Class 11 Computer Science (SLO Based) Notes For the Examination 2023-2024 and onwards under the Federal Board of Intermediate and Secondary Education (FBISE), Islamabad, Punjab Boards, Rawalpindi, Lahore, Karachi Board, and All other boards in Pakistan and abroad. (Contact WhatsApp # 03339719149 for full book PDF Notes)
Unit-1
"Introduction to Computers"
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Brief/Long Response Questions and Answers:
Q3. What is Computer Hardware? Explain in detail.
Ans:
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. TouchPad:
- 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
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.
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