is a grid of circuits. These circuits are individually placed under each key. When a key is pushed, it pushes the switch on the circuit board underneath the key causing an electrical current to pass through the circuit and into the processor. When the current passes through, the switch vibrates, signaling the processor to read it.
- The circuit is closed when a key is pressed. The closing of the circuit signals the processor to read the keymap stored within it. The processor uses the keymap, sometimes called the character map, to find the key that is closed off on the board. By using the keymap, the processor in the keyboard can tell which letter is being pushed and if it should be a capital or lowercase letter depending on if the shift key is being pressed.
- The keyboard connects to the computer via a five pin male plug or a PS/2 plug. Keyboards and computers work together in a bi-directional format. This means that they can each send information to one another. These bi-directional lines are the clock line coming from the keyboard and the data line coming from the computer. Both lines must be idle, or high in order for the keyboard to send data. The computer will send a signal to the keyboard through the clock line letting it know that the line is clear to send. If the line is not clear, the keyboard will hold the information until the line opens. When the line is low, the keyboard is waiting for a command from the computer. When the computer wants to send information to the keyboard, it brings the data and the clock line low. It does this to ensure that the keyboard does not send it a message at the same time.
