A bus: We know that a circuit is always from the components connected through the wire in analog circuits, the connection does not become a problem because the devices are usually serial inter-relationship between the various devices connection, not many, but not the same as computer circuits, which is based on the microprocessor as the core, the device must be connected with the microprocessor, the device must be between the coordinated and so they need a lot of connections on If still the same as analog circuits, in the microprocessor and a separate connection between devices, while the number of lines will be more shocking, so the introduction of the microprocessor in the concept of a bus, all devices share the connection, all devices all the eight data lines from the eight common line, which is equivalent to all devices in parallel, but this is not enough alone, if there are two devices send data at the same time, a 0, a 1, then recipient received what is it? This is not allowed, there is a need to control through the control line so that devices work time, any time there can be only one device to send data (can have more than one receiving device at the same time). Data devices will be referred to as data bus, all the line of control devices known as the control bus. In the internal or external memory single-chip and other devices in the memory cell, the memory cell to be assigned addresses to use, the allocation of addresses is of course given in the form of electrical signals, and as a result of more storage units, so for address the allocation of more of the line, the line known as the address bus.