Block Diagram of a Computer4 min read

Computer Block Diagram: Block diagram of computer displays the structural or pictorial representation of a computer system. In other words, a block diagram of the computer will let you visualize how the computer works starting from inputting the data to retrieving the output.

The following is the block diagram of computer system.

Block Diagram of Computer

The Computer System works with the combination of the following three components.

  • Input Unit
  • Central Processing Unit
    • ALU – Arithmetic Logic Unit
    • CU – Control Unit
  • Memory Unit
    • Primary memory
    • Secondary memory
  • Output Unit

Explain block diagram of a computer

Input Unit

The input units are the input devices attached to a system through which the users enter the instruction for the computer to perform. These devices are the mouse, keyboard, scanner, etc. We can say that these devices are the means of communication between the user and the system.

The computer takes the input as the raw data that is the binary (machine-readable form) and performs the further processing. Later, when the processing is complete, it gives the output in output devices such as through monitors, printers, etc.

Central Processing Unit (CPU)

The CPU is the brain/heart of the computer. The computer is nothing without the CPU. All the instruction that is given by the user to the computer is processed by the CPU. The CPU gets the input from the user or the set of instructions and produces the output accordingly.

It is an electronic hardware device that performs all the operations such as arithmetic and logical operations. It is responsible for activation and controlling the operation of other units.

Block diagram of CPU:

block diagram of CPU

It consists of two major components and they are:

  • Arithmetic and Logic Unit (ALU)
  • Control Unit (CU)

Arithmetic and Logic Unit (ALU):

In this part of the CPU, all the arithmetical and logical operations are performed.

The arithmetic operations such as addition, subtraction, multiplication, and division are performed in the arithmetic section, and the logical operation such as AND, OR, Equal, Less than, Greate than, etc are performed on the logical section. Logical is also responsible for comparing, matching, selecting, etc operations.

Control Unit (CU):

From the name itself, we can conclude that the control unit (CU) controls all the activities or operations which are performed inside the computer system.

As you can see in the diagram above the control unit is connected to the memory unit of the system that means it receives instructions or information directly from the main memory of the computer. The control unit converts those instructions into a set of signals and then transmits those signals to the other part of the computer system for further processing.

Memory Unit

The memory unit is one of the major components of a computer system or component of a digital computer that is also called a storage unit. The data and instructions are stored in a memory unit for further after and before processing. The intermediate and final results are stored in this unit.

The instructions are transmitted to different parts of the system from the memory unit. There are two types of memory units and they are:

Primary Storage Unit:

The primary memory stores the temporary data or instruction. They cannot store a huge amount of data. It is used to store the instruction that is currently being performed or the immediate calculation result. Once the power to the computer is cut off, the data in this primary will be lost.

It is also known as the Main memory or the Temporary memory. One example of this type of memory is RAM(Random Access Memory).

Secondary Storage Unit:

When we need to store the data permanently for future processing then we use the secondary memory of the computer. It is exactly the opposite of primary memory. The data is not lost even if the power supply fails.

It is also called secondary or auxiliary storage or permanent storage. One example of this type of memory is a Hard Disk or an SSD (Solid-state drive).

Note: The CPU can directly access the primary memory but the secondary memory is not accessible to the CPU directly. The data from the secondary memory is first loaded to the RAM (primary memory) and then the CPU can access it.

Output Unit

The output units are the output devices attached to a system through which the users can see the result of the inputted data. These devices are printers, monitors, etc.

The data is first stored in the memory and then converted to human-readable form from binary code and then displayed on the output devices.

The output unit provides the result into two forms such as soft copy or hard copy. The monitor is used for a soft copy as it displays on the screen, whereas the printer is used for hard copy as it prints the output on the paper.


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