Block Diagram Of Computer

The computer is the only technology in all over the world which is most widely used by people in various fields like education, for scientific applications, business, in industries, etc. The word computer has been derived from the word “compute” which means to calculate. Hence, it is a technology used to perform arithmetic operations at extremely very high speed with more accuracy as compared to the calculations done manually by humans. The computer has become more & more advanced as technology is growing very fast within the time. The word processor transforms the raw data into a piece of useful information.

Block Diagram Of Computer

The other words used for the computer are a word processor, data processor, workstation, electronic brain, personal computer, minicomputer, microcomputer, calculator, laptop computer, etc. It includes:

  • the user gives input & it is accepted by the computer.
  • stores the data.
  • process the required data.
  • gives output to the user.
  • have control inside the computer over its functions.


The devices that are used to give input to the data processor are keyboard, scanner, joystick, mouse, etc. and the process includes CPU to process the data while monitor and printer are common devices to give output to the user.

A computer is the composition of the following functional units:

  • Input Unit
  • Memory / Storage Unit
  • CPU (Central Processing Unit)
  • Output Unit

Secondary Storage<…….>Primary Storage<…….Control Unit…….>A.L.U

A.L.U is the abbreviation of Arithmetic & Logic Unit

Let’s discuss all the components of the computer:


As we all know that computers can’t think on their own & they need a set of instructions by the user to process the data. In simple words, you can say that it is an electronic brain that processes data as stated in the instructions given to it by the users and then, it yields the results. The input unit is used to feed information and stored this fed information in the computer’s memory for processing. The input devices used for providing information or instructions to the computer are keyboard, mouse, joystick, scanner, etc. These input devices are the bridge between the external world and the computer memory as they execute information from the exterior world to the system and then, process this information to produce results through output unit like monitor, printer, etc. The following functions performed by the input devices are :

  •  receive the data or instructions from the user.
  • convert the received data into machine form language.
  • supplies the data to the computer system for further processing.
  • after processing the data & instructions system produces results and receives using output devices such as monitor, printer.


It is an important element of the computer used to store data, instructions and final results in the system so that the data can be delivered or access to the user whenever they need or required to access it.

At first, instructions are accepted by the input unit & after that, it supplies the data to the computer system for further processing. Memory or storage unit is used to hold the instructions to first execute them and then, process them. In other words, you can say that the storage unit is a space where you can store processed data or processed results.

Types of Computer Storage are:


Cache<………………….>RAM (Primary Storage)

Cache<………………….>Hard drive (Secondary Storage)

Cache<………………….>CD-RW, USB thumb drive, Tape drive (Off-line Storage)

(a) Primary Storage Unit: The memory that directly communicates with the processor (CPU) is called Primary memory. The instructions or data read by the input unit are stored in the primary storage before processing and next transferred this data to the ALU (Arithmetic & Logic Unit) for the next step of further processing. It is also called temporary memory, main memory, internal memory. Temporary memory is named so because it stores data temporarily, data can be lost due to any power failure and is unable to store large amounts of data. It is also called volatile memory as it holds or keeps the data till the voltage or electric power is supplied to it otherwise you will lose your data and instructions if there is no continuous electrical charge.

Primary Memory communicates directly with the processor:

Primary memory<…………………..Processor

Examples of Primary Storage or Main/Volatile Memory:

  • RAM (Random Access Memory): It is also called immediate access store (IMAS). It is a group of chips located in the motherboard of the computer system, it is a type of primary storage as it stores data temporarily. There are two types of RAM: SRAM & DRAM.
  • Cache Memory: Cache is also called volatile memory. It is quite small in size and very fast in speed. It lies between the RAM & the processor in the form of CPU Register.
  • ROM (Read Only Memory): It is a non-volatile memory. It retains the data without the flow of electricity. It stores data permanently & does not losses data when power is not supplied. There are three types of ROM: PROM, EPROM, EEROM.

(b) Secondary Memory: Secondary Memory stores data and instructions permanently or for a long-term. Data stored in ROM never lost due to the power failure. It means it retains the data without supply of any power that’s why it is known as non-volatile memory. Hence, the user can approach the data stored in ROM anytime whenever it is required. It indirectly communicates with the processor.

Examples of Secondary/Non-Volatile Memory:

  • Hard Disk: Hard disk is a storage which can be used internal as well as external. It stores your data or files permanently so, that you can access them whenever you want.
  • Floppy Disk: Floppy disk is large and have less storage capacity. Floppy disk is composed of rings. These rings are called track and the track is further divided into sectors. Data is stored into this track
  • Compact Disk (CD): It is a storage device used to store and record different types of data in digital form like video, playback audio, etc.
  • Magnetic Tape: Magnetic tapes are used to store data, they are used in the form of cassettes & cartridges. Cassettes are used to store audio while cartridges are used to store different kinds of data like audio, video, etc.


CPU is also known as the brain of the computer as the processing of the programs is done on this unit. The data enters through any input device is called raw figures/facts. Suppose you have entered the data by using any input device, after entering this data goes to the processing unit & after that, this processing unit (CPU) understands the input data and then, converts it into information that could be easily understood by the users. The information results in output is called useful or meaningful information.

This unit has control over the functions/working of all the parts of the computer. Microprocessor is used in CPU’s that works like the integrated circuit (IC).

Instruction Cycle:

(1) Get The Instruction
(2) Figure The Instruction
(3) Determine/Measure The Effective Address
(4) Execute The Instruction


Elements Of CPU

  • Registers: Registers are the memory locations present in the processor or you can say that electronic storage devices that can store/hold & transfer data at extremely high speed. They store the information as bits. These registers are used during processing the different types of operations. These storage devices are the fastest temporary storage location as they exist inside the microprocessor so it becomes more easy for the CPU to access the data. The more the number of the registers available in a processor the better will be the performance of the CPU or they improve the action/work of the CPU. A register is a collection of many flip-flops and flip-flop means a single cell which is capable to store a single bit. The register available in a processor is made up of groups of small cells & a cell can store a particular bit. For example: if a register is about 4 bit that means it has four cells or four flip-flops.
  • Control Unit: Control unit serves as a supervisor as it understand which operation to execute in which order. It is the most important element of the computer which controls the overall functioning of the CPU or you can say that it directs all operations performed on the computer system. The control unit gets the instructions from the decodes/interprets the instructions and then sends the central processor for further processing.
  • Arithmetic & Logic Unit: It is the digital circuit of the CPU that is used to perform arithmetic operation as well as logical operations in the computer. Arithmetic calculations include addition, subtraction, multiplication & division while logical calculations include comparisons or decisions like comparing two numbers and then, check they are equal, greater or less. Instructions stored in the primary memory are transferred to the ALU for processing, then sends results/output to the main memory. The processing is done in the ALU, not in the primary memory. It also called the core of the CPU because that is ALU which executes or processes the data so more the numbers of ALU present in a processor the faster the speed of the CPU.


    The output unit is used to generate and provide the final result to the user. This result is displayed on the output medium such as monitor, printer, etc. The output unit accepts/ receives the instructions in the binary code, converts these binary codes into human-readable form and after that produces the converted result to the user.

    Examples of the Output unit:

    • Monitor
    • Printer
    • Plotter
    • Speakers, etc.

      SRAM Vs DRAM/Types of RAM

      It stands for Static Random Access Memory It stands for Dynamic Random Access Memory
      More fast as compared to the dram It is a slow process
      It includes transistors to store a single bit of data Includes separate capacitors to store each bit of data
      Does not require periodically refreshment to maintain data Requires periodically refreshment
      Used in cache memory Used in main memory
      Expensive Inexpensive
      Use less power Use high power
      Made up of flip-flop Made up of capacitors
      Low storage capacity High storage capacity
      Small Large


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