Block Diagram of a Computer | How a computer works?

In this article, we will learn how a computer works using a block diagram of a computer and its various components.

In the world of technology and innovations upgrading rapidly, computers have become part of our daily lives.

These days, computers are doing everything from performing basic operations like watching a TV show/movie to advancing functions like manufacturing a car, and weather forecasting.

But have you ever thought about how a computer works? What processes take place? What are the fundamentals of a computer? The computer has also a basic architecture just like the other machines/devices. It comprises various elements which process the input and produce the desired output.

Block Diagram of a Computer

Let us look at the basic block diagram of the computer. Then, we will understand how each element contributes to its functioning.


All the data received by the computer goes through the input unit. The input unit includes different devices like a mouse, keyboard, scanner, etc. In other words, each of these devices acts as a mediator between the users and the computer.

The data is accepted through the input unit(raw data) in binary form. It then processes the data and produces the desired output.

The 3 major functions of the input unit are-

  • Take the data to be processed by the user.
  • Convert the given data into a machine-readable form(binary form).
  • And then, transmit the converted data into the computer’s main memory. The only purpose is to connect the user and the computer.

CPU – Central Processing Unit

C.P.U is the brain of the computer and without a CPU, the computer is nothing but a scrap. It works the same way a human brain works. Just like the brain controls all activities of the body organs, the CPU too controls all tasks for processing the data.

Moreover, the CPU performs all the arithmetical and logical operations in the computer.

Now the CPU includes two units, namely – A.L.U (Arithmetic Logical Unit) and C.U (Control Unit). Both of these units work in sync with each other. The CPU processes the data as a whole.

Let us see what particular tasks are assigned to both units.

ALU – Arithmetic Logical Unit

The Arithmetic Logical Unit is made of two terms, arithmetic and logic. There are two major functions that this unit performs.

1.     Data is inserted through the input unit into the primary memory. Performs the basic arithmetical operation on it. Like addition, subtraction, multiplication, and division. It serves all sorts of calculations required on the data. Then sends back data to the storage.

2.     The unit is also responsible for performing logical operations like AND, OR, Equal to, Less than, etc.  In addition to this, it conducts merging, sorting, and selection of the given data.

CU –Control Unit

The control unit as the name suggests is the controller of all the activities/tasks and operations. All this is performed inside the computer.

The memory unit sends a set of instructions to the control unit. Then the control unit, in turn, converts those instructions. After that these instructions are converted to control signals.

These control signals help in prioritizing and scheduling activities. Thus, the control unit coordinates the tasks inside the computer in sync with the input and output units.

Memory Unit(M.U)

All the data that has to be processed or has been processed is stored in the memory unit. The memory unit acts as a hub of all the data. It transmits it to the required part of the computer whenever necessary.

The memory unit works in sync with the CPU. This helps in faster accessing and processing of the data. Thus, making tasks easier and faster.

There are two types of computer memory-

1.Primary memory

This type of memory cannot store a vast amount of data. Therefore, it is only used to store recent data.

The data stored in this is temporary. It can get erased once the power is switched off. Therefore, is also

called temporary memory or the main memory.

RAM stands for Random Access Memory. It is an example of primary memory. This memory is directly

accessible by the CPU. It is used for reading and writing purposes. For data to be processed, it has to be

first transferred to the RAM and then to the CPU.

2.Secondary memory

As explained above, the primary memory stores temporary data. Thus it cannot be accessed in the future. For permanent storage purposes, secondary memory is used. It is also called the permanent memory or the auxiliary memory. The hard disk is an example of secondary memory. Even in a power failure data does not get erased easily.

For details about the memory, please click here


There is nothing to be amazed by what the output unit is used for. All the information sent to the computer once processed is received by the user through the output unit. Devices like printers, monitors, projectors, etc. all come under the output unit.

The output unit displays the data either in the form of a soft copy or hard copy. The printer is for the hard copy. The monitor is for the display. The output unit accepts the data in binary form from the computer. It then converts it into a readable form for the user. 


Let us finally look at what the data flow looks like inside the computer step by step-

1.     The data is accepted by the input unit which is given by the user and then converted into binary form for the computer to read it.

2.     The information is then sent to the memory unit for storage and processing. 

3.     The required data that needs to be processed is accessed by the CPU. It is accessed from the primary storage. The arithmetic and logical operations are then performed on the data. The control unit schedules all the activities for the smooth working of the computer. 

4.     The data is then sent to the storage unit. It is used for storing or further processing purposes. 

5.     Then the output unit receives the final processed output.

With this, we have come to the end of this tutorial on the block diagram of a computer and its components. I hope this will help you with your understanding of computers.

If you have any questions in mind, please feel free to ask me in the comment section or you can contact me via email.

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