NIOS Computer Science Chapter 1 – Anatomy of a Digital Computer Part 1

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Anatomy of a digital computer part

Anatomy of a Digital Computer Part

Anatomy of a digital computer part

A device that accepts data, processes the data in accordance with a stored program, generates results, and usually consists of input, output, storage, and arithmetic, logic, and control units.


(i) Central Processing Unit (CPU): The ‘brain’ of the computer, the component that actually executes instructions. Convert it into electrical signals and transmit it to the processor.

(ii) Memory: It enables a computer to store, at least temporarily, data and programs.

(iii) Input device: Usually a keyboard or mouse is used to read data and programs into the computer.

(iv) Output device: A display screen, printer, etc. that lets you see what the computer has accomplished.

(v) Mass storage device: It allows a computer to permanently store large amounts of data. Common mass storage devices include disk drive and tape drive.

Functions and Components of a computer

Functions and Components of a computer Images

Functions and Components

Functions and Components of a computer Images

1. Central processing Unit (CPU):- A computer's CPU handles all instructions it receives from hardware and software running on the computer.

2. Control Unit (CU):- A control unit or CU is circuitry that directs operations within a computer's processor. It lets the computer's logic unit, memory, as well as both input and output devices know how to respond to instructions received from a program

3. Arithmetic- Logic unit:-The ALU is a complex digital circuit. It performs both bitwise and mathematical operations on binary numbers and is the last component to perform calculations in the processor.

4. Memory:-Computer memory is any physical device capable of storing information temporarily or permanently. For example: Random Access Memory (RAM).

5. Registers:- Register are used to quickly accept, store, and transfer data and instructions that are being used immediately by the CPU, there are various types of Registers those are used for various purpose.

Types of Registers are as Followings

1. Program Counter: A program counter is a register in a computer processor that contains the address (location) of the instruction being executed at the current time.

2. Accumulator Register: In a computer's central processing unit (CPU), an accumulator is a register in which intermediate arithmetic and logic results are stored.

3. Memory Data Register (MDR): The Memory Data Register (MDR) contains the data value being fetched or stored.

4. Index Register: An index register is a circuit that receives, stores, and outputs instruction-changing codes in a computer. This circuit is also called an address register or a register of modifications.

5. Memory Buffer Register: A memory buffer register (MBR) is the register in a computer's processor, or central processing unit, CPU, that stores the data being transferred to and from the immediate access store. It contains the copy of designated memory locations specified by the memory address register.

6. Data Register: The Memory Data Register (MDR) or Memory Buffer Register (MBR) is the register of a computer's control unit that contains the data to be stored in the computer storage (e.g. RAM), or the data after a fetch from the computer storage.

Input Devices

Input Devices Image

Input Devices Image

Input Devices Image

Optical Character Recognition

  • OCR (optical character recognition) is the recognition of printed or written text characters by a computer.

  • Involves photo scanning of the text character-by-character.

  • Analysis of the scanned-in image, and then translation of the character image into character codes, such as ASCII, commonly used in data processing.

Magnetic lnk character Recognition (MICK)

MICR (magnetic ink character recognition) is a technology used to verify the legitimacy or originality of paper documents, especially checks.

Bar Code Reader

These devices are generally available in super markets, bookshops, etc.

Bar-code readers are photoelectric scanners that read the bar codes or vertical zebra striped marks, printed on product containers.

Digitiging Tablet

This is an input device that enables you to enter drawings and sketches into a computer.


Scanner is an input device that can read text or illustrations printed on paper and translate the information into a form that the computer can use.


Mouse is a device that controls the movement of the cursor or pointer on a display screen. It is a small object you can roll along a hard and flat surface.

Light Pen

Light pen is an input device that utilizes a light-sensitive detector to select objects on a display screen.

Speech input devices

Speech or voice input devices convert a person's speech into digital form.

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