Computers, IT & Internet Awareness Notes for SSC, IB, IBPS, SBI, RRBs 2019

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Computer (Hardware + Software)

A computer performs a specified sequence of operations as per the set of instructions (known as programs) given on a set of data (input) to generate desired information (output).


Input Devices Processing Devices Output Devices Storage Devices
Keyboard Motherboard Monitor (LED, LCD, CRT) Magnetic Disk
Microphone Processor Printer Optical Disk
Mouse CPU Speaker Flash Memory
Web Camera GPU Plotter Magnetic Tape
Touch Screen Network card Projector
Light Pen Sound card
Joystick Video card


System Software Application Software
Operating Systems Text Editors
Device Drivers Internet browsers
Middleware Graphics Editors
Utility software Multimedia Players

Operating System

Single User Multi User
Windows 95 Ubuntu
MS-Dos macOS
Windows NT Workstation All linux based OS
Windows 2000 professional IBM AS400
Windows 10 Unix


1. ALU (Arithmetic Logic Unit)

Performs all arithmetic and logical operations.

2. Registers

All data must be represented in a register before it can be processed. The register can contain the address of a memory location where data is stored rather than the actual data itself.

3. CU (Control Unit)

It controls various operations of different parts of Computer.

Data vs Information

Data are simply facts or figures — bits of information, but not information itself. When data are processed, interpreted, organized, structured or presented so as to make them meaningful or useful, they are called information. Information provides context for data.

Data Processing Cycle: Input -> Processing -> Output

Language Processors

  • Assembler: Used to convert assembly language code into machine code.
  • Compilers: Used to convert high level languages (C, C++) into machine code.
  • Interpreter: Directly executes instructions line by line written in a programming language, (without the need of compiling into a machine language).

Memory Storage Units

Unit Description
Bit (Binary Digit) Either logical 0 or 1
Nibble 1 nibble = 4 bits
Byte 1 Byte = 8 bits
Kilobyte (KB) 1 KB = 1024 Bytes
Megabyte (MB) 1 MB = 1024 KB
Gigabyte (GB) 1 GB = 1024 MB
Terabyte (TB) 1 TB = 1024 GB
Petabyte (PB) 1 PB = 1024 TB
Exabyte (EB) 1 EB = 1024 PB
Zettabyte (ZB) 1 ZB = 1024 EB
Yottabyte (YB) 1 YB = 1024 ZB

Generations of Computers

  • 1st Generation (1946-59): vacuum tube based
  • 2nd Generation (1959-65): transistor based
  • 3rd Generation (1965-71): IC based
  • 4th Generation (1971-80): microprocessors, VLSI based
  • 5th Generation (1980 onward): ULSI, AI based

Important Creators/Inventors

Creation Scientist
Java James Gosling (Sun Microsystems)
C Dennis Ritchie
C++ Bjarne Stroustrup
Python Guido van Rossum
PHP Rasmus Lerdorf
JavaScript Brendan Eich
WWW TimBL (Tim Berners-Lee)
Mechanical Computer Charles Babbage
Computer Mouse Douglas Engelbart
Computer/Modern Computer Charles Babbage
Internet Tim Berners-Lee (TimBL)
Email Raymond Samuel Tomlinson
Laser Printer Gary Starkweather
Bluetooth Dr. Jaap Haartsen (Ericsson)

Booting (Cold Boot, Warm Boot)

Process of starting up a computer until it can be used.

  • Cold Boot: When Computer is turned ON from an OFF position.
  • Warm Boot: When Computer is reset (i.e., turned OFF from ON position and then turned ON), by pressing power button.

OSI (Open Systems Interconnection) Model

It’s a 7 layer conceptual model that characterizes and standardizes the communication functions of a telecommunication or computing system without regard to its underlying internal structure and technology.

  1. Application Layer
  2. Presentation Layer
  3. Session
  4. Transport
  5. Network
  6. Data Link
  7. Physical

Trick to remember the 7 layers: “All people seem to need data processing.” or Aaj Pappu SAB TV nahi dekh paya”


A supercomputer is a computer with a high level of performance compared to a general-purpose computer.

  • India’s First Supercomputer: PARAM 8000 by C-DAC, Pune
  • World’s First Supercomputer: Cray CDC 6600, by Control Data Corporation, US
  • India’s Fastest Supercomputer: Pratyush or Cray XC40 by Indian Institute of Tropical Meteorology, Pune (CAP 6.8 petaflops)
  • World’s Fastest Supercomputer: Summit or OLCF-4 by IBM, US (CAP 200 petaflops)

Logic Gates

There are seven basic logic gates: AND, OR, XOR, NOT, NAND (AND + NOT), NOR (OR + NOT), and XNOR (XOR + NOT).

Combinational Circuits

1. Adder (Half, Full)

  • Half Adder: adds 2 single bits and produces 1 output.
  • Full Adder: adds 3 single bits and produces sum and carry as outputs.

2. Multiplexer (2×1 mux, 4×1 mux, 16×1 mux, 32×1 mux, etc.)

Multiple inputs and 1 output.

3. Demultiplexer (1×2 demux, 1×4 demux, 1×16 demux, 1×32 demux)

Performs the reverse operation of a multiplexer i.e. it receives 1 input and distributes it over several outputs.

4. Decoder (Code Converters, BCD to 7 Segment, Relay actuator)

Has n input lines and maximum of 2n output lines.

5. Encoder (Priority, Decimal to BCD, Octal to binary, Hexadecimal to binary)

Performs the inverse operation of the decoder.


An intranet is a private network belonging to an organization.


It is a global system of interconnected computer networks.

  • It uses the standard Internet Protocol (TCP/IP).
  • Every computer in Internet is identified by a unique IP address.
  • IP Address: is a (32 bit in IPv4 and 128 bit in IPv6) unique set of numbers (such as which identifies a computer’s location.
  • World Wide Web: a network of web pages formatted in markup languages (HTML, XML, etc.) and accessed via HTTP
  • The World Wide Web was originally designed in 1991 by Tim Berners-Lee (popularly known as Father of WWW) while he was a contractor at CERN.

Networking (LAN, MAN, WAN)

  • LAN (local area network) is a group of computers and network devices connected together, usually within the same building.
  • MAN (metropolitan area network) is a larger network that usually spans several buildings in the same city or town.
  • WAN (wide area network) is generally confined within the bounds of a state or country.

Network Protocols

1. Internet Protocols (IP)

1.1 TCP (Transmission Control Protocol)

Transmission Control Protocol is one of the most used protocols in digital network communications and is part of the Internet protocol suite, commonly known as the TCP/IP suite. Primarily, TCP ensures end-to-end delivery of data between distinct nodes.

UDP (User Datagram Protocol)

1.2 UDP is an alternative communications protocol to Transmission Control Protocol (TCP) used primarily for establishing low-latency and loss-tolerating connections between applications on the internet.

HTTP(HyperText Transfer Protocol)

1.3 HTTP is the underlying protocol used by the World Wide Web and this protocol defines how messages are formatted and transmitted, and what actions Web servers and browsers should take in response to various commands.

FTP (File Transfer Protocol)

1.4 FTP is a standard network protocol used for the transfer of computer files between a client and server on a computer network.

2. Wireless Network Protocols

2.1 WiFi (Wireless Fidelity)

WiFi is a technology for radio wireless local area networking of devices based on the IEEE 802.11 standards.

2.2 Bluetooth

Bluetooth is a wireless technology standard for exchanging data over short distances (using short-wavelength UHF radio waves in the ISM band from 2.4 to 2.485 GHz) from fixed and mobile devices, and building personal area networks (PANs).

2.3 LTE (Long Term Evolution)

In telecommunication, Long-Term Evolution (LTE) is a standard for high-speed wireless communication for mobile devices and data terminals, based on the GSM/EDGE and UMTS/HSPA technologies.

Web Browser

A web browser (commonly referred to as a browser) is a software application for retrieving, presenting and traversing information resources on the World Wide Web.

Examples: Internet Explorer, Google Chrome, Safari, Opera, etc.

VIRUS (Vital Information Resources Under Seize)

A computer virus is a type of malicious software that, when executed, replicates itself by modifying other computer programs and inserting its own code.


A firewall is a network security system that monitors and controls the incoming and outgoing network traffic based on predetermined security rules. A firewall typically establishes a barrier between a trusted, secure internal network and another outside network.


Spyware is unwanted software that infiltrates your computing device, stealing your internet usage data and sensitive information.


A computer worm is a standalone malware computer program that replicates itself in order to spread to other computers.

Trojan Horses

Trojan Horses is any malicious computer program (appears harmless) which misleads users of its true intent.

Data Link Layer

The data link layer resides above the Physical Layer and below the Network Layer. The logical Link Control sublayer is responsible for synchronising frames, error checking, and flow control.

Classification of Computer Memory

Classification of Computer Memory

VSAT (Very Small Aperture Terminal)

VSAT is a two-way satellite ground station or a stabilised maritime VSAT antenna with a dish antenna that is smaller than 3 meters.

First Programming language: FORTRAN (derived from Formula Translation)
Example of word processors/Text Editor: In windows WordPad, Notepad, MS Word, etc., In Mac TeachText, SimpleText
Example of spreadsheets: MS Excel, iWork Numbers, etc.
Example of Presentation maker: MS PowerPoint, Keynote, etc

Primary Key

A Primary Key in a relational database is unique for each record. It is a unique identifier, such as a driver licence , telephone number, etc.

Note: A relational database must always have one and only one primary key.

Instruction Cycle

An Instruction cycle is the basic operation cycle of a computer. It is the process by which a computer retrieves a program instruction from its memory, determines what actions the instruction requires and carries out those actions.


The synchronous transfer can be implemented with a method called handshaking. This method is used to accompany each data item being transferred with a control signal that indicates the presence of the presence of data in the bus. The unit receiving the data item responds with another control signal to acknowledge receipt of the data.

RAM (Random Access Memory) (Volatile Memory)

RAM is a form of computer data storage. A RAM device allows data items to be accessed (read or written) in almost the same amount of time irrespective of the physical location of data inside the memory.

Control Store

The control store Contains the set of micro-instructions that are used to execute all of the programs run that computer. The control store is referenced by the MPC, the micro-program counter, a device similar to a register.

Note: The MPC stores the location of the micro-instruction that is currently being executed.

Most Important Full Forms

Abbreviation Full Form Abbreviation Full Form
CAD Computer Aided Design HHDD Hybrid Hard Disk Drives
JPEG Joint Photographic Experts Group MICR Magnetic Ink Character Recognition
PNG Portable Network Graphics ISDN Integrated Services Digital Network
GIF Graphics Interchange Format UPS Uninterrupted Power Supply
DNS Domain Name System VOLTE Voice Over LTE
VIRUS Vital Information Resources Under Seize HTTP Hyper Text Transfer protocol
HTML Hypertext Markup Language LED Light Emitting Diode
ASCII American Standard Code for Information Interchange

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