Computer Awareness — SSC CGL General Awareness Notes

History and generations

Charles Babbage is called the father of the computer (Difference Engine, Analytical Engine); Ada Lovelace is regarded as the first programmer.

ENIAC (1946, USA) was the first general-purpose electronic digital computer.

Generations: 1st – vacuum tubes; 2nd – transistors; 3rd – integrated circuits (ICs); 4th – microprocessors (VLSI); 5th – artificial intelligence (ULSI, parallel processing).

India's first supercomputer: PARAM 8000 (1991) by C-DAC, Pune, led by Vijay Bhatkar.

Parts of a computer

CPU (the 'brain') has the ALU (arithmetic and logic operations), the Control Unit (directs all operations) and registers (fastest, smallest storage).

Processor speed is measured in hertz (GHz); the motherboard connects all components; SMPS supplies power.

Input devices: keyboard, mouse (invented by Douglas Engelbart), scanner, microphone, MICR (cheques), OCR (printed text), OMR (answer sheets), barcode reader, light pen, joystick.

Output devices: monitor, printer (impact: dot-matrix; non-impact: laser, inkjet), plotter, speaker. A touchscreen works as both input and output.

On start-up, the BIOS (stored in ROM) runs the POST (power-on self-test) and loads the operating system: this is called booting.

Memory

Primary memory: RAM (volatile, loses data when power is off; SRAM is used for cache, DRAM for main memory) and ROM (non-volatile; PROM, EPROM erased by UV light, EEPROM erased electrically).

Cache memory sits between the CPU and RAM and holds frequently used data.

Secondary storage: hard disk (HDD), solid-state drive (SSD), pen drive (flash memory), CD (about 700 MB), DVD (4.7 GB single layer), Blu-ray (25 GB single layer).

Speed order (fastest first): registers > cache > RAM > SSD > HDD.

Practice

SSC-style: Which memory is volatile? Answer: RAM.

SSC-style: 1 nibble equals how many bits? Answer: 4.

Types of software

System software: operating system, device drivers, utilities (antivirus, disk cleanup). Application software: word processors, spreadsheets, browsers, games.

Open-source software (e.g. Linux, LibreOffice) has freely available source code; proprietary software (e.g. Windows, MS Office) does not. Freeware is free to use; shareware is free for a trial period.

Languages: machine language (binary, 1st generation), assembly language (mnemonics, 2nd), high-level languages such as C, Java, Python (3rd).

Translators: compiler (translates the whole program at once), interpreter (line by line), assembler (assembly to machine code).

Operating systems

The OS is the interface between user and hardware; it manages processes, memory, files and devices.

Examples: Windows (Microsoft), macOS and iOS (Apple), Linux (kernel by Linus Torvalds, 1991, open source), Android (Google, Linux-based), Unix (Bell Labs, 1969), MS-DOS (command-line).

A GUI uses icons and windows; a CLI uses typed commands. Multitasking runs several programs at once.

Device drivers let the OS communicate with hardware such as printers; a cold boot starts a computer from power-off, a warm boot restarts it.

Files are organised in folders (directories); deleted files go to the Recycle Bin in Windows until it is emptied.

MS Office essentials

MS Word – word processing (.docx); mail merge creates personalised letters from a data list.

MS Excel – spreadsheet (.xlsx); a cell is the meeting point of a row (number) and column (letter), e.g. B3; every formula starts with '='; common functions SUM, AVERAGE, MAX, MIN, COUNT, IF, VLOOKUP. A worksheet has 1,048,576 rows and 16,384 columns (last column XFD).

MS PowerPoint – presentations (.pptx); F5 starts the slide show. MS Access – database (.accdb). MS Outlook – e-mail and calendar.

Practice

SSC-style: Which shortcut is used to undo the last action? Answer: Ctrl + Z.

SSC-style: A program that translates the whole source code at once is a? Answer: Compiler.

Origin of the internet and the Web

ARPANET (1969), funded by the US Department of Defense, was the forerunner of the internet; it adopted TCP/IP on 1 January 1983.

The World Wide Web was invented by Tim Berners-Lee at CERN in 1989; it uses HTML pages linked by URLs and HTTP. The internet is the network; the Web is a service on it.

Public internet in India was launched by VSNL on 15 August 1995. 5G services were launched in India on 1 October 2022.

Networks and devices

Types by area: PAN (personal, e.g. Bluetooth), LAN (a building), MAN (a city), WAN (country or world; the internet is the largest WAN).

Topologies: bus, star (central hub or switch), ring, mesh (every node linked to others; most reliable), tree, hybrid.

Modem (modulator–demodulator) converts digital signals to analog and back; a router forwards data between networks; a switch connects devices in a LAN; a repeater boosts signals; a gateway joins networks with different protocols.

Addresses: IPv4 is 32-bit, IPv6 is 128-bit; a MAC address (48-bit) identifies a network card. DNS converts domain names into IP addresses.

The OSI model has 7 layers: physical, data link, network, transport, session, presentation, application.

E-mail and web terms

Ray Tomlinson sent the first network e-mail (1971) and chose the '@' symbol. SMTP sends mail; POP3 and IMAP receive it.

CC sends a visible copy; BCC sends a hidden copy; unwanted bulk mail is spam.

A browser (Chrome, Firefox, Edge) displays web pages; a search engine (Google, Bing) finds them. Cookies are small files a website stores on your browser.

Cloud computing models: SaaS (software, e.g. Gmail), PaaS (platform), IaaS (infrastructure).

Practice

SSC-style: Who invented the World Wide Web? Answer: Tim Berners-Lee.

SSC-style: Which protocol is used to send e-mail? Answer: SMTP.

Malware

Virus: attaches to a file or program and spreads when it is run; needs a host.

Worm: copies itself across networks without a host or user action.

Trojan horse: looks like useful software but opens a backdoor; it does not self-replicate.

Ransomware encrypts files and demands payment (e.g. WannaCry, 2017); spyware secretly collects information; keyloggers record keystrokes; a botnet is a network of infected computers controlled remotely.

'Brain' (1986), written in Lahore, is considered the first virus for IBM PCs.

Common attacks and frauds

Phishing (fake e-mails or websites), vishing (voice calls), smishing (SMS) trick people into revealing passwords, OTPs or card details.

DoS/DDoS floods a server with traffic so it cannot serve users; man-in-the-middle intercepts communication; SQL injection attacks databases through input fields.

Identity theft and SIM-swap fraud misuse personal data to take over accounts.

Protection

Use a firewall (filters network traffic), updated antivirus, strong unique passwords and two-factor authentication.

Check for HTTPS and the padlock icon before entering data; never share OTPs; keep software updated and back up data.

Encryption turns readable data into coded form that only an authorised key can unlock.

Laws and agencies in India

Information Technology Act, 2000: Section 66 (computer offences), 66C (identity theft), 66D (cheating by personation), 66F (cyber terrorism). Section 66A was struck down in Shreya Singhal v. Union of India (2015).

CERT-In (under MeitY) is the national nodal agency for cyber incident response; I4C (Indian Cyber Crime Coordination Centre, under MHA) coordinates action on cyber crime.

Report cyber fraud on helpline 1930 or at cybercrime.gov.in. The Digital Personal Data Protection Act, 2023 governs the processing of personal data.

Practice

SSC-style: Malware that spreads through networks without a host program is a? Answer: Worm.