11th Class (HSSC-I) Computer SLO Based Key Point Notes
************************************👉👉👉Computer Science 11th Class Notes (Main Page)
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Unit-1
"Introduction to Computers"
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.
- Supercomputers
- Mainframe computer
- Mini computers
- 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:
- System software
- Application
software
- Internet applications
- 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:
- Operating system
- Device drivers
- Utility software
- 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:
- Productivity
software.
- Business
software.
- Entertainment
software.
- 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:
- Web applications
- Cloud computing
applications
- 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.
************************************👉👉👉Computer Science 11th Class Notes (Main Page)
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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:
- Size: The monitor
varies in size from 15 to 21 inches.
- Colour: monitor can be
black and white or RGB (colored).
- Pixel: stands for
picture element. It is a small dot on the monitor forming an image.
- Resolution: numbers of
pixels per square inch. The higher the resolution better the image
quality.
- 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
- 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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