Short for Universal Serial Bus, USB provides a standardized way to connect peripherals to computers and other electronics. Since its original release in 1995, USB has become ubiquitous, replacing numerous other types of connections and, as of June 2014, it works with over 10 billion PCs and devices. USB works on all major operating systems -- Windows, Mac OS X and Linux -- and almost every computer, whether desktop or laptop, has at least one USB port.
A Universal Connector
Prior to USB, computers used a range of different types of peripheral ports. Printers connected via the parallel port, game controllers via the game port, other devices via the serial port, and so on. As most computers only had one of each type of port, it was difficult to manage large numbers of peripherals -- especially as connected devices could cause conflicts with each other. With USB, all of these devices use the same connector without conflicting in the system.
Types of USB Devices
Most types of computer peripherals use USB. Printers, game controllers, cameras, external hard drives and flash memory sticks all connect through USB, with some exceptions, such as Thunderbolt devices for Macs. Even types of devices that normally use alternate ports -- such as the 3.5mm port for headphones or the DVI port for monitors -- have some models that work via USB. Mice and keyboards also frequently use USB, though most desktop computers also still support the older PS/2 connector.
USB supports hot-swapping, which allows you to connect and disconnect USB devices without rebooting your computer. In comparison, many other ports only identify new connections during startup. All major operating systems have built-in support for USB 2.0 (and USB 3.0, beginning with Windows 8), so you won't need to install software to use USB. Some individual devices still require you to install drivers, but many -- including most mice, keyboards, hard drives and USB drives -- work automatically.
USB has gone through three major versions, with each improving the maximum speed of data transfer: 1.5 megabits per second over USB 1, 480Mbps for USB 2 and 5 gigabits per second on USB 3. A revision, USB 3.1, pushes this speed to 10Gbps. In order for a device to run at USB 3 speeds, all parts -- peripheral, cable and USB port -- must support the USB 3 standard. Other than speed, however, the versions are backward compatible, allowing you to connect USB 2 devices to a USB 3 port and vice versa.