International Organisations — UN, World Bank & Trade Bodies

Why This Chapter Matters

RRB Group D papers carry 2 to 3 questions on basic computer awareness in the General Science and General Awareness section, and RRB NTPC, SSC MTS, and most state police exams ask the same style of question year after year. That sounds small until you realise these are among the easiest marks on the whole paper. A question on CPU or RAM does not need you to solve anything. It needs you to have seen the term once, calmly, without panic. This chapter gives you that one calm read.

Here is the trap almost every first-time aspirant falls into: mixing up hardware and software, or mixing up the CPU with the whole computer box. Students walk into the exam thinking the CPU is the big grey box sitting under the table. It is not. The CPU is one small chip inside that box. The box itself is called the cabinet or system unit, and it holds the CPU, the RAM, the hard disk, and several other parts. Keep that distinction sharp and you will already beat half the room on this topic. We will build your understanding the way a mechanic explains a car engine to a new driver: start with what the machine actually does, then open the bonnet and name the parts, then talk about what runs inside it, and finally step outside to the internet and email, the tools you already touch every single day on your phone.

1. What Is a Computer

A computer is a machine that takes in data, processes it by following instructions, and gives out a result. That is the entire definition, and exams love testing it in one line: Input, Process, Output. Think of a computer like a kitchen. You bring in raw vegetables (input), the cook chops and fries them following a recipe (processing), and a finished dish arrives at your table (output). The recipe is the equivalent of a computer program, a set of step-by-step instructions.

Every computer, from a giant government data centre to the smartphone in your pocket, works on this same input-process-output cycle. Where they differ is size, speed, and purpose. A supercomputer solves massive scientific problems, like weather prediction, at extreme speed. A mainframe computer is used by banks and railways to process huge volumes of transactions reliably. A desktop or laptop is what you and I use daily for typing, browsing, and studying. A microcomputer is the smallest general-purpose category, and your laptop actually falls under this class too, despite sounding tiny only in name.

Exam trap: Do not confuse a computer with a calculator. A calculator can only do arithmetic. A computer can be reprogrammed to do almost anything, from writing a letter to playing a video, because it follows changeable instructions rather than one fixed function.

A Short Look Back

You do not need dates for every computer generation, but exams sometimes ask which generation used which technology, so remember this short chain: the first generation used vacuum tubes, huge glass valves that generated enormous heat. The second generation replaced these with transistors, smaller and cooler. The third generation introduced integrated circuits (ICs), tiny chips holding many transistors together. The fourth generation, the one we still live in, uses the microprocessor, a single chip that packs an entire processing unit. Talk of a fifth generation usually points to artificial intelligence, still developing rather than fully arrived.

Memory hook: Remember the chain as V-T-I-M: Vacuum tube, Transistor, IC, Microprocessor. Say it like a small drumbeat, each word one generation smaller and faster than the last.

2. Hardware — The Parts You Can Touch

Hardware means every physical part of the computer, anything you can pick up, plug in, or physically damage by dropping it. Software, by contrast, is the invisible set of instructions that hardware follows. If hardware is the body, software is the mind telling that body what to do. Keep this pairing in your head, because exams frequently ask you to sort a list of items into hardware or software.

The CPU — The Brain

The Central Processing Unit (CPU) is often called the brain of the computer, and this is one of the most repeated lines in exam papers. The CPU carries out instructions, does calculations, and controls the flow of data between other parts. It sits inside the system cabinet as a small chip, roughly the size of a matchbox, plugged into the motherboard.

The CPU itself has three working parts you should know by name:

• Control Unit (CU): directs traffic. It tells other parts of the computer what to do and when, much like a traffic constable at a busy Delhi crossing, waving one lane of vehicles forward while holding the rest.
• Arithmetic and Logic Unit (ALU): performs all mathematical calculations (addition, subtraction) and logical comparisons (is this value bigger than that one, is this true or false).
• Memory Unit / Registers: tiny, extremely fast storage spots inside the CPU itself, holding the data the CPU is working on right this second.

Exam trap: Many students write "CPU" when a question actually means "computer." Read carefully. If a question says "the brain of the computer," the answer is CPU. If it says "the complete machine," it usually means the whole system, cabinet included.

The Motherboard

The motherboard is the large flat circuit board inside the cabinet that connects everything else together: the CPU, the RAM, the hard disk, and expansion cards all plug into it. Picture it as the floor plan of a house. Every room (each hardware part) sits on that floor plan, and wiring runs beneath it connecting every room to every other room.

Memory — RAM and ROM

Computer memory splits into two broad types, and exams love this pair because they behave oppositely.

RAM (Random Access Memory) is temporary, working memory. It holds data and instructions only while the computer is switched on and actively using them. The moment you turn off the power, everything in RAM disappears. Think of RAM as your study desk. While you are working, your open books, notebook, and pen sit on the desk within easy reach. The moment you clear the desk at night, nothing on it survives till morning unless you had already saved it into a cupboard.

ROM (Read Only Memory) is permanent and non-volatile, meaning it keeps its data even after the power goes off. ROM usually stores the basic startup instructions the computer needs the instant it is switched on, before the operating system itself loads. That cupboard from our analogy, the one that keeps your notes safe overnight, is ROM.

Exam trap: RAM is volatile (data lost on power off). ROM is non-volatile (data stays). This single pair of words, volatile versus non-volatile, is asked constantly. Do not swap them.

Storage Devices

Storage is different from RAM. Storage holds your files permanently, whether the computer is on or off, and you choose what to keep there.

• Hard Disk Drive (HDD): the traditional storage device, using spinning magnetic disks to store large amounts of data cheaply.
• Solid State Drive (SSD): a newer, faster storage device with no moving parts, using flash memory chips instead of spinning disks. SSDs cost more per gigabyte but load files far quicker.
• Pen drive / USB flash drive: a small, portable flash storage device you plug into a USB (Universal Serial Bus) port to carry files between computers.
• CD, DVD: older optical storage discs, read using a laser. A CD typically holds around 700 MB, a DVD holds several gigabytes.
• Memory card: flash storage commonly used in cameras and phones.

Input Devices

Input devices let you feed data or commands into the computer.

• Keyboard: the most common input device, used to type text and commands.
• Mouse: a pointing device that lets you click, select, and drag items on screen.
• Scanner: converts a printed document or photo into a digital image the computer can store.
• Microphone: captures sound as input.
• Webcam: captures video as input, widely used for video calls.
• Joystick: used mainly for gaming, sends directional input.
• Barcode reader: scans barcodes, common at store billing counters, a sight you have likely seen at any Kirana or supermarket checkout.

Output Devices

Output devices show or produce the result of processing, in a form you can see, hear, or hold.

• Monitor (VDU, Visual Display Unit): shows text, images, and video on screen. It is output only, it does not process anything itself.
• Printer: produces a paper copy of a digital document. Common types are inkjet (sprays liquid ink) and laser (uses toner powder and heat, faster and sharper for text-heavy pages).
• Speaker: produces sound output.
• Projector: displays computer output onto a large screen or wall, common in classrooms and offices.

Exam trap: A printer can sometimes be tested as an output device that is also occasionally grouped separately as a "hard copy" device, while a monitor gives only a "soft copy" (on-screen, not physical). If a question asks which device gives permanent, physical output you can hold, the answer is printer, not monitor.

Some devices work as both input and output. A touchscreen accepts your finger tap as input and displays the screen as output, both at once. A modem sends and receives data. Keep an eye out for such "both" devices in tricky exam options.

Memory hook for input/output sorting: Ask yourself, "Does this device put something INTO the computer, or does it bring something OUT for me to see or hear?" A keyboard puts letters in. A monitor brings a picture out. Read every device with that one simple test and you will rarely get sorting questions wrong.

3. Software — The Instructions Behind the Screen

Software is a collection of programs and data that tells hardware what to do. Without software, even the most expensive hardware is a dead, silent box. Software splits mainly into two categories.

System Software

System software manages the computer itself and lets other programs run. The most important example is the Operating System (OS). The OS is the master program that manages hardware resources, runs other software, and gives you a way to interact with the machine, usually through icons, windows, and menus. Common operating systems include Windows, Linux, macOS, and, for mobile phones, Android and iOS.

Think of the operating system as the station master at a railway station. Trains (programs) arrive and depart, platforms (memory and CPU time) get allocated, and passengers (your commands) get directed to the right place, all managed by one controlling authority so that chaos does not break out. Without a station master, or without an OS, nothing runs in an organised way.

Other system software includes device drivers, small programs that let the OS talk to specific hardware like a printer or a graphics card, and utility software, which does maintenance jobs like scanning for viruses or compressing files.

Application Software

Application software is written for a specific task the user wants done, like typing a letter, editing a photo, or browsing a website. Examples include word processors (like MS Word), spreadsheet programs (like MS Excel), presentation software (like MS PowerPoint), and web browsers (like Google Chrome or Mozilla Firefox).

Exam trap: Students often list "Windows" as application software because they use it directly every day. Windows is system software, an operating system. MS Word, which you open to type inside Windows, is the application software.

File and Folder Basics

A file is a named collection of data stored on a computer, such as a document, photo, or song. A folder (also called a directory) is a container used to organise related files together, much like a physical file folder on an office desk holding related papers. Every file has a file extension, a short tag after a dot in its name, showing what type of file it is and which program should open it. For example, .docx is a Word document, .xlsx is an Excel spreadsheet, .jpg or .png is an image, .pdf is a portable document format file, and .mp3 is an audio file.

4. Units of Data Storage

Exams frequently test the storage size chain, because it is a clean, memorisable sequence.

A bit is the smallest unit of data, a single 0 or 1. Eight bits make one byte, and one byte typically stores a single character, like the letter "A." Beyond that, storage grows in steps of roughly a thousand times each:

1,024 bytes = 1 Kilobyte (KB) 1,024 KB = 1 Megabyte (MB) 1,024 MB = 1 Gigabyte (GB) 1,024 GB = 1 Terabyte (TB)

Memory hook: Remember Bit, Byte, KB, MB, GB, TB as a growing family tree: a bit is a newborn, a byte is a toddler with eight fingers held up (eight bits), and each generation after that grows roughly a thousand times bigger than its parent.

Exam trap: The multiplier is 1,024, not a round 1,000, because computers count in binary (base 2), and 1,024 is 2 raised to the power 10. A question that uses 1,000 as the multiplier is using a rounded, everyday approximation, not the strict computing definition.

5. Internet Basics

The Internet is a massive network connecting millions of computers worldwide, allowing them to share data and communicate. Think of it as the country's road and rail network scaled up to a planetary level: individual computers are like towns, and the internet is the web of highways connecting every town to every other town, letting goods (data) travel between them.

A web browser is the application software you use to access the internet, like Chrome, Firefox, or Edge. A website is a collection of related web pages stored under one address. A web page is a single document on that website. The URL (Uniform Resource Locator) is the specific address you type or click to reach a page, such as www.example.com.

WWW (World Wide Web) is often confused with the internet itself, but they are not the same thing. The internet is the physical and logical network of connected computers. The WWW is a system of linked documents and pages that runs on top of that network, accessed through browsers. The internet is the road; the WWW is one particular kind of traffic, made of linked pages, travelling on that road.

HTTP (HyperText Transfer Protocol) is the rule set browsers and websites use to exchange web page data. HTTPS is the secure version, with the "S" standing for Secure, meaning the data traveling between your browser and the website is encrypted, scrambled so an outsider cannot easily read it. Always look for HTTPS, shown with a small padlock icon, before entering sensitive details like passwords on a website.

Wi-Fi is a wireless technology letting devices connect to a network without cables, using radio waves over a short range. ISP (Internet Service Provider) is the company that actually supplies your internet connection, such as through a broadband cable or mobile data plan.

Search Engines

A search engine, such as Google, is a tool that helps you find information on the internet by searching through indexed web pages and returning the most relevant results for your typed query. It does not create information; it finds and ranks existing pages.

Downloading and Uploading

Downloading means copying a file from the internet onto your own device. Uploading means sending a file from your device onto the internet or a remote server. Exam trap: Students frequently swap these two directions under exam pressure. Remember it this way: "down" comes toward you, onto your device, while "up" goes away from you, into the internet.

6. Email Basics

Email (Electronic Mail) lets you send and receive digital letters instantly over the internet. An email address always follows one strict pattern: username@domainname.com, where the @ symbol separates your personal username from the mail provider's domain, like gmail.com or yahoo.com.

Every email has three key destination fields you should know clearly:

• To: the main recipient of the email, the person you are directly writing to.
• CC (Carbon Copy): additional people who receive a copy, and every recipient can see who else was CC'd. The term comes from old-fashioned carbon paper, once used to make duplicate copies of a handwritten or typed letter without retyping it.
• BCC (Blind Carbon Copy): additional people who receive a copy, but their names stay hidden from every other recipient. Nobody on the To or CC list can see who was BCC'd.

An attachment is a file, like a photo or document, sent along with the email rather than typed into the body. The subject line is a short summary of the email's topic, shown before the recipient even opens the message. An inbox holds received mail, while the outbox or sent folder holds mail you have sent. Spam, sometimes called junk mail, refers to unwanted, unsolicited messages, often advertisements or scam attempts, that most email services filter into a separate folder automatically.

Exam trap: CC recipients are visible to everyone; BCC recipients are hidden from everyone else. A question that asks "which field hides the recipient's identity from other recipients" is asking about BCC, not CC.

7. Common Computer Terms and Abbreviations

Group D and NTPC papers love picking one abbreviation and asking you to expand it. Here is a working list you should recognise instantly, since a solid grip here converts directly into free marks with almost no extra reasoning required.

USB (Universal Serial Bus) is a common standard connector for linking devices like pen drives, keyboards, and mice to a computer. PDF (Portable Document Format) is a file format that preserves a document's exact layout across different devices and software, which is why exam admit cards and answer keys are almost always released as PDFs. GUI (Graphical User Interface) is a way of interacting with a computer using visual elements, icons, windows, and a mouse pointer, rather than typing text commands. Its older opposite, CLI (Command Line Interface), requires the user to type exact text commands to control the computer.

LAN (Local Area Network) connects computers within a small area, like one office building or a school. WAN (Wide Area Network) connects computers over a large geographic area, potentially spanning cities or countries; the internet itself is the biggest WAN of all. Bluetooth is a short-range wireless technology used to connect nearby devices, like a phone and a wireless earphone, without cables.

Cloud storage means saving your files on remote servers accessed over the internet, rather than only on your own device's local storage, letting you reach those files from any connected device. A virus is a harmful program designed to damage files or disrupt normal computer operation, often spreading by attaching itself to other files. Antivirus software detects and removes such harmful programs. A firewall is a security system, hardware or software, that monitors and controls incoming and outgoing network traffic, acting like a security guard checking every visitor at a gate before letting them through.

Cache memory is a small, very fast memory located close to the CPU, storing frequently used data so the processor does not need to fetch it repeatedly from slower main memory, saving valuable time. Booting is the process of starting up a computer and loading its operating system into memory. A cold boot starts the computer from a fully powered-off state, while a warm boot restarts a computer that is already running, without cutting the power completely.

Cursor is the blinking indicator on screen showing where your next typed character will appear. Icon is a small picture representing a file, folder, or program, letting you open it with a click instead of typing a command. Desktop in a software sense refers to the main screen you see after your computer starts up, showing icons and a taskbar, distinct from the desktop computer hardware category mentioned earlier in this chapter. Watch for this exact wording trick in exam options.

Quick Revision — One-Line Facts

• A computer works on the cycle: Input, Process, Output.
• CPU is called the brain of the computer; it has the Control Unit, ALU, and registers.
• RAM is temporary and volatile; data is lost when power is off.
• ROM is permanent and non-volatile; data survives after power off.
• Motherboard is the main circuit board connecting all internal hardware parts.
• HDD uses spinning magnetic disks; SSD uses flash memory with no moving parts.
• Monitor is an output device, giving a "soft copy" only, not a physical printout.
• Printer gives a "hard copy," a physical, paper output.
• Keyboard, mouse, scanner, and microphone are common input devices.
• Touchscreen works as both an input and output device.
• System software manages the computer; application software does a specific user task.
• Operating System (OS) is the master system software managing hardware and other programs.
• Windows, Linux, and macOS are operating systems; MS Word and Chrome are application software.
• 8 bits make 1 byte; storage grows in steps of 1,024 after that (KB, MB, GB, TB).
• The Internet is the global network of connected computers.
• WWW is a system of linked pages running on top of the internet, not the same as the internet itself.
• HTTPS is the secure, encrypted version of HTTP, shown with a padlock icon.
• Wi-Fi allows wireless connection to a network over a short range using radio waves.
• ISP is the company supplying your internet connection.
• A search engine finds and ranks existing web pages; it does not create new information.
• Downloading brings a file onto your device; uploading sends a file onto the internet.
• Email format is always username@domainname.com.
• CC recipients are visible to all; BCC recipients stay hidden from other recipients.
• USB is a common connector standard for external devices like pen drives.
• GUI uses icons and windows; CLI uses typed text commands.
• LAN covers a small area like an office; WAN covers a large area like a country.
• Bluetooth is short-range wireless technology for nearby devices.
• Antivirus software detects and removes harmful programs called viruses.
• Firewall monitors and controls network traffic for security.
• Cache memory is small, fast memory near the CPU storing frequently used data.
• Booting is the process of starting a computer and loading its operating system.

Memory Tables

Table 1: Hardware Categories at a Glance

Category	Purpose	Examples
Input devices	Feed data/commands into the computer	Keyboard, mouse, scanner, microphone, webcam
Output devices	Show or produce processed results	Monitor, printer, speaker, projector
Storage devices	Hold data permanently	HDD, SSD, pen drive, CD/DVD, memory card
Processing	Executes instructions	CPU (Control Unit, ALU, registers)
Memory (temporary)	Holds active working data	RAM
Memory (permanent, built-in)	Holds startup instructions	ROM
Connecting board	Links all internal parts together	Motherboard

Table 2: Key Abbreviations and Full Forms

Abbreviation	Full Form	One-line Meaning
CPU	Central Processing Unit	Brain of the computer; executes instructions
RAM	Random Access Memory	Temporary, volatile working memory
ROM	Read Only Memory	Permanent, non-volatile startup memory
HDD	Hard Disk Drive	Magnetic storage with spinning disks
SSD	Solid State Drive	Flash-based storage, no moving parts
USB	Universal Serial Bus	Standard connector for external devices
GUI	Graphical User Interface	Icon and window based interaction
CLI	Command Line Interface	Text command based interaction
LAN	Local Area Network	Network within a small area
WAN	Wide Area Network	Network across a large area
WWW	World Wide Web	Linked pages running over the internet
HTTP/HTTPS	HyperText Transfer Protocol (Secure)	Rules for exchanging web page data
ISP	Internet Service Provider	Company supplying internet access
PDF	Portable Document Format	Fixed-layout document file format
OS	Operating System	Master software managing hardware and programs

Table 3: Data Storage Units

Unit	Equal To
1 Byte	8 Bits
1 Kilobyte (KB)	1,024 Bytes
1 Megabyte (MB)	1,024 KB
1 Gigabyte (GB)	1,024 MB
1 Terabyte (TB)	1,024 GB

Practice MCQs

Q1. Which part of the computer is commonly called the "brain of the computer"? (a) Monitor (b) CPU (c) Keyboard (d) Printer

Q2. Which type of memory loses all its data as soon as the computer's power is switched off? (a) ROM (b) Hard Disk (c) RAM (d) Pen drive

Q3. Which of the following is an example of an output device? (a) Scanner (b) Keyboard (c) Monitor (d) Mouse

Q4. MS Word and Google Chrome are examples of which category of software? (a) System software (b) Application software (c) Operating system (d) Device driver

Q5. How many bits make one byte? (a) 4 (b) 8 (c) 16 (d) 1024

Q6. What does "WWW" stand for? (a) World Wide Web (b) World Wireless Web (c) Wide World Web (d) World Web Wire

Q7. In an email, which field allows you to send a copy to someone without other recipients knowing about it? (a) To (b) CC (c) BCC (d) Subject

Q8. Which of these devices works as both an input and an output device? (a) Monitor (b) Touchscreen (c) Printer (d) Speaker

Q9. Which part of the CPU performs mathematical calculations and logical comparisons? (a) Control Unit (b) Motherboard (c) Arithmetic and Logic Unit (d) RAM

Q10. Which of the following storage devices has no moving mechanical parts? (a) Hard Disk Drive (b) CD (c) Solid State Drive (d) DVD

Q11. What is the correct order of increasing storage size? (a) MB, KB, GB, TB (b) KB, MB, GB, TB (c) GB, MB, KB, TB (d) TB, GB, MB, KB

Q12. Which term describes a program designed to damage files or disrupt normal computer functioning? (a) Firewall (b) Virus (c) Cache (d) Driver

Q13. HTTPS is the secure version of HTTP. What does the "S" in HTTPS stand for? (a) Server (b) Software (c) Secure (d) System

Q14. Which software category directly manages computer hardware and lets other programs run, such as Windows or Linux? (a) Application software (b) Utility only (c) Operating system (d) Antivirus only

Q15. A LAN typically connects computers within which of the following? (a) An entire country (b) A small area like one office or school (c) Only two continents (d) Outer space satellites only

Answer Key

Q	Answer	Reason
1	(b) CPU	The CPU processes instructions and controls operations, earning the "brain" label; the monitor and printer are output devices only.
2	(c) RAM	RAM is volatile memory; ROM, hard disks, and pen drives are all non-volatile and retain data without power.
3	(c) Monitor	A monitor displays processed results, an output; scanner, keyboard, and mouse all feed data in, making them inputs.
4	(b) Application software	Both are user-facing tools for specific tasks; Windows/Linux would be the operating system category instead.
5	(b) 8	Eight bits combine to form one byte, the smallest unit that typically represents a single character.
6	(a) World Wide Web	WWW is the system of linked documents on the internet, distinct from the internet's physical network itself.
7	(c) BCC	BCC keeps that recipient's identity hidden from everyone else on the email; CC recipients remain visible to all.
8	(b) Touchscreen	A touchscreen accepts finger input and also displays output simultaneously, unlike a monitor which is output only.
9	(c) Arithmetic and Logic Unit	The ALU handles calculations and logical comparisons; the Control Unit directs operations instead of computing them.
10	(c) Solid State Drive	SSDs use flash memory chips with no spinning parts, unlike HDDs, CDs, and DVDs which all rely on moving mechanisms.
11	(b) KB, MB, GB, TB	Each unit is 1,024 times the one before it, moving from smallest to largest in this exact order.
12	(b) Virus	A virus damages or disrupts systems; a firewall and antivirus instead protect against such threats.
13	(c) Secure	HTTPS encrypts data between browser and website; the padlock icon confirms this secure connection.
14	(c) Operating system	The OS is the core system software managing hardware resources and running other programs on top of it.
15	(b) A small area like one office or school	LAN stands for Local Area Network; a WAN, not a LAN, covers large areas like whole countries.