Block diagram of computer | Parts of Computer

Parts of computer

Computer is a multipurpose machine. It reads binary instructions from the memory, executes them according to their instructions and provides the result. The instruction received from the memory is called ‘INPUT’ of the computer. Data processing and the result, which is done by the computer according to the instructions, is called ‘OUTPUT’ of the computer. Before the block diagram of the computer, let’s understand about the parts of the computer with the help of a photo. Below is a photo of parts of a computer, in which parts of computer are shown. Click here to read this article in Hindi

block diagram of computer

Block Diagram of Computer

The block diagram of a computer is shown in the figure. There are four main parts of a computer-

block diagram of computer

  • (i) Input
  • (ii) Central Processing Unit (CPU)
  • (iii) Memory
  • (iv) Output

(i) Input

Input devices are used to feed (enter) data into the computer. Every computer has a key board arrangement by which instructions or data can be typed like a normal typewriter.

Can The computer reads these instructions and processes the data according to the instructions • Apart from the key board, there are other methods of giving input to the computer. Such as A/D converter, text scanning, graphic input, light pens, touch screens, mouse, floppy etc.

At present, voice input devices have also been developed for input, through which sound can be converted into such a signal that the computer can understand.

(II) CPU (Central Processing Unit)

CPU is the heart of the computer. The block diagram of a CPU is given in the figure. It receives instructions from the memory and processes the data accordingly. According to the instructions given in the program, the CPU transmits the result to the output device or stores it in the memory. The data flow between the memory and input/output devices in the computer is controlled by the CPU only.

All mathematical and logic operations are also performed by CPU. CPU controls all these operations and sequences them. CPU has the following main parts-

block diagram of CPU

  • 1. Arithmetic & Logic Unit or ALU
  • 2. Timing and Control Unit
  • 3. Accumulator and General Purpose Registers

(1) ALU (Arithmetic and Logic Unit)

This unit completes all the mathematical and logic operations in the computer. for example

  • (i) add/subtract
  • (ii) OR, NOT, AND, XOR etc. operations
  • (iii) Shifting numbers to the right or left by one bit (Shifting left or right by one bit)
  • (iv) Compare
  • (v) Addition of BCD numbers
  • (vi) Incrementing and decrementing registers

After data processing, the results are stored in registers or memory) or transferred to another output device as per instruction.

(2) Timing and Control Unit

The function of the control unit is to control all the operations and keep them in proper sequence during data processing. This unit provides the timing and control signals required to control all the operations of the microcomputer. In addition, this unit controls the data flow between the microprocessor and peripherals (such as monitor, printer, floppy, memory, etc.).

(3) Accumulator and General Purpose Registers(GPRs)

The Accumulator (ACC) is an important register in a microprocessor. It stores the results of all mathematical and logic operations. And stores all the data before and after being transferred to the input/output port.

During the execution of a program, data is temporarily stored in General Purpose Registers (GPRs).

(iii) Memory

Memory is a storage device. It stores information and data in binary form and makes the information available to the microprocessor when required. For the execution of the program, the microprocessor reads (READ) the data and information from the external memory and processes them in the ALU. The obtained results are stored in the computer memory for future use or sent to any output device (such as video display, printer, etc.).

Memory is like a page of a book, each line of which has space to write a fixed number of binary numbers. For example, a line can only have space for 8 binary digits. In fact each line is an 8 bit register which can store 8 binary digits. A sequence of many such registers is called memory.

For example, there are 210 registers in 1 K byte memory, which is a group of about 1024 registers) The programmer writes the necessary instruction and data in the memory and instructs the computer to complete the task according to the instruction.
Memory is divided into two parts-

  • (i) Read Only Memory (ROM) and
  • (ii) Read / Write Memory (R / W) which is often called Random Access Memory (RAM).)

Such programs are stored in ROM memory which do not require any change. Programs stored in ROM can only be read.

R/W memory stores programs and data input by the user. Programs stored in R/W memory can be easily read and changed.

(iv) Output

The computer transmits the results to the output devices. Output devices can store results, print them, display them on a video unit, or convert them into electrical signals to operate a device. The main output devices are:

  • 1. CRT (Cathode Ray Tube)
  • 2. Printers
  • 3. LEDs (Light Emitting Diodes)
  • 4. D/A Converter
  • 5. Magnetic Tape etc.

Sometimes the output and input devices are combined to form a single unit that serves as both an input and an output. An I/O device consisting of a combination of a keyboard and a video unit (CRT) can communicate with a CPU placed elsewhere.

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