The document provides an overview of computer systems and their components. It discusses that a computer system consists of computer hardware and software, with each subsystem performing unique tasks. The main components of hardware include the input devices, output devices, central processing unit, storage devices, and motherboard. Input devices allow data to enter the system, like keyboards, mice, and scanners. Output devices allow data to leave the system, like monitors, printers, and speakers. The CPU controls the functioning of the computer and includes control units and arithmetic logic units. Storage devices temporarily or permanently store data and include RAM, ROM, hard drives, flash drives, and optical disks. The motherboard serves as the main circuit board that connects these components.

1. Chapter 2
Computer Systems
1
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2. Introduction
 Computer System: is a combination
of computer hardware and computer
software where each subsystem has
their own unique task to perform to
achieve the goal of computer.
 Components of a Computer System
A. Computer Hardware
B. Computer Software
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3. 2.1 Computer Hardware
 Computer hardware is the physical
part of the computer that you see, the
parts you can touch.
 In short , the tangible part of a
computer.
 Basic units of Computer Hardware
◦ Input Devices
◦ Output Devices
◦ Central Processing Unit (CPU)
◦ Storage Devices
◦ MotherBoard
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4. Hardware
•System Unit
•Peripheral Devices
System Unit
Peripheral Devices
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5. You must Know this parts!
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6. Basic Architecture of Computer Hardware
CPU
CU ALU
RAM
INPUT
DEVICE
OUTPUT
DEVICE
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7. Bus
 The communication b/n hardware is
done using the bus.( Arrows in the
above fig).
 It serves as road between the
hardware parts.
 Three types of bus to communicate
with CPU.
◦ Data Bus: to exchange data back and
forth
◦ Address Bus: to exchange location info
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8. Buses: The CPU’s Data Highway
 Bus
–Electrical pathway used to move data
between components.
– Local bus: Connects the CPU with the memory.
– Expansion bus: Connects the CPU with peripheral
devices.
01100010
01110011
01001000
00100111
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9. 2.1.1 Input devices
 Input devices are used to enter data
into computer.
◦ The data may be text, audio, video,
Image..etc.
 There are different kinds of input
devices, but the most frequently used
input devices are keyboard and
mouse.
 Others...Scanner, Microphone,
Camera, joy stick, touch screen.....etc.
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10. Keyboard
 It is a simple computer input device
comprising a set of alphabetic,
numeric, punctuation symbol, control,
and function keys mounted on a board
or other flat surface or control panel.
 When the user depresses a key or a
combination of keys, a coded signal is
sent to the computer.
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11. Keyboard…
 The keys on the keyboard are often
classified as follows:
◦ Alphanumeric keys - Letters and
numbers.
◦ Punctuation keys - comma, period,
semicolon, etc.
◦ Special keys- function keys, control
keys, arrow keys, caps lock, etc.
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12. Keyboard…
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13. QWERTY Keyboard
 The QWERTY keyboard with enhanced
features is standard with most modern
personal computers.
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14. Dvorak Keyboard
 Puts the most commonly used keys at “home ke
 Reduces distance of finger stretches
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15. Specialty Keyboards
• Laptops
• PDAs
• Wireless
• Ergonomic
Laptop
Ergonomic
PDA
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16. Mouse
 It is a device that controls the
movement of the cursor or pointer
on a display screen.
 Mouse can have as many as three buttons
whose function depends on what program
is running:
◦ Left-button: for left click. Example,
selecting text
◦ Right-button: for right click. Example,
see property of file
◦ Middle button: for scrolling purpose.
This button is sometimes missing.
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17. Mouse…
 Mouse components
◦ Left (primary ) & Right
(secondary)
 Mouse events/
mouse Operations
◦ Left click
◦ Right click
◦ Drag and Drop
◦ Single and
Double click
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18. Types of Mouse
 Roller ball mouse
– Less expensive
– Harder to keep clean
 Trackball
– Harder to control
– Stationary on desk
 Optical mouse
– Needs no mouse pad
– Doesn’t need cleaning
– More expensive
Wireless
Optical
Trackball
Standard
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19. Other Input Devices
• Scanners
– Text
– Images
• Digital cameras
– Images
– Video
Flatbed
Handheld
Camera Camcorder
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20. Scanner
 Scanners will convert image on paper
to a digital data that can be
manipulated by the computer.
 Scanning the images with light and
breaking them into matrix of dots.
Each dot will have a digital code. The
dots are sometimes referred as pixels.
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21. Input Devices…
 Microphones could be used to enter
sound data.
 Camera could be used to capture
image and video data.
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22. 2.1.2. Output Devices
 Output devices are used to get data
out of a computer so that it can be
examined, analyzed or distributed to
others.
 It converts information from machine-
understandable form to a human
understandable form.
 Outputs are of two types:
◦ Softcopy: displayed on monitor, projector
◦ Hardcopy: printed on paper
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23. Output Devices...
 The Visual Display Unit (VDU)
◦ or monitor or screen
 Printers
◦ dot matrix, daisy wheel, laser printers
 Plotters
 Voice (audio) response unit
◦ Speaker, headphone
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24. Monitors
 Monitor is the most frequent type of
output device.
 Image is displayed on monitors using
pattern of lighted dots.
 Each of these lighted dots is called
pixel.
 There are three types of monitor:
◦ CRT (Cathode Ray Tube)
◦ LCD (Liquid Crystal Display)
◦ GPD (Gas Plasma display )
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25. Monitor Types
 CRT Cathode Ray Tube
– Less Expensive
– Use much more space
– Uses more energy
– Better viewing angles
 LCD Liquid Crystal Display
– More expensive
– Uses for less space
– More energy efficient
– Less viewable from an angle
GPD Gas Plasma Display
– The most Expensive
– Uses neon gas
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26. Output devices…
Printers
 Printer is a device that enables us to
produce a hardcopy of
data/information.
 Based on the way they print, printers
are divided into two:
◦ Impact printers
◦ Non-impact printer
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27. Printers…
Impact printers
 Impact printers transfer printable material onto
paper by striking paper, ribbon, and character
together.
 Most of such printers take continuous form of
paper.
 The most commonly used impact printers are
dot-matrix printers.
Non-Impact Printers
 They print without having a mechanism that
strikes a paper.
 They print by spraying ink or by using heat and
pressure to fuse colour powder onto paper.
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28. Printers
 Impact printers
– Dot-matrix
 Non-impact
printers
– Inkjet
– Laser
– Multifunction
 Specialty printers
– Plotters
– Thermal printers
Dot-matrix
Inkjet
Multifunction
Laser
Plotter
Thermal printer
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29. Non-impact Printers
 Ink Jet
– Less expensive device
– Full color printing
– Slower in pages per minute
(PPM)
– More expensive per page in
B&W
 Laser
– More expensive device
– Black and White (Color lasers
are very expensive)
– Faster in PPM
– Less expensive in B&W
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30. Output devices…
 Plotters
 Plotters are used to produce high-
quality drawings such as bar charts,
maps, architectural drawings, and
three-dimensional drawings.
◦ Can print on large size papers, which
most printers can’t handle.
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31. Outputting Sound
 Speakers and
Headphones
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32. Speaker
 Audio sound files input into multimedia
PC through a microphone. Then you
can here the output through speakers.
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33. 2.1.3. Central Processing Unit
 CPU is responsible for interpreting and
executing most of the commands from the
computer's hardware and software.
 It is often called the "brain" of the computer.
 Controls all functions of the computer.
 Component of CPU
◦ Control unit: it is responsible to Move data and
instructions between main memory and registers.
◦ Arithmetic logic unit (ALU): it responsible to
performs computation and comparison
operations.
◦ Set of registers: it is responsible to storage
locations that hold inputs and outputs for the
ALU. 1 33

34. CPU…
 Fig Shows Components of Central
Processing Unit
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35.  Store data and programs
2.1.4. Storage devices
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36. Primary storage devices
 Is directly accessible to the CPU
 To store data that is likely to be in
active use.
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37. RAM
 Random access memory
 Volatile: When you turn off your computer, the
data is erased
 Several kinds of RAM exist
 Each type of RAM has a different design
– Some types work at much faster speeds
– Some transfer data more quickly
 Stores instructions and data
 Temporary (volatile) storage
 Operates in nanoseconds
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38. ROM
 Read only memory (ROM)
 Stores data and programs that are permanently
required by the computer.
 Non-volatile.
 Read only-contents cannot be changed.
 The technological advancement in ROM design
has resulted in three other types of ROM:
◦ PROM (Programmable ROM)
◦ EPROM (Erasable Programmable ROM)
◦ EEPROM (Electrically Erasable Programmable
ROM) 1 38

39. Secondary storage devices
 Not directly accessible by the CPU
 To store data that is not in active use
 Slower than primary storage devices
 Higher storage capacity
 Non-volatile
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40. Hard Disk Drive
• Stores data and program
instructions
• Permanent (nonvolatile)
storage
• Storage capacities up to 250
GB and higher
• Transfers data in
milliseconds
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41. Flash Disks
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42. Floppy disk
 Floppy disk(diskette):
 Magnetic storage medium used with
computers.
 Floppy disks are made of flexible
plastic coated with a magnetic
material, and are enclosed in a hard
plastic case.
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43. Floppy disk…
 31/2 inch: -can store 1.44MB of data
 51/4 inch: -can store 1.2MB of data
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44. Optical Disks
 Use laser light to read or write data
 DVD, CD
 CD (compact disc)
◦ Can store up to 700 MB
◦ Three types
 CD-ROM( compact disk read only memory)
 You can’t write to or erase
 CD-R (compact disk recordable)
 Can be written on once but can’t be erased-
WORM (write once read many)
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45.  CD-RW –(compact disk rewritable)
 Can write several times
 Can be erased
 DVD- Digital Versatile Disc
 Can store 4GB, 8GB,17GB,…
Optical Disks…
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46. 2.1.5. Overview of motherboard
 The motherboard is the main circuit board inside your
PC. Every component at some point communicates
through the motherboard, either by directly plugging into
it or by communicating through one of the
motherboards ports.
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47. Ports and Connectors
Serial ports:
 Transmits or receives data one
bit at a time.
 They are very good to send
information over long distance.
 Devices like
◦ keyboard, mouse, modem,
and etc. use serial ports to
connect to system unit of
computer.
Parallel ports:
 Transfer and receive multiple
bits of information at a time.
 They are used for short
distance communication.
 Devices such as
◦ printers, disk drives, tape
drives, and etc. used
parallel ports.
Parallel port (Printer port)
• A port is a socket used to connect the
peripheral devices to system unit.
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48. Power Supply Unit (PSU)
• Supplies DC power to the other components in a
computer.
• It converts general-purpose alternating current (AC)
electric power from the mains to low-voltage direct
current (DC) power for the internal components of the
computer.
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49. Expansion Cards
• Adds functions
• Provides new connections for peripheral
devices
• Common types:
– Sound
– Modem
– Video (VGA)
– Network (NIC)
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50. Any Question?