Computers are electronic machines that take input (data), process it, and give output (information). For SSC exams, computer questions are not about coding or deep tech — they're about definitions, memory types, networking terms, and security threats. Think of this note as 'Computer GK for someone who has never studied computers' — we'll explain everything from scratch.
1946
ENIAC — first electronic general-purpose computer (USA)
Weighed 30 tons; filled an entire room; no keyboard or screen
1951
UNIVAC I — first commercial computer sold in USA
1956
First hard disk drive by IBM (size of a refrigerator, stored 5 MB!)
1971
Intel 4004 — first commercial microprocessor chip
1975
Microsoft founded (Bill Gates + Paul Allen)
1976
Apple founded (Steve Jobs + Steve Wozniak)
1981
IBM PC — personal computer becomes mainstream
1991
World Wide Web invented by Tim Berners-Lee (not same as Internet!)
1998
Google founded (Larry Page + Sergey Brin)
2007
iPhone launched — smartphone era begins
COMPUTER BASICS — HARDWARE & SOFTWARE
A computer has two fundamental parts: Hardware (physical components you can touch — keyboard, mouse, monitor, CPU box) and Software (programs and instructions that tell hardware what to do — Windows, MS Word, apps). The brain of a computer is the CPU (Central Processing Unit) — it processes all data. The CPU contains three units: ALU (does math and logic), Control Unit (coordinates everything), and Registers (tiny high-speed storage for data currently being processed). For any task you want to do, you use an Input device → data is Processed by CPU → result shown on an Output device.
Unit
Full Form
What It Does
Examples
Input Unit
—
Takes data/instructions from the user and feeds it to the CPU
Performs all mathematical calculations (+, -, ×, ÷) and logical comparisons (>, <, =)
Inside every processor — does the actual 'thinking'
CPU — CU
Control Unit
Directs and coordinates the activities of all other units; fetches, decodes, and executes instructions
The 'traffic controller' of the computer
CPU — Registers
—
Tiny, ultra-fast memory inside CPU that holds data being actively used right now
Program counter, accumulator, instruction register
Output Unit
—
Displays or delivers the processed result to the user
Monitor, Printer, Speaker, Projector, Plotter
MEMORY — RAM, ROM & STORAGE
Computer memory comes in two forms: Primary Memory (fast, directly accessible by CPU — small in size) and Secondary Memory (slow, large capacity — your hard disk, pen drive). Primary memory has two types: RAM (temporary, loses data when power goes off — like a whiteboard you erase every night) and ROM (permanent, keeps data even without power — pre-installed). Think of RAM as your desk workspace (stuff you're working on now) and ROM as factory instructions printed in a book.
Computer Memory Types
Computer Memory
Primary Memory (Internal)Fast + Small
RAM (Random Access Memory) — Volatile; erased when power off; temporary workspace
DRAM (Dynamic RAM) — Needs refreshing; cheaper; used in main memory
SRAM (Static RAM) — Faster, doesn't need refresh; used in cache memory
ROM (Read Only Memory) — Non-volatile; permanent; stores BIOS/firmware
PROM — Programmable ROM (write once)
EPROM — Erasable PROM (UV light erases)
EEPROM — Electrically Erasable PROM (can be rewritten electronically — like USB flash)
Secondary Memory (External Storage)Slow + Large
Hard Disk Drive (HDD) — Magnetic storage; large capacity; slow
Solid State Drive (SSD) — Flash memory; fast; no moving parts
Cache Memory — Ultra-fast between CPU and RAM; stores frequently used data for quick access
Registers — Inside CPU; fastest memory; holds data being processed right now
Virtual Memory — Uses hard disk space as extra RAM when RAM is full
NETWORKING — LAN, MAN, WAN & INTERNET
Computer networking is simply connecting two or more computers so they can share data. Your home Wi-Fi is a small network. The Internet is the world's largest network — connecting billions of computers globally. Networks are classified by their geographic size: LAN (your home/office), MAN (a city), WAN (countries/world). The Internet works on the TCP/IP protocol — a set of rules that all computers agree to follow for sending data.
Network Type
Full Form
Coverage Area
Example
LAN
Local Area Network
Single building or campus (up to ~1 km)
Office network, school lab, your home Wi-Fi
MAN
Metropolitan Area Network
A city or town (~10–100 km)
Cable TV network in a city, city-wide Wi-Fi
WAN
Wide Area Network
Countries or continents
Internet, bank ATM network across India
PAN
Personal Area Network
~10 metres (personal space)
Bluetooth devices — phone to earbuds
Internet
Interconnected Networks (global)
Worldwide
World Wide Web, email, streaming — runs on TCP/IP
Term
What It Means
Remember
IP Address
Unique numerical address of every device on a network (like a postal address)
IPv4: 192.168.1.1 format; IPv6: newer, longer format
DNS (Domain Name System)
Translates website names (google.com) to IP addresses
'Phone book of the Internet'
HTTP / HTTPS
Protocol for web pages; HTTPS = secure (encrypted) version
S in HTTPS = Secure; look for it in URLs when doing banking
FTP
File Transfer Protocol — for transferring files between computers
Used to upload files to web servers
WWW (World Wide Web)
System of web pages linked by hyperlinks on the Internet
Invented by Tim Berners-Lee, 1991 — NOT same as Internet!
URL
Uniform Resource Locator — the web address (e.g., https://yoloprep.com)
What you type in browser address bar
Browser
Software to access and display web pages
Chrome, Firefox, Edge, Safari
Modem
Modulator-Demodulator — converts digital signals to analog for telephone line transmission and back
The device that connects your computer to your ISP
SECURITY THREATS — VIRUSES, MALWARE & CYBERCRIME
As computers became central to life, criminals started attacking them. Computer security threats are programs or techniques that harm your system, steal data, or spy on you. SSC tests the definitions of these threats — especially the difference between a Virus, Worm, Trojan, Spyware, and Malware. The key distinction: a Virus attaches to files; a Worm spreads by itself without attaching; a Trojan pretends to be useful software but is secretly harmful.
Threat
What It Is
Key Characteristic
Virus
A malicious program that attaches itself to legitimate files and replicates when those files run
Needs a HOST file to spread — like a biological virus needs a cell
Worm
A self-contained malicious program that replicates itself across networks WITHOUT needing a host file
Spreads on its own — clogs networks, slows down computers
Trojan Horse (Trojan)
Malicious software disguised as a useful, legitimate program
Doesn't replicate — tricks user into installing it (like the Trojan horse from mythology)
Spyware
Software secretly installed on your computer to collect your personal information (passwords, browsing habits) and send it elsewhere
You don't know it's there — runs in background
Adware
Software that displays unwanted advertisements, often while collecting usage data
Annoying pop-ups; sometimes bundled with free software
Ransomware
Malware that encrypts your files and demands payment (ransom) to unlock them
WannaCry (2017) hit hospitals and companies worldwide
Spam
Unsolicited bulk messages sent to many users, usually by email
Most spam is advertising; some is phishing (tricking you into giving passwords)
Phishing
Fake websites or emails that impersonate legitimate services to steal your login credentials
Fake bank email asking you to 'verify account' = phishing
Malware
Umbrella term for all malicious software
Superset: includes virus, worm, trojan, spyware, ransomware, adware
COMPUTER TERMS GLOSSARY
SSC asks 'what is X called in computers?' type questions. This glossary covers the most tested computer terms — each with a plain-English explanation so you understand it, not just memorise it.
Term
Full Form (if any)
Plain-English Meaning
Operating System (OS)
OS
Master software that manages all hardware and software; runs first when you switch on — Windows, macOS, Linux, Android, iOS
Compiler
—
Translates your entire program (written in human-readable code) into machine code IN ONE GO before running
Interpreter
—
Translates program into machine code LINE BY LINE as it runs (slower but easier to debug) — Python uses interpreter
Assembler
—
Converts Assembly language (low-level human-readable) into binary machine code
Cache Memory
—
Ultra-fast temporary storage between CPU and RAM — stores frequently used instructions so CPU doesn't have to wait for RAM
Cloud Computing
—
Using computing resources (storage, software, processing) over the Internet instead of your own computer — Google Drive, Dropbox, Gmail
Firewall
—
Security barrier (hardware or software) that monitors and filters incoming/outgoing network traffic based on security rules
Encryption / Cryptography
—
Converting data into a coded form so only authorised people can read it — used in banking, WhatsApp messages
Bandwidth
—
The maximum amount of data that can be transmitted over a network connection per second — measured in Mbps or Gbps
Latency / Ping
—
Time delay between sending a request and receiving a response — low latency = fast response (important for gaming/video calls)
Database
DBMS
Organised collection of structured data — SQL is the standard language to query databases
Artificial Intelligence (AI)
AI
Computer systems that perform tasks that normally require human intelligence — image recognition, language understanding, chess playing
Machine Learning (ML)
ML
Subset of AI — systems that learn from data and improve without being explicitly programmed
Bluetooth
—
Short-range wireless technology (PAN) — connects devices within ~10 metres; used for earbuds, keyboards, file transfer
USB
Universal Serial Bus
Standard connector for connecting peripherals (pen drives, keyboards, mice, phones) to computers
SUPERCOMPUTERS — INDIA & WORLD
Supercomputers are the most powerful computers in the world — used for weather forecasting, nuclear simulations, drug discovery, and climate modelling. India has developed its own supercomputers through C-DAC (Centre for Development of Advanced Computing) under the PARAM series. The world's top supercomputers are measured in 'FLOPS' (Floating Point Operations Per Second) — a petaFLOP = one quadrillion operations per second.
Supercomputer
Year
Developed By
Note
Param Siddhi
2020
C-DAC
One of India's most powerful; ranks in top 100 globally
Param Shivay
2019
IIT-BHU + C-DAC
First supercomputer installed at an IIT
Pratyush
2017
IITM Pune
Used for weather forecasting and climate modelling
Param Yuva II
2013
C-DAC, Pune
Earlier generation PARAM supercomputer
Aaditya
2013
Indian Institute of Tropical Meteorology
For tropical weather prediction
SAGA-220
2011
ISRO
Used for spacecraft design and simulation
ANUPAM-Adhya
2010–11
BARC
For nuclear research at Bhabha Atomic Research Centre
World Supercomputer
Year
Country
Operating System
Fugaku
2021
Japan
Custom Linux — fastest for several years
IBM Summit
2018
USA
IBM-based — used for COVID-19 research
Sunway TaihuLight
2016
China
Linux — entirely Chinese-made chips
Tianhe-2
2013
China
Kylin Linux
Titan
2012
USA
Linux — at Oak Ridge National Laboratory
QUICK-FIRE: Computer Science
Question
Answer
CPU stands for?
Central Processing Unit
ALU stands for?
Arithmetic Logic Unit — performs math and logical operations
RAM stands for?
Random Access Memory — volatile (erased when power off)
ROM stands for?
Read Only Memory — non-volatile (data persists without power)
Which memory is volatile?
RAM
Which memory is non-volatile?
ROM
What is Cache memory?
Fast buffer memory between CPU and RAM — stores frequently used data
LAN stands for?
Local Area Network — covers a single building/campus
WAN stands for?
Wide Area Network — covers countries/continents
What is the Internet?
Global system of interconnected computer networks using TCP/IP
Who invented the World Wide Web?
Tim Berners-Lee (1991)
WWW and Internet — same?
NO — Internet is the infrastructure; WWW is a service running on it
What is a Modem?
Modulator-Demodulator — converts digital signals to analog for transmission and back
Difference between Virus and Worm?
Virus needs a host file; Worm self-replicates without a host
What is a Trojan horse?
Malware disguised as legitimate software
What is Malware?
Umbrella term for all malicious software (virus, worm, trojan, spyware, ransomware)
What is Phishing?
Fake websites/emails that steal login credentials by impersonating legitimate services
What is an Operating System?
System software that manages hardware and software resources — Windows, Linux, Android
Compiler vs Interpreter?
Compiler translates whole program at once; Interpreter translates line by line
What is Cloud Computing?
Using computing resources (storage, processing) over the Internet instead of local hardware
PARAM series supercomputers developed by?
C-DAC (Centre for Development of Advanced Computing)
India's first supercomputer?
PARAM 8000 (1991) — developed by C-DAC
What is Bandwidth?
Maximum data transmission rate of a network connection — measured in Mbps/Gbps
USB stands for?
Universal Serial Bus
What is Encryption?
Converting data into coded form so only authorised parties can read it
Sophia (2017) is?
A humanoid robot that received Saudi Arabian citizenship in October 2017
Common Exam Traps
'Internet and WWW are the same' → FALSE. Internet = global network infrastructure. WWW = one service running on it. Email is another Internet service, not part of WWW.
'RAM stores data permanently' → FALSE. RAM is volatile — data is lost when power is switched off. ROM is non-volatile.
'A virus spreads by itself through a network' → FALSE. That's a WORM. A virus needs to attach to a host file and spread when that file is shared.
'Cache memory is the same as RAM' → FALSE. Cache is faster and smaller than RAM; it sits between CPU and RAM to speed up data access.
'PARAM supercomputers are made by ISRO' → FALSE. PARAM series is developed by C-DAC. ISRO made SAGA-220.
'The first computer was UNIVAC' → FALSE. UNIVAC was the first commercial computer (1951). ENIAC (1946) was the first electronic general-purpose computer.
'More RAM means faster processor speed' → FALSE. RAM affects how many programs run simultaneously; processor speed depends on CPU clock speed (GHz).
'Bluetooth is a type of Internet' → FALSE. Bluetooth is a short-range wireless PAN technology — it does NOT require Internet connection.
Computer questions in SSC are about memory types, networking, and security threats — learn the definitions, not the tech.
