11th Class (HSSC-I) Computer Science Key Point Notes - Unit-1 - Introduction to Computers Full Chapter Topic wise notes

11th Class (HSSC-I) Computer SLO Based Key Point Notes

(National Book Foundation - As Federal Textbook Board, Islamabad 

Based on National Curriculum Pakistan 2024 and Onward prescribed by Federal Board of Intermediate and Secondary Education, Islamabad, and All Pakistan Boards) 

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Unit-1 

"Introduction to Computers"

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Class 8 Computer Science MCQs for practice (All Units Exercise) 

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1.      Computer:

An electronic device that accepts data and instructions (input) from the user, performs operations accordingly (processing), and produces results (output).

 

2.      Main components of a computer:

Input devices, output devices, central processing units, storage devices, main memory, and communication devices.

 

3.      Computing devices:

Any device having embedding computer/processing chips.

Examples:

ATM, digital washing machines, Microwave ovens, A.C, etc.

 

 

 

4.      Basic Operations of a Computer:

 

i)        Input operation: 

It accepts data and instructions from input devices such as a Keyboard, Mouse, barcode reader, etc.

ii)      Processing operation: 

It performs operations, Arithmetic (+, -, *,/) and logical (comparison /relational)

 

iii)    Output operation: 

It displays results on output devices such as monitors or printers etc.

 

iv)    Storage operations: 

It writes data to a storage device such as USB, CD, hard disk, etc.

 

5.      Classification of digital Computer:

Computers can be classified into four categories on the basis of their shape, size, processing speed, and cost.

1. Supercomputers
2. Mainframe computer
3. Mini computers
4. Microcomputers

 

1.      Supercomputers:

Features:

• Largest computers.
• Most expensive.
• Most powerful.
• Designed to process complex calculations.
• Thousands of processors.
• Speed is measured in Tera flops(floating point operation per second)

Uses:

• Design and control of rockets and fighter planes.
• Weather forecasting.
• Nuclear research
• In Pakistan, they are used in SPARCO and Atomic Energy Research center.
• Manufactured by CRAY Inc. and IBM

2.      Mainframe computers:

Features:

• Less powerful, less expensive, and smaller than supercomputers.
• More powerful, expensive, and larger than any other computers.
• Very large storage capacity.
• Can execute trillions of instructions per second (TIPS).
• Can support up to thousands of users/terminals.

Uses:

• Used in large organizations like banks, universities, and scientific laboratories
• Also used as a web server.
• Example (IBM Enterprize EC12, HP 16500 series).

 

3.      Minicomputer:

Features:

• Less powerful, less expensive, and smaller than a mainframe.
• More powerful, expensive, and larger than microcomputers.
• Can support hundreds of users/terminals.
• Can process billions of instructions per second (BIPS)
• Used in industrial process control, scientific research, and small business organizations.

Uses:

• Can be used as database servers.
• Example IBM System /36 DEC PDP, HP 3000, etc.

 

4.      Microcomputers:

Features:

• Smallest and least expensive computers.
• It uses microprocessor chips. VLSI(very large-scale integration).
• General purpose computers.
• Can execute Millions of instructions per second (MIPS).
• Support a large variety of input and output devices (keyboard, mouse, monitor, printers, etc.)
• Also called personal computers.
• Support A large variety of applications.

Uses:

• Used in almost every field. (banks, stores, schools, homes, etc.)

6.      Modern Use of Computers in Today's Life:

 

1.      Mobile Computing:

• Small portable devices that allow people to access and share information.
• They use wireless networks.
• Mobile devices have limited functions.
• run on batteries
• Have a small display, less processing, and less memory

Examples: PDAs, tablet PCs, smartphones, etc.

 

2.      Internet of Things (IoT)

• Interconnection between a computer network and physical devices.
• Devices are equipped with wireless connectivity, embedded software, sensors, cameras microphones, etc.
• Smart devices which can interact with humans through a wireless connection.

Example: smart homes. House appliances such as AC, lights, and electronic devices can be controlled remotely via smartphones.

 

3.      Cloud computing:

• Using a remote server for storing and processing data.
• Eliminates the need for buying and installing computer systems and software at one’s place.
• Security and other services are provided by another company.

 

Advantages:

• Cost-effective. (does not need to buy and maintain the system).
• More secure and reliable.
• Access and share information from anywhere via the Internet.

 

Disadvantages:

• Requires a high-speed internet connection for accessing and uploading.
• Privacy and security risks.

 

Companies that provide cloud computing services:

Google, Microsoft, Citrix system and Amazon

4.      Data centers:

• A centralized location for collecting, storing, processing, and distributing vast amounts of data.
• Consists of servers, routers, switches, backup, etc.
• Data centers require air conditioning, file compression, and security services.
• It requires a room or an entire building.
• Banks, universities, and telecom companies require data centers.

 

7.      Computer Hardware and Software:

 

1.      Computer Software:

Software is a set of instructions given to computers for performing tasks and solving problems. Also called programs. 

Examples: Word processors, spreadsheets, games, database management systems, etc.

 

a)      Types of computer software:

Computer software can be classified into:

 

1. System software
2. Application software
3. Internet applications
4. Licensed software, open source software, shareware, and freeware.

 

1.       System software:

Software that controls and coordinates the activities of a computer system is called system software. It consists of programs designed to control hardware and manage software.

a)      Types of system software:

1. Operating system
2. Device drivers
3. Utility software
4. Language processors/ translators

1.      Operating system:

It controls and manages the hardware and software resources of the computer system and provides a user interface. A computer cannot work without an operating system.

Examples: Windows, LINUX, UNIX, MAC OS, Android, IOS, etc.

 

Tasks of the operating system:

• Loading and execution of programs.
• Allocating resources.
• Memory management.
• File management
• Storage management
• Providing user interface.
• Maintain security.
• Provide network facility.

 

2.      Device Drivers:

• Software that controls the operation of hardware devices.
• Any device attached to the computer will not work properly without device drivers.
• Device drivers are provided by device manufacturers.
• Plug and Play devices have their drivers preinstalled in Windows.

 

3.      Utility software:

• Perform functions that are beyond the capability of the operating system.
• Users can perform tasks easily and efficiently.

Examples: File manager, disk management utility, disk defragmenter, antivirus, file compression software, etc.

 

4.      Language processors/ translators:

• Computer can only understand machine language which is in the form of 0 and 1.
• Programs are written in assembly language or high-level language.
• Language processors convert programs written in assembly or high-level language into machine language.

 

 

Types of Language Processors:

There are three types of language processors

Assembler: 

It translates assembly language programs into machine language.

Compiler: 

it converts a high-level language program into machine language. The entire program is converted into machine language using the compiler.

Interpreter: 

It also converts a high-level language program into machine language. It translates one instruction at a time goes to the next instruction after executing the previous one.

 

2.      Application software:

Application software is used to perform a particular task. For example word processors, games, spreadsheet software, etc. 

Examples:

1. Productivity software.
2. Business software.
3. Entertainment software.
4. Educational software.

 

1.      Productivity software:

• Designed to perform daily activities effectively and efficiently.
• Word processors, spreadsheets, database management systems, and graphic software are a few examples.

2.       Business software: 

• It helps in performing business activities efficiently.
• For example payroll, inventory, accounting, etc.

3.      Entertainment software:

• It is used to entertain people
• Examples: games,, media players, music software, etc.

4.      Educational software:

• Used for learning purposes
• Examples: teaching about the human body, solar system, languages, typing, etc

 

3.      Internet Applications:

1. Web applications
2. Cloud computing applications
3. Social media network application

1.  Web applications:

• These programs run on a remote server.
• Users can interact with it using a browser or a client application.
• Examples: e-mail services, online banking, online ticket reservations, etc.

2.  Cloud computing applications:

• It supports cloud computing.
• Users can access data and applications stored on a remote server using this application

Examples: iCloud, Dropbox, etc.

 

3.  Social media network application:

• Social media allows people to create and exchange information, ideas, interests, etc.
• It connects users with their friends, families, or colleagues.

Some popular Social media network applications are

 

i)  Facebook:

• It is the most popular social media network application connecting billions of people around the world.
• It allows users to create profiles, exchange messages, and share photos videos, and links.
• Users can also create pages and groups based on common interests.

 

ii)  Twitter:

• It is a news and social networking service

• It allows users to broadcast short messages called tweets to other subscribers.

• People can share their views about current affairs or other topics.

 

iii)  WhatsApp;

• It is a free messaging service to exchange text, photos, audio or video, etc.
• It is very popular among people due to the features like audio and video call group chat, location sharing, etc.
• Available for all smartphone operating systems (iPhone, Android, Nokia, etc.)

 

 

 

4.      Licensed software, open source software, shareware/trial ware freeware, and firmware.

1.  Licensed software:

• A license is a legal agreement that gives the user the right to use the software.
• Licensed software is protected by copyright laws.
• One cannot make illegal copies of licensed software.
• Software copied or sold without the permission of the owner is called pirated software.

Example: Microsoft Windows, Microsoft Office, etc.

 

2.  Open source software:

• A software whose source code is available for users to study, change, or improve it.
• It is free for inspection modification and distribution.

Examples: LINUX, Open Office, etc.

3.  Shareware/trial ware:

• It is available free for a limited time period called a trial period.
• After the trial period expires user has to purchase the software.
• The trial version may have limited features or it stops working after it expires.

Examples: antivirus etc.

4.  Freeware:

• It is available free with full features for unlimited time.
• It may have some restrictions like personal or educational use.

Examples: Browsers, SKYPE, games, Viber, etc

 

5. Firmware:

• The intermediate form between hardware and software
• Software embedded in devices during manufacturing.
• Programs stored in it do not need to be changed.
• Data is not lost even when the power is off.

Examples: toys, appliances, ROM, etc.

 

 

Internet Application Security:

• Prevention against threats to internet applications.
• Threats may include malware attacks, data stealing, modification, or deletion by hackers.
• Security measures include firewall, anti-virus, spyware removal, and encryption/decryption.

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2.      Computer Hardware:

Hardware are physical components of the computer that can be seen and touched. (Tangible components). It included input devices, output devices, memory, processing, storage, etc.

Examples:  Keyboard, mouse, monitor, printer, circuitry, etc.

 

I.       Input devices

Input devices provide data and instructions to the computer. It accepts data in human-readable form and converts it into machine-readable form.

Examples: keyboard, mouse, microphone, etc.

 

1.       Keyboard:

• It is used to input data in the form of text.
• A keyboard has keys or buttons on it.
• It converts keys pressed to electric signals in digital form.
• It has alphabet keys, numeric keys, function keys, and special keys.
• Pointing Input Devices.
• Used to control the movement of the cursor on the screen.

 

2.       Mouse:

• Most Common pointing device.
• It detects motion on a surface and translates it into the motion of the pointer on the screen.
• Mouse Types: Mechanical mouse (having a ball rolling), optical mouse (having optical sensors), wireless mouse, etc.
• It can perform an operation such as selection, moving objects, opening files, etc. by clicking, dragging, etc.

3.       Trackball:

• It has a ball on top that is rolled with fingers.
• It is stationary on the surface.
• Also has buttons like a mouse performing similar operations.

4.       Joystick:

• It is used for playing games.
• It has a stick and buttons on it.
• The movement of objects on the screen is controlled by tilting the stick.

 

5.       Touch Screen:

• Both Input and output devices.
• Pressure-sensitive screen.
• A user interacts with the computer by touching the icons or text on the screen using fingers or a stylus.
• Mostly popular in smartphones, PDAs, navigators, tablet PCs, etc.

 

6.       Light Pen:

• Similar to a pen having a photo sensor at its tip.
• It is used for pointing and drawing on the screen.
• Provides better control and accuracy than a mouse and touch screen.
• Used for designing and engineering purposes.

 

7.       Touch Pad:

• It is a touch-sensitive surface.
• Sense the movement of fingers and control the pointer movement on the screen Accordingly.
• Used in laptop computers as an alternative to mouse.
• Also has two buttons like a mouse below it.

 

8.       Microphone:

• It is used for voice input.
• It converts audio signals into electrical signals.
• A sound card then converts electric signals into digital form.

 

9.       Digital Camera:

• It captures pictures and stores them in digital form.
• It has a memory card for storage.
• The images captured can be downloaded to the computer.
• Some digital cameras have LCDs to view images, and edit or delete them.

10.    Scanners:

It reads text or images from paper and stores them in a computer in digital form.

 

Types of scanners:

a)       Handheld scanner

b)       Flatbed scanner

c)       Barcode reader

 

a)      Handheld scanner:

• It is a handheld device that is moved over the image to be scanned.
• It must be moved with uniform speed to provide an image without distortion.
• They are slower than flatbed scanners.

 

b)     Flatbed scanner:

• It can scan entire images at a time.
• The image is placed face down on the glass and covered with a lid.

 

c)      Barcode reader:

• It scans bar code or UPC (Universal Product Code) on products.
• The barcode has information about the product like expiry date, price, etc.
• This information is given to computers for generating bills which makes faster checkouts.

 

d)     Magnetic Strip Card Reader:

• It reads information on a magnetic strip located on a plastic card.
• Information is stored in the form of magnetized spots.
• Information can be read by swiping the cards on the reader.

Examples: ATM cards, credit cards, driving licenses, etc.

II.    Output Devices:

Output devices display useful information.

Types of Output Devices:

Softcopy output: it is displayed on a screen in the form of text, images, video, etc.

Hardcopy output: it is in printed form on paper by a printer or plotter.

Sound output: output generated through speakers in the form of sound.

 

1.       Monitor: 

• Also called VDU( Video Display Unit)
• It produces soft copy output. (Text, graphics, video, animations, etc.)

 

Features:

1. Size: The monitor varies in size from 15 to 21 inches.
2. Colour: monitor can be black and white or RGB (colored).
3. Pixel: stands for picture element. It is a small dot on the monitor forming an image.
4. Resolution: numbers of pixels per square inch. The higher the resolution better the image quality.
5. Dot pitch. Distance between two pixels on the screen. A smaller dot pitch means higher resolution.

 

Types of monitor:

CRT, LCD, LED, etc.

 

a)      CRT (Cathode Ray Tube) Monitors:

• Similar to standard television sets.
• Heavier and consumes more power.
• It is a vacuum tube having an electron gun and a phosphor-coated screen.
• An electron gun sprays a beam of electrons which glows the phosphor-coated screen when striking it.
• Colored monitors have three electron guns and phosphor atoms (Red, Green, and Blue) RGB.
• The remaining colors are produced by the combination of Red, green, and blue.

 

b)     LCD (Liquid Crystal Display):

• It is thin and lightweight.
• They have better resolution and emit less radiation than CRT.
• They are portable, less expensive, reliable, and less harmful to the eyes than CRT.
• It has a fluid-like substance called liquid crystal between two sheets.
• These molecules are lined up on the screen and have two states.
• either they allow or block the light to produce images on the screen.
• They are used in, laptops, monitors, phones, clocks, etc.

c)      LED (Light Emitting Diode):

• It uses LED (Light Emitting Diode) as pixels.
• Lighter in weight and consumes less power than LCD.
• Better resolution and emit less radiation.
• Long-lasting and reliable.
• Expensive than other monitors

2.       Printers:

• Produce hardcopy output.
• Connected to computers through parallel or USB ports.
• Print quality, print speed, printing graphics.

 

Types of Printers:

1.       Impact printers

2. Non-impact printers

 

1.       Impact printers:

• Work like a typewriter.
• Image is produced when the print head strikes against the paper.
• Impact printers have low print quality
• they produce a lot of noise.
• They are slow and poor ability to print graphics.

Examples: Dot matrix and chain printers

 

2.       Dot matrix Printers:

• The dot matrix has 9 to 24 pins on its print head.
• Its print quality depends upon the number of pins.
• Not very popular nowadays.

   

3.       Chain printers:

• They are line printers. (can print one line at a time).
• It contains a character on a chain that moves very fast.
• The image is produced when a set of hammers strike against an ink ribbon on paper.

 

 

4.       Non-impact printers:

• They produce images without striking the paper.
• They are fast (print an entire page at a time).
• Better print quality than impact
• Produce very little noise while printing.
• Expensive than impact printers.
• Better ability to print graphics.

Examples: laser printers and inkjet printers.

 

 

5.       Laser printers:

• Print technology is similar to photocopiers.
• They are very fast and silent.
• Print an entire page at a time.
• Print quality is very high.
• Also, print colored graphics.

 

Inkjet printers:

• They produce images by spraying tiny drops of ink on paper.
• Less expensive and slower than laser printers.
• Print quality is also less than laser printers.
• Can produce colored prints cheaper than laser printers.

 

 

 

 

 

3.       Plotters:

• Produce large-scale hardcopy output.
• Used in architectural drawings, maps, graphs, civil engineering drawings, and panaflexes.

Examples: flatbed plotters and drum plotters.

 

1.       Flatbed plotters:

• Paper is spread and fixed on a rectangular flat surface.
• It has a mechanical arm holding different colored pens.
• Which is moved on the surface to draw the image.

2.       Drum Plotter:

• It has a rotating drum.
• The sheet is fed from one side of the drum.
• The drum rotates to move the paper.
• It produces large-size panaflexes.

 

3.       Speakers:

• Produce audio output.
• Attached to the sound card on the motherboard.
• Convers electric signals in sound form.

Speakers:

• Produce audio output.
  
• Attached to the sound card on the motherboard.
  
• Convers electric signals in sound form.

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