Class 11 Information Technology (802)

Unit 1 – Computer Organisation

Computer Components, I/O Devices, Storage Devices and Memory Units

Learning Objectives

After studying this topic, students will be able to:

• Identify various components of a computer.

• Understand the functions of different computer components.

• Explain the purpose and use of Input and Output (I/O) devices.

• Identify different types of storage devices.

• Differentiate between primary and secondary storage.

• Understand different memory units used in computers.

• Convert between common units of digital storage.

• Compare different storage devices based on capacity, speed and portability.

Components of a Computer

A computer system is made up of several hardware components that work together to accept data, process it, store it and produce useful information.

The major components are:

The major functional components are:

1. Input Devices

2. Central Processing Unit

3. Primary Memory

4. Secondary Storage

5. Output Devices

1. Input Devices

An input device is a hardware device used to enter data and instructions into a computer.

Input devices convert information supplied by the user into a form that the computer can process.

Common Input Devices

1.1 Keyboard

A keyboard is one of the most common input devices.

It is used to enter:

• Letters

• Numbers

• Symbols

• Commands

• Special characters

Main Keys on a Keyboard

• Alphabet keys

• Number keys

• Function keys

• Arrow keys

• Control keys

• Enter key

• Spacebar

• Backspace

• Shift

• Ctrl

• Alt

Use: Typing documents, entering data and giving commands.

1.2. Mouse

A mouse is a pointing device used to control the pointer on the screen.

Common Mouse Operations

• Click

• Double-click

• Right-click

• Drag and drop

• Scroll

Use: Selecting objects, opening files, navigating applications and interacting with graphical interfaces.

1.3 Scanner

A scanner converts physical documents or photographs into digital form.

Example:

A printed photograph → Scanner → Digital image

Uses:

• Scanning documents

• Digitising photographs

• Creating electronic records

1.4 Microphone

A microphone is an input device used to capture sound.

Uses:

• Voice recording

• Video conferencing

• Online classes

• Voice commands

• Audio recording

1.5 Webcam

A webcam captures images and video and sends them to the computer.

Uses:

• Video calls

• Online classes

• Video recording

• Web conferencing

1.6 Touchscreen

A touchscreen allows users to interact directly with a display by touching it.

A touchscreen can act as both an input and output device.

Examples:

• Smartphones

• Tablets

• ATMs

• Information kiosks

1.7 Barcode Reader

A barcode reader scans barcodes and sends the information to a computer.

Uses:

• Supermarkets

• Inventory systems

• Libraries

• Warehouses

1.8 QR Code Reader

A QR code reader or camera can scan QR codes containing information such as:

• Website links

• Payment information

• Contact details

• Product information

1.9 Joystick

A joystick is a pointing/input device commonly used for controlling games and simulations.

1.10 Biometric Devices

Biometric devices identify people using physical or behavioural characteristics.

Examples include:

• Fingerprint scanner

• Iris scanner

• Face recognition camera

Uses:

• Attendance systems

• Security

• Authentication

• Access control

2. Output Devices

An output device presents processed information from the computer to the user.

Common Output Devices

• Monitor

• Printer

• Speakers

• Headphones

• Projector

• Plotter

2.1. Monitor

A monitor is a display device that shows text, images, videos and other graphical information.

Common Display Technologies

• LCD

• LED

• OLED

Important Characteristics

• Screen size

• Resolution

• Refresh rate

• Display quality

2.2. Printer

A printer produces information on paper or another physical medium.

This physical output is called a hard copy.

Printers can broadly be classified as:

Impact Printers

These printers produce output by physically striking an ink ribbon or similar mechanism.

Example:

• Dot Matrix Printer

Non-Impact Printers

These printers produce output without physically striking the paper.

Examples:

• Inkjet Printer

• Laser Printer

2.3. Speakers

Speakers convert electrical/digital audio signals into sound.

Uses:

• Music

• Videos

• Online classes

• Games

• Notifications

2.4. Headphones

Headphones provide audio output directly to the user.

They are useful when private listening is required.

2.5. Projector

A projector displays computer output on a large screen or wall.

Uses:

• Classroom teaching

• Presentations

• Meetings

• Training sessions

• Home entertainment

2.6. Plotter

A plotter is an output device designed to produce large and precise drawings.

It has traditionally been used for:

• Engineering drawings

• Architectural plans

• Maps

• Large technical graphics

Input vs Output Devices

Remember

Input → Computer → Output

I/O Devices

I/O stands for Input/Output.

I/O devices allow a computer to communicate with the outside world.

Some devices can perform both input and output functions.

Examples

A touchscreen, for example, displays information to the user and also accepts touch commands.

Storage Devices

Storage devices are hardware components used to save digital data.

Data may include:

• Documents

• Images

• Videos

• Music

• Programs

• Databases

• Backups

Storage is broadly divided into:

1. Primary Memory

Primary memory is memory that can be accessed directly by the CPU for active processing.

Important types include:

• RAM

• ROM

• Cache memory

Primary memory is generally faster than secondary storage.

1.1. RAM

RAM = Random Access Memory

RAM stores programs and data that are currently being used.

Characteristics

• Fast

• Directly accessible by the CPU

• Generally volatile

• Used for temporary working data

Example

When you open a web browser, the operating system loads the required program and data into RAM.

If the computer is switched off, information stored only in RAM is normally lost.

1.2. ROM

ROM = Read Only Memory

ROM is non-volatile memory that retains its contents when power is removed.

It is commonly used for storing firmware and other instructions needed by a computer or electronic device.

Characteristics

• Non-volatile

• Retains information without power

• Used for firmware

1.3. Cache Memory

Cache is a very fast memory located close to or within the CPU.

It stores frequently accessed data and instructions to reduce the time required for the CPU to obtain them.

Memory Speed Concept

The exact speed and hierarchy depend on the computer system, but the general principle is that smaller, CPU-near memories are faster.

2. Secondary Storage

Secondary storage is used for long-term storage of data and programs.

Unlike RAM, secondary storage is generally non-volatile.

Examples:

• Hard Disk Drive

• Solid State Drive

• USB Flash Drive

• Memory Card

• Optical Disc

2.1. Hard Disk Drive (HDD)

A Hard Disk Drive stores data using magnetic storage on rotating disks called platters.

Advantages

• Large storage capacities

• Relatively low cost per GB

• Suitable for storing large amounts of data

Disadvantages

• Mechanical moving parts

• Generally slower than SSDs

• More sensitive to physical shock

Uses

• Desktop computers

• Laptops

• Servers

• Backup storage

2.2. Solid State Drive (SSD)

An SSD stores data using flash memory and has no traditional moving mechanical parts.

Advantages

• Fast

• Quiet

• Low power consumption

• More resistant to physical shock than HDDs

• Faster boot and application loading

Disadvantages

• Usually costs more per GB than HDDs

• Flash memory has a finite write endurance, although modern SSDs are designed for substantial use

2.3. HDD vs SSD

2.4. USB Flash Drive

A USB flash drive is a portable storage device that uses flash memory.

Uses

• Transferring files

• Carrying documents

• Backing up data

• Installing software

• Sharing files

It is commonly connected through a USB port.

2.5. Memory Card

Memory cards are small removable flash storage devices.

Examples include:

• SD Card

• microSD Card

Uses

• Smartphones

• Digital cameras

• Tablets

• Action cameras

• Embedded devices

2.6. Optical Discs

Optical discs use laser technology to read and/or write information.

Examples:

• CD

• DVD

• Blu-ray Disc

Uses

• Media distribution

• Software distribution

• Data archiving

Optical discs are less commonly used for everyday storage today than USB drives, SSDs and cloud storage.

2.7. Cloud Storage

Cloud storage allows users to store data on remote servers accessed through a network, usually the Internet.

Examples include services that provide online file storage and synchronisation.

Advantages

• Accessible from multiple devices

• Useful for backup and synchronisation

• Easy file sharing

• No need to carry physical storage

Limitations

• Internet access may be required

• Storage may involve subscription costs

• Security and privacy depend on the service and account settings

Primary vs Secondary Storage

Memory Units

Computers represent and store information digitally.

The smallest commonly used unit of digital information is the bit.

Bit

A bit stands for binary digit.

It can have one of two values:

0 or 1

Byte

A byte consists of 8 bits.

1 Byte = 8 bits

A byte is commonly used as a basic unit for measuring storage capacity.

27. Common Storage Units

The commonly used units are:

Memory Unit Conversion

Example 1

Convert 4 KB into bytes.

Using:

1 KB = 1024 bytes

Therefore:

4 × 1024 = 4096 bytes

Answer:

4 KB = 4096 bytes

Example 2

Convert 2 MB into KB.

1 MB = 1024 KB

Therefore:

2 × 1024 = 2048 KB

Answer:

2 MB = 2048 KB

Example 3

Convert 3 GB into MB.

1 GB = 1024 MB

Therefore:

3 × 1024 = 3072 MB

Answer:

3 GB = 3072 MB

Bit and Byte – Difference

Important

Do not confuse:

b = bit

B = Byte

For example:

100 Mbps means 100 megabits per second.

100 MB means 100 megabytes.

30. Storage Capacity Examples

*Binary convention commonly used in school-level calculations.

Memory Hierarchy

Memory hierarchy represents different levels of computer storage based broadly on speed, cost and capacity.

Generally:

• Higher levels are faster and more expensive per unit of storage.

• Lower levels provide greater capacity at lower cost per unit.

Volatile and Non-Volatile Memory

Volatile Memory

Volatile memory loses its stored contents when power is removed.

Example:

RAM

Non-Volatile Memory

Non-volatile storage retains data even when power is removed.

Examples:

• ROM

• SSD

• HDD

• USB Flash Drive

• Memory Card

Internal and External Storage

Internal Storage

Storage installed inside a computer.

Examples:

• Internal SSD

• Internal HDD

External Storage

Storage that can be connected and disconnected from the computer.

Examples:

• USB Flash Drive

• External HDD

• External SSD

• Memory Card

Quick Comparison of Storage Devices

*Requires network/Internet access where applicable.

How to Choose a Storage Device?

The appropriate storage device depends on the requirement.

For fast computer performance

SSD

For large amounts of relatively inexpensive storage

HDD

For carrying small amounts of data

USB Flash Drive

For smartphones and cameras

Memory Card

For accessing files from multiple locations

Cloud Storage

For backup

A combination of local and cloud/off-site backup can be useful.

Identification Activity

Identify the following components:

Important Exam Questions

Very Short Answer Questions

Q1. What is an input device?

An input device is a hardware device used to enter data and instructions into a computer.

Q2. Give two examples of output devices.

Monitor and printer.

Q3. What is RAM?

RAM is Random Access Memory. It is volatile primary memory used to store data and programs currently being processed.

Q4. What is SSD?

SSD stands for Solid State Drive. It is a storage device that uses flash memory to store data.

Q5. What is the smallest commonly used unit of digital information?

Bit.

Q6. How many bits are there in one byte?

8 bits.

Q7. Name two secondary storage devices.

HDD and SSD.

Q8. What is cloud storage?

Cloud storage is a service in which data is stored on remote servers and accessed through a network.

Short Answer Questions

Q1. Differentiate between input and output devices.

Input devices are used to send data and instructions to the computer, whereas output devices are used to present processed information to the user.

Examples of input devices include keyboard, mouse and scanner.

Examples of output devices include monitor, printer and speakers.

Q2. Differentiate between RAM and ROM.

Q3. Differentiate between HDD and SSD.

An HDD uses magnetic storage on rotating disks, whereas an SSD uses flash memory and has no traditional moving mechanical parts.

SSDs generally provide faster access and are more resistant to physical shock, while HDDs generally offer lower cost per GB.

Q4. Explain the difference between primary and secondary storage.

Primary memory is used directly during active processing and includes RAM and cache. Secondary storage is used for long-term storage and includes devices such as HDDs, SSDs and USB drives.

Long Answer Questions

Q1. Explain different types of I/O devices with examples.

Input devices allow users to provide data to the computer. Examples include keyboard, mouse, scanner, microphone, webcam and barcode reader.

Output devices present processed information to users. Examples include monitor, printer, speakers, headphones and projector.

Some devices, such as touchscreens and multifunction devices, can perform both input and output functions.

Q2. Explain different storage devices used in computers.

Common storage devices include HDDs, SSDs, USB flash drives, memory cards and optical discs.

HDDs use magnetic storage and are useful for large-capacity storage. SSDs use flash memory and generally provide faster performance. USB drives and memory cards are portable flash storage devices. Optical discs use laser technology to read and write data.

Cloud storage provides another method of storing and accessing data remotely through a network.

Fill in the Blanks

1. ________ is used to enter text into a computer.
   Answer: Keyboard

2. ________ is used to display visual output.
   Answer: Monitor

3. ________ stands for Random Access Memory.
   Answer: RAM

4. ________ stands for Solid State Drive.
   Answer: SSD

5. One byte contains ________ bits.
   Answer: 8

6. ________ is a volatile memory.
   Answer: RAM

7. A ________ converts a paper document into a digital image.
   Answer: Scanner

8. A ________ is commonly used to produce hard-copy output.
   Answer: Printer

True or False

1. A keyboard is an input device.
   True

2. A monitor is an input device only.
   False

3. RAM is normally volatile.
   True

4. SSDs use traditional rotating magnetic platters.
   False

5. A byte contains 8 bits.
   True

6. A touchscreen can provide both input and output.
   True

7. HDDs use magnetic storage.
   True

8. A printer is an output device.
   True

Multiple Choice Questions

1. Which of the following is an input device?

A. Monitor
B. Printer
C. Keyboard
D. Speaker

Answer: C. Keyboard

2. Which component performs arithmetic and logical operations?

A. CU
B. ALU
C. RAM
D. ROM

Answer: B. ALU

3. Which memory is volatile?

A. ROM
B. RAM
C. SSD
D. HDD

Answer: B. RAM

4. Which storage device uses flash memory?

A. SSD
B. HDD
C. Magnetic tape
D. Mechanical diskette

Answer: A. SSD

5. One byte is equal to:

A. 2 bits
B. 4 bits
C. 8 bits
D. 16 bits

Answer: C. 8 bits

6. Which device is commonly used to produce hard-copy output?

A. Scanner
B. Printer
C. Mouse
D. Microphone

Answer: B. Printer

7. Which device can act as both an input and output device?

A. Keyboard
B. Touchscreen
C. Speaker
D. Mouse

Answer: B. Touchscreen

8. Which is generally faster?

A. HDD
B. SSD
C. Optical disc
D. Magnetic tape

Answer: B. SSD

43. Quick Revision Chart

Key Points to Remember

• Keyboard, mouse and scanner are common input devices.

• Monitor, printer and speakers are common output devices.

• Touchscreen can perform both input and output functions.

• CPU performs processing and controls operations.

• ALU performs arithmetic and logical operations.

• RAM is volatile primary memory.

• ROM is non-volatile memory.

• Cache is very fast memory used to improve CPU access to frequently needed data.

• HDD uses magnetic storage.

• SSD uses flash memory.

• USB drives and memory cards are portable flash storage devices.

• Cloud storage stores data on remote servers accessible through a network.

• 1 Byte = 8 bits.

• For school-level calculations, 1 KB = 1024 Bytes, 1 MB = 1024 KB, and so on, unless the question specifies another convention.

• b = bit and B = Byte.

One-Minute Revision

Input

Keyboard → Mouse → Scanner → Microphone → Webcam

Output

Monitor → Printer → Speakers → Projector

Primary Memory

RAM → ROM → Cache

Secondary Storage

HDD → SSD → USB Drive → Memory Card → Optical Disc

Memory Units

Bit → Byte → KB → MB → GB → TB → PB

Remember

8 bits = 1 Byte

Input → Processing → Output

RAM = Volatile

ROM = Non-volatile

HDD = Magnetic

SSD = Flash

Touchscreen = Input + Output