Input & Output Devices
Peripheral devices are external devices that connect to the computer through ports, such as USB, Ethernet, and parallel ports. When hardware is installed inside or outside a computer, the operating system needs a special piece of software called a driver to help it understand how to communicate with that device. Drivers either come with new hardware when it is purchased or can be downloaded from the manufacturer's website.
Inside the computer on the motherboard there are slots where other boards, usually called cards, are inserted to allow the computer's functionality to be expanded. These cards often include a port into which a peripheral can be plugged. An example of a peripheral is a monitor, keyboard, or mouse. Each of these components is plugged into the back of the computer case. The CPU knows they are there because the card associated with that peripheral tells it. The number of internal expansion slots a computer has is an indication to how easily the computer can be upgraded. It is important to understand the different types of peripherals and what their main uses are in case you need to add a device to your computer. A small PC might fit well on or under your desk, but if you can't upgrade it later or if the processor runs too hot because of inadequate cooling, you may have to replace the entire computer.
One classification of peripherals is input devices. Input devices are the parts that bring information into the computer, like the keyboard, mouse, microphone, and scanner. The input device translates human actions or physical objects (analog data) into an electronic (digital) form the computer can recognize. Other common input devices are joysticks, bar code readers, cameras, fingerprint readers, etc. CD and DVD drives are also input devices, since they read data into the computer.
Another classification of a peripheral is an output device. Output devices translate information stored in the computer and present it in a way that humans can understand it. Typical output devices in a computer system are the monitor, speakers and the printer.
Some devices that perform both input AND output operations are referred to as I/O (input/output) devices and their operations are called I/O operations. Examples of common input and output components are disk drives and modems. A touch screen monitor on an ATM or a videogame controller that shakes when the player is hit can both be considered an I/O device. A CD or DVD burner would also be an I/O device, since it can both read and write data to discs.