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Let us know what is Bus first, we are going to discuss about the bus which is present in our system in which various components are present. To know more about the Computer Bus And Its Types, keep reading this article till the end you will get to know much more thing about this.

The meaning of bus in daily life is used for transportation from one place to another place, same like that in computer terms Bus is also useful for transportation of data from one place to another place which is inside a computer. So what is Bus: Bus is nothing but a set of wires which are present inside the cabinet used to connect internal components of the computer. System bus contains about fifty to hundreds of separate lines and each line has some function.

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Let us discuss about the types of buses, advantages and disadvantages and how they are connected and how they are used to connect the internal components.

Let us consider a hallow arrow which represents the bus which is used to transport the data(bits of information) from left to right or right to left. We have five functional units: Input unit, output unit, memory unit, ALU and control unit. These all combine to form all related tasks of a computer system with the help of bus they are all communicated with each other.

From input unit, the data is passed to bus and output unit will receive the data from bus, memory unit that is RAM, from memory to bus the data is bidirectional, which means two directions, and finally we have processor, from processor to bus the data is transported in bidirectional way. So this type of bus is known as single Bus. All these five units will communicated with each other using single bus. Output unit will display the information for us. All these operations will happen in seconds.

But there is a problem with single bus, the drawback is at a time only two units can communicate with each other, for example at a time only Input unit and memory unit can communicate with each other, output unit and processor cant communicate with each other. Happens the same with other components, so because of this the speed of the computer will reduce so to overcome this problem, we can use one more structure that is multiple structure,

What is multiple bus structure?

We will have more than one more bus, by using one bus we can transmit the data from input unit to memory unit and by using another bus simultaneously we can transport data from memory to processor, and from another bus, we can process the data from processor to output unit. The speed and performance will increase by using this multiple bus structure. The drawback of this is it will be difficult to implement this structure.

So there are three different types of buses:

  1. Data bus
  2. Address bus
  3. Control bus

Data bus is used to hold the data, whatever the data that a processor has to work on, and the processor is going to send that data to memory and Input/output devices. It consists of 8,32,64,128 or even so on more separate lines.

The number of lines are called as width of a data bus. Here each line carries only bit, so the width of data bus is 1 byte that is 8bits.

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Address bus indicates from where we have to send the data and from where we have to get the data. It has collection of wires these are used to identify the particular location in main memory by the CPU, it is used to identify the source or destination of data. The CPU needs to read an instruction from a given location that is in memory, so first it has to know where the data is present, so that will be informed by this address bus.

The width of a bus determines the “maximum memory capacity of a system”.

Ex: 8080 microprocessor, it has 16 bits address bus, it gives 64 k address space.

Control bus is used to monitor the data and address buses. It always monitors the system. It regulates the activities of bus, at what time the data has to be put on the data bus all these operations are performed by control bus.

It always control and timing information related to the buses, It holds signals that reports the status of various devices, whether the device is sending any data, whether the device is ready or not. So different control signals will be there in control bus like memory read, memory write, I/O read and I/O write. Memory read means It causes data from address location to be placed on the data bus.

Memory write causes data in the bus to be written on an address location executed by the CPU.

I/O read means data from I/O ports to be placed on the bus

I/O write is data on the bus to be output to the address of I/O ports.

A data bus is bidirectional, the data is sent from CPU to another devices and another devices to CPU. Address bus is uni-directional. Whereas control bus is bi-directional.

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Traditional bus architecture:

A processor is there, it is connected with some local bus which is called cache, cache is a memory unit that is present in the processor, so whatever the data the processor wants to execute, that data will be stored in the cache memory cache is the fastest storage device, local bus is there in between processor and cache device which connects both of them and there is local I/O controller connected with local bus, and the main memory and cache is connected by using system bus. The system bus is connected with some expansion bus interface.

Expansion bus slot is also connected. A network unit is also connected and modem is also there. Cache is connected to the system bus. All the devices like I/O devices and memory devices are not directly connected to processor, The processor sends the data that is stored in the cache and the cache is connected to system bus, which consists of data lines, control lines and address lines.

Local bus is also having data bus, control bus and address bus. Expansion bus is also having all these data lines and control lines and address lines. The main memory is connected to system bus and the cache.All these devices will interact with system bus.The system bus will send the data to main memory and from main memory to processor, first it has to interact with the cache and the cache will send the data to processor.

Computer organization and architecture:

The Computer organization gives the understanding about working of internal parts, structuring and how the computer system is implemented. And organization means how the system is structured so that all the tools present in are used properly.

Also read:


The architecture of computer means can be represented as tools which are seen by the user like bits which are used for data, addressing techniques and Instruction sets. And it deals with transmission of data and to tun the programs and create interactions between computers and users.

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The main components of computer organization are ALU, CPU, memory organization. Alu performs simple operations like addition, subtraction, multiplication and division. The instructions of program and data will be stored by the memory. The control unit will get the data from the memory and performs ALU’s operations and carries those instructions using that data. ALU and CU together becomes CPU(central processing unit).

The CU will send the data between the memory and I/O controller when instructions of input or output are received.

The speed of the computer is determined by the operational speed of the CPU. The CPU contains CU, ALU, registers , cache memory, buses, clock.

Registers are present in CPU these are high speed memory which are of small amounts, and processor will use these registers to store data which are of smaller amounts which are useful during processing, like:

The next instruction address should be executed

The instruction at present needs to be decoded

Calculations result.

The number of different registers are:

PC(program counter)

Memory address register(MAR)

Memory data register(MDR)

Current instruction register(CIR)


Clock is useful for coordinating all the components of the computer. The clock will send “electrical pulse” that is regular that keeps in time all the components. This frequency is called as “clock speed” its speed is measured in HERTZ(HZ).

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More instructions can be performed when their speed is greater.

I hope you have read the article on Computer Bus And Its Types and understood all the terms and concepts.

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