In order for a personal computer to be useful, it must have channels for receiving input from the user and channels for delivering output to the user. Input and output devices connect to the computer through connection ports, which are generally part of the motherboard and are accessible outside the computer case. In early personal computers, specific ports were designed for each type of output device. The configuration of these ports has evolved over the years, becoming more and more standardized over time. Today, almost all devices plug into a computer through the use of a USB port. This has increased in its capabilities, both in its data transfer rate and power supplied.
Besides USB, some input and output devices connect to the computer via a wireless-technology standard called Bluetooth, which was invented in 1994. Bluetooth exchanges data over short distances of 10 meters up to 100 meters using radio waves. Two devices communicating with Bluetooth must both have a Bluetooth communication chip installed. Bluetooth devices include pairing your phone to your car, computer keyboards, speakers, headsets, and home security, just to name a few.
All personal computers need components that allow the user to input data. Early computers simply used a keyboard for entering data or selecting an item from a menu to run a program. With the advent of operating systems offering the graphical user interface, the mouse became a standard component of a computer. These two components are still the primary input devices to a personal computer, though variations of each have been introduced with varying levels of success over the years. For example, many new devices now use a touch screen as the primary way of data entry.
Other input devices include scanners which allow users to input documents into a computer either as images or as text. Microphones can be used to record audio or give voice commands. Webcams and other types of video cameras can be used to record video or participate in a video chat session.
Output devices are essential as well. The most obvious output device is a display or monitor, visually representing the state of the computer. In some cases, a personal computer can support multiple displays or be connected to larger-format displays such as a projector or large-screen television. Other output devices include speakers for audio output and printers for hardcopy output.