The bus is a set of connection between two or more components/devices which design to transfer several bits of a word from. It consist of a set of parallel wires or tines to which a CPU, memory and all input/output devices are connected to transmit 8 bits, 8 lines are required in addition same other lines are also needed for controlling this transfer

• The bus can be unique directional (transmition of data can be only in one direction) or by directional (transmition of data can be in both direction)
• A bus that connect to all the three components (cpu, memory and output devices) is called a sustem bus, a system bus consist of 50-100 separate lines.

1.Data bus

It provide a path for moving data between the system medium. This are collectively known as data bus, normally, a data bus consist of 8, 16, or 32 separate line. The number of lines present in a data bus is called the width of data bus and limits the maximum number of bits that can be transfer simultnewsly.

2.Address line

It is use to designate the source of data for data bus. For reading or writing, any information on the memory, the cpu need to specify the address of a particular location. The width of the address bus specifies the maximum possible memory supported by a system e.g. if a system has 16 bits while address bus it can support memory sizes equal to 2/16 (65536 bit).

3.Control bus

Control lines are used to control the access to data and control bus. This is required as bus is a shared medium. The lines are used for the transmission of commands and timing signals (with validates data) between the system module. Timing signal indicates whether data and address is valid whereas command signals specify which operation is to be performed.

Processor to memory communication

Communication between the processor and memory can be

• Transfers of information from the memory to the processor
• Write information in the memory

Processor to I/O communication

I/O units are connective to the computer through the system. Each I/O device first mit with a controller called DMA (direct memory access) controller, which contracts the operation of that device. The DMA controller is connected to the buses and can directly access memory and is used to transport one memory to location to another, or form one I/O device to memory and vice versa.