A bus is a collection of wires used to transmit signals in parallel. The major parts of microcomputers are central processing unit (CPU), memory, and input and output unit. To connect these parts together through three sets of parallel lines, called buses. According to the purpose, the buses of a microcomputer can be divided into three types: address bus, data bus, and control bus.
Address bus
Address bus is a computer bus (a series of lines connecting two or more devices) that is used to specify a physical address. When a processor needs to read or write to a memory location, it specifies that memory location on the address bus (the value to be read or written is sent on the data bus). The width of the address bus determines the amount of memory a system can address. For example, a system with a 32-bit address bus can address 232 (4,294,967,296) memory locations. If each memory location holds one byte, the addressable memory space is 4 GB.
Data bus
A data bus is a system within a computer or device, consisting of a connector or set of wires, that provides transportation for data. Different kinds of data buses have evolved along with personal computers and other pieces of hardware.
Control bus
The control bus is used to transmit the control signals such as read, write, and interrupt control signal. While the address bus carries the information on which device the CPU is communicating with and the data bus carries the actual data being processed, the control bus carries commands from the CPU and returns status signals from the devices.
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