1. What is the system unit? 2. What are common components inside the system unit? 3. What is the motherboard? 4. What is a chip? 5. What are heat sinks and heat pipes? 6. What is memory?

1. The Components of the System Unit

2. What is the system unit?
p. 180 Fig. 4-1 Next
 Case that contains electronic
components of the computer used
to process data
 Sometimes called
the chassis

3. What are common components inside the system
unit?
p. 181 Fig. 4-2 Next
 Memory
 Adapter cards
 Sound card
 Modem card
 Video card
 Network card
 Ports
 Drive bays
 Power supply
power supply
ports
drive bays
processor
memory
sound card
video card
modem card
network card
 Processor

4. What is the motherboard?
p. 182 Fig. 4-3 Next
 Main circuit
board in system
unit
 Contains adapter
cards, processor
chips, and
memory chips
 Also called
system board
processor chip
adapter cards
memory chips
memory slots
motherboard
Expansion
slots for
adapter cards

5.  The main circuit board of a microcomputer.
The motherboard contains the connectors for
attaching additional boards. Typically, the
motherboard contains the CPU, BIOS, memory,
mass storage interfaces, serial and parallel
ports, expansion slots, and all the controllers
required to control standard peripheral devices,
such as the display screen, keyboard, and disk
drive.

6. What is a chip?
p. 182 Fig. 4-4 Next
dual inline
packages (DIP)
holds memory
chips
pin grid
array (PGA)
package
holds processor
chips
 Small piece of semi-conducting
material on which integrated
circuits are etched
 Integrated circuits contain
many microscopic pathways
capable of carrying electrical
current
 Chips are packaged so they can
be attached to a circuit board

7.  A small piece of semiconducting material
(usually silicon) on which an integrated circuit
is embedded There are different types of chips.
For example, CPU chips (also called
microprocessors)

8. Computer sockets are the built-in interfaces on motherboards
that accept various hardware components.

9. What are heat sinks and heat pipes?
p. 190 Fig. 4-11 Next
 Heat sink—component
that cools
processor
heat sink fan
heat sink
 Heat pipe—smaller
device for notebook
computers

10. Memory and
Storage
Next

11. What is memory?
p. 193 Fig. 4-17 Next
 Electronic components that
store instructions, data, and
results
 Consists of one or
more chips on
motherboard or
other circuit board
 Each byte stored
in unique location
called an address,
similar to seats
on a passenger train
Seat #2B4 Seat #2B3

12. 1.ROM (Read Only Memory)
2.RAM (Random Access Memory)
3.Cache
4.Flash memory

13.  There is a type of memory that stores data
without electrical current; it is the ROM (Read
Only Memory)
 or is sometimes called non-volatile memory as
it is not erased when the system is switched
off.

14.  PROM (Programmable Read Only Memory)
 EPROM (Erasable Programmable Read Only
Memory)
 EEPROM (Electrically Erasable Read Only
Memory .

15.  Programmable read-only memory (PROM) is a
blank ROM chip on which a programmer can
write permanently, but once written cannot
be changed or modified

16.  But most ROM chips designed to be modified
by users, use
 Erasable programmable read-only memory
( EPROM )
or electrically erasable programmable
read-only memory ( EEPROM ).

17. An EPROM or erasable programmable read
only memory, is a type of memory chip
Once programmed, an EPROM can be
erased

18.  EEPROM (Electrically Erasable Programmable
Read-Only Memory )is user-modifiable read-
only memory (ROM) that can be erased and
reprogrammed (written to) repeatedly

19. How is memory measured?
p. 194 Fig. 4-18 Next
Term Abbreviation Approximate Size
Kilobyte KB or K 1 thousand bytes
Megabyte MB 1 million bytes
Gigabyte GB 1 billion bytes
Terabyte TB 1 trillion bytes
 By number of bytes available for storage

20.  Random Access Memory, a type of computer
memory that can be accessed randomly; that is,
any byte of memory can be accessed without
touching the preceding bytes. RAM is the most
common type of memory found in computers and
other devices, such as printers.

21. What is random access memory (RAM)?
p. 195 Next
The more RAM a
computer has, the
faster it responds
Also called
main memory
or primary
storage
Most RAM is
volatile, it is lost
when computer’s
power is
turned off
Memory chips that can be
read from and written
to by processor

22. How do program instructions transfer in and out of RAM?
p. 195 Fig. 4-19 Next
Step 1. When you start the computer, certain
operating system files are loaded into RAM from
the hard disk. The operating system displays the
user interface on the screen.
Operating system
instructions
Web browser
instructions
Word processing
program instructions
Operating system
interface
Web browser
window
Word processing
program window
RAM
RAM
Web browser program
instructions are
removed from RAM
Web browser
window no longer is
displayed on
desktop
Step 2. When you start a Web browser, the
program’s instructions are loaded into RAM from
the hard disk. The Web browser window is
displayed on the screen.
Step 3. When you start a word processing
program, the program’s instructions are loaded
into RAM from the hard disk. The word
processing program, along with the Web Browser
and certain operating system instructions are in
RAM. The word processing program window is
displayed on the screen.
Step 4. When you quit a program, such as the
Web browser, its program instructions are
removed from RAM. The Web browser no longer
is displayed on the screen.

23. Faster
variations
of DRAM are
SDRAM and
RDRAM
Used for
special
applications
such as
cache
Most
common
type
Faster and
more reliable
than DRAM
chips
What are two basic types of RAM chips?
p. 196 Next
Static
RAM
(SRAM)
Dynamic
RAM
(DRAM)
Future: Magnetoresistive RAM (MRAM)

24.  There are two different types of RAM:
 DRAM (Dynamic Random Access Memory)
 SRAM (Static Random Access Memory).
 DRAM needs to be refreshed thousands of
times per second while
 SRAM does not need to be refreshed, which is
what makes it faster than DRAM. Both types of
RAM are volatile, meaning that they lose their
contents when the power is turned off.

25. Where does memory chips
reside?
p. 196 Fig. 4-20 Next
 Memory slots on
motherboard hold memory
modules
memory chip memory slot
dual inline memory module

26. What is read-only memory (ROM)?
p. 198 Next
Memory chips that store
permanent data
and instructions
Nonvolatile memory, it is not
lost when computer’s
power is turned off
Three types:
Firmware—
Manufactured with
permanently written
data, instructions,
or information
EEPROM
(electrically
erasable programmable
read-only memory)—
Type of PROM
containing microcode
programmer
can erase
PROM
(programmable
read-only
memory)—
Blank ROM
chip onto which
a programmer
can write permanently

27. What is cache?
p. 198 Fig. 4-23 Next
 Helps speed computer processes by storing frequently used
instructions and data
 Also called memory cache

28.  Non volatile memory can be erased
electronically and rewritten similar to EEPROM
 Most computers use it to hold up their
startup instructions
 Also used in many mobiles , smart phones ,
digital cameras and PDA

29.  The amount of time a processor takes to read
the data, instructions and information from
memory.
A computer’s access time affects how fast
the computer process data.

30. What is storage?
p. 348 Fig. 7-1 Next
 Holds data, instructions, and information for future use
 Storage medium is physical material used for storage
 Also called secondary storage

31. What is capacity?
p. 350 Next
Kilobyte (KB) 1 thousand
Megabyte (MB) 1 million
Gigabyte (GB) 1 billion
Terabyte (TB) 1 trillion
Petabyte (PB) 1 quadrillion
 Number of bytes (characters) a storage medium can hold
Exabyte (EB) 1 quintillion
Zettabyte (ZB) 1 sextillion
Yottabyte (YB) 1 septillion

32. Writing
Process of transferring
items from memory
to storage media
What is a storage device?
p. 350 Next
Reading
Process of transferring
items from storage
media to memory
Hardware that
records and
retrieves items
to and from
storage media
Functions as source
of input
Creates output

33. Floppy Disk Small files to be transported
Secondary Storage
Primary Storage
Hard Disk
CDs and DVDs
Miniature Storage Media
Tape
Items waiting to be interpreted
and executed by the processor
Operating system, application
software, user data and information
Software, backups, movies, music
Digital pictures or small files to
be transported
Backups
Memory (most RAM)
Stores …
What is access time?
p. 350
 Time it takes storage device to locate item on storage medium
Next
 Time required to deliver item from memory to processor
faster
transfer
rates
slower
transfer
rates

34. 1.floppy disk
2.Zip disk
3.Hard disk
4.CDs and DVDs
5.Tape
6.PC Card
7.Miniature mobile storage

35. What is a floppy disk?
p. 351 Fig. 7-5 Next
 Portable, inexpensive storage
medium (also called diskette)
Thin, circular, flexible film enclosed
in 3.5” wide plastic shell
shutter
shell
liner
magnetic
coating
flexible thin film
metal hub

36. What is a floppy disk drive?
p. 352 Fig. 7-6 Next
Floppy disk drive
built into
a desktop
computer
External floppy disk drive attaches to
a computer with a cable
 Also called secondary storage
 One floppy drive, named drive A
 If two floppy drives, second
designated as drive B
 Device that reads from and
writes to floppy disk

37. p. 354 Next
Never open the
shutter and
touch the disk’s
surface
How do you care for a floppy?
Avoid exposure
to heat and
cold Avoid exposure
to magnetic
fields
Avoid exposure
to contaminants
such as dust,
smoke, or
salt air
Keep disks in
a storage tray
when not
using them
 Proper care helps maximize disk’s life
 Floppy disk can last at least seven years

38. External
Zip drive
What is a Zip disk?
p. 355 Fig. 7-11 Next
 Magnetic medium that stores 100 MB
to 750 MB of data
 Zip disks require a Zip drivec—chigh
capacity drive that reads from and
writes on a Zip disk
 Used to back up and to transfer files
 Backup is duplicate of file, program, or disk
in case original is lost
c
Zip disk

39. What is a hard disk?
p. 355 Fig. 7-12 Next
hard disk installed
in system unit
 High-capacity storage
 Consists of several
inflexible, circular
platters that store items
electronically
 Components enclosed in
airtight, sealed case for
protection

40. What are characteristics of a hard disk?
p. 356 Fig. 7-13 Next
Sample Hard Disk Characteristics
Advertised capacity 120 GB
Platters 3
Read/write heads 6
Cylinders 16,383
Bytes per second 512
Sectors per track 63
Sectors per drive 234,441,648
Revolutions per minute 7,200
Transfer rate 133 MB per second
Access time 8.9 ms
actual
disk
capacity

41. How does a hard disk work?
p. 357 Fig. 7-14 Next
Step 1.
Circuit board controls
movement of head actuator
and a small motor.
Step 2.
Small motor spins
platters while
computer is running.
Step 3.
When software requests a
disk access, read/write
heads determine current
or new location of data.
Step 4.
Head actuator positions
read/write head arms over
correct location on platters
to read or write data.

42. What is a cylinder?
p. 357 Fig. 7-15 Next
 Vertical section of
track through all
platters
 Single movement
of read/write head
arms accesses all
platters
in cylinder
platter
read/write
head
platter
sides
cylinder
track
sector

43. What is a head crash?
p. 358 Fig. 7-16 Next
clearance
read/write head
platter
hair
dust
smoke
 Spinning creates cushion of air that floats read/write head above platter
 Occurs when read/write head touches platter surface
 A smoke particle, dust particle, or human hair could render drive unusable
 Clearance between head and platter is approximately two-millionths of an inch

44. hard disk
Next
What is a disk cache?
p. 358 Fig. 7-17
 Portion of
memory that
processor uses
to store
frequently
accessed items
second request
for data—to hard disk
disk cache
first request
for data—to disk cache
processor

45. What are external hard disks and removable hard disks?
p. 359 Fig. 7-18 Next
External hard disk—freestanding
hard disk that connects to system unit
Removable hard disk—hard disk
that you insert and remove
from hard disk drive
 Used to back up or transfer files

46. What is an Internet hard drive?
p. 360 Fig. 7-19 Next
 Others can be authorized
to access your data
 Service on Web that provides storage for
minimal monthly fee
 Files can be accessed from
any computer with Web
access
 Large files can be downloaded
instantaneously

47. Push the same button
to close the tray.
What are CDs and DVDs?
p. 361 Fig. 7-20 Next
 Most PCs include CD
or DVD drive, most
play audio CDs
 Flat, round, portable
metal discs made of
metal, plastic, and
lacquer
 Can be read only or
read/write
Insert the disc,
label side up.
Push the button to
slide out the tray.

48. How does a laser read data on a CD or DVD?
p. 362 Fig. 7-21 Next
laser
diode
laser
diode
prism prism
light-
sensing
diode
light-
sensing
diode
0 1
lens lens
pit land
disc label
Step 1.
Laser diode
shines a light
beam toward
disc.
Step 2.
If light strikes
a pit, it scatters.
If light strikes a
land, it is
reflected back
toward diode.
Step 3.
Reflected light is
deflected to a
light-sensing diode,
which sends digital
signals of 1 to
computer. Absence
of reflected light is
read as digital
signal of 0.

49. How is data stored on a CD or DVD?
p. 362 Fig. 7-22 Next
 Typically stored in
single track
 Track divided
into evenly
sized sectors
that store
items
single track
spirals to edge
of disc
disc sectors

50. What is a CD-ROM?
p. 363 Fig. 7-24 Next
 Compact disc read-
only memory
 Cannot erase or
modify contents
 Typically holds
650 MB to 1 GB
 Commonly used
to distribute
multimedia and
complex
software

51. What are CD-Rs and CD-RWs?
p. 366 Next
Must have
CD recorder
or CD-R drive
Cannot erase
disc’s contents
CD-R (compact disc-readable)
—cdisc you can write on once
CD-RW (compact disc-rewritable)
—ceerasable disc you can write on
multiple times
Must have
CD-RW software
and CD-RW drive

52. What is tape?
p. 370 Fig. 7-29 Next
 Magnetically coated plastic ribbon
capable of storing large amounts
of data at low cost
 Primarily used for backup

53. How is data stored on a tape?
p. 370 Fig. 7-30 Next
 Sequential access
 Unlike direct access — used on floppy disks, Zip disks,
hard disks, CDs, and DVDs — which can locate
particular item immediately
 Reads and writes data consecutively, like music tape

54. What is a PC Card?
p. 370 Figs. 7-31–7-32 Next
PC Cards
Category Thickness Use
Type I 3.3 mm RAM, SRAM, flash
memory
Type II 5.0 mm Modem, LAN, SCSI,
sound, TV turner, hard
disk, or other storage
Type III 10.5 mm Rotating storage such
as a hard disk
 Adds capabilities to computer
 Credit-card-sized device commonly
used in notebook computers

55. What is Miniature mobile storage media?
p. 371 Fig. 7-33 Next
 Storage for small mobile devices

56. What are common types of miniature mobile storage media?
p. 372 Next
Smart Media
xD Picture Card
CompactFlash Secure Digital
Memory Stick Microdrive

57. What is a card reader?
p. 373 Fig. 7-35 Next
 Reads information stored on miniature mobile storage media
 Type of card determines type of card reader needed

58. What is a smart card?
p. 373 Fig. 7-37 Next
 Stores data on microprocessor
embedded in small card
 Input, process, output, and
storage capabilities

59. What are microfilm and microfiche?
p. 374 Fig. 7-38 Next
Images recorded using
computer output microfilm recorder
Store microscopic images of
documents on roll or sheet of film
Microfilm — 100- to
215-foot roll of film
Microfiche — small sheet
of film, usually 4”  6”

60. A metaphor……….
The file cabinet represents the computer's
hard disk, which provides storage for all the
files and information you need in your office.
When you come in to work, you take out the
files you need from storage and put them on
your desk for easy access while you work on
them. The desk is like memory in the
computer: it holds the information and data
you need to have handy while you're working.

61. The two terms are sometimes used
interchangeably, so it is important to
understand some key differences.
1. The term memory refers to the amount of
RAM installed in the computer, whereas the
term storage refers to the capacity of the
computer’s hard disk.

62. 2. Both terms are used to refer to internal
storage space on a computer. Memory,
usually referred to as Random Access Memory
(RAM), is the place where an application loads
its data during processing, while a hard disk
drive is usually the place where data is stored
for long or short term retention.

63. 3. Memory dumps everything when you turn
off your computer, in nature but the hard
drive retains what is stored on it.
4. Memory is typically volatile Storage is
typically non-volatile .
5. Memory is quite a lot faster than hard
drive.
6.Computer storage is typically cheaper,
slower while computer memory is expensive
and faster

64. Storage Medium
(floppy disks, Zip disks,
hard disks, CDs)
How does volatility compare?
p. 350 Next
Nonvolatile
 Storage medium is nonvolatile—contents retained when
power is off
Contents
retained
Contents
available to user
Memory
(most RAM)
(chips on motherboard)
Screen Display
ON OFF
Volatile
Display
disappears
Data and
instructions
available to user
Display
appears
Data and
instructions erased
 Memory is volatile—holds data and instructions temporarily