To function, hardware requires physical connections that allow components to communicate and interact. A bus provides a common interconnected system composed of a group of wires or circuitry that
coordinates and moves information between the internal parts of a computer.
A bus is characterized by two features: how much information it can manipulate at one time, called the bus width, and how quickly it can
transfer these data.
A serial connection
A serial connection is a wire or set of wires used to transfer information from the CPU to an external device such as a mouse, keyboard, modem, scanner, and some types of printers.
This type of connection transfers only one piece of data at a time and is therefore slow. The advantage of using a serial connection is that it provides effective connections over long distances.
A parallel connection
A parallel connection uses multiple sets of wires to transfer blocks of information simultaneously. Most scanners and printers use this type of connection. A parallel connection is much faster than a serial connection, but it is limited to distances of less than 3 m (10 ft) between the CPU and the external device.