Comp App Lect 4.pptx

1. Secondary storage Devices
A secondary storage device refers to any non-volatile storage
device that is internal or external to the computer. It can be any storage
device beyond the primary storage that enables permanent data
storage. A secondary storage device is also known as an
auxiliary storage device or external storage.

3. Storage
• Store information
• Storage involve two processes:
• Writing or recording the data so it can be found later for use,
• Reading the store data, then transferring it into the computers
memory.

4. Storage
• The physical materials on which data is stored are called storage
media. E.g., diskette.
• The hardware components that write data to, and read data from,
storage media are called storage devices. e.g., diskette drive.

5. Store Information
• A storage device is a hardware device designed to
store information. There are two types of storage
devices used in computers; a 'primary storage'
device and a 'secondary storage' device.
Primary storage Secondary storage

6. Storage Devices
p. 354 Fig. 7-1 Next
 Storage devices are used to data and programs permanently
 These devices are used to store large volume of data and program
 Also called backing storage devices ,secondary storage devices,
or auxiliary devices

7. Storage Medium
(floppy disks,
hard disks, CDs)
•How does volatility compare?
p. 356 Next
Nonvolatile
 Storage medium is nonvolatile—contents retained when
power is off
Contents
retained
Contents available
to user
Memory
(most RAM)
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

8. Types of Storage Media
Magnetic Disk
Optical Disc

9. Magnetic Disk
It is most widely used storage media.
A magnetic disk is a thin, circular metallic plate coated with magnetic material.
Information can be recorded on or read from the magnetic surface
Following are the types of Magnetic Disks:
1.Floppy Disk
2.Hard Disk

10. Magnetic Disks
• What is a floppy disk?
 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

11. • What is a floppy disk drive?
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
 Device that reads from and
writes to floppy disk

12. • What is a write-protect notch?
Next
 Small opening with a cover that you slide
 Protects floppy disk from being erased accidentally
write-protected
not write-protected
notch closed
means you
can write on
the disk
notch open
means you
cannot write
on the disk

13. • What is a hard disk?
Next
hard disk installed
in system unit
 High-capacity storage
 Consists of several
inflexible, circular plate
that store items
electronically
 Components enclosed in
airtight, sealed case for
protection

14. • Characteristics of Hard Disk:
Some important characteristics of Hard Disk are as follows:
It provides large storage capacity
The capacity of computer hard disk is from 2 to 80 GB and more
It is much faster than Floppy Disks
It is primary media for storing data and programs
It is more reliable than floppy disk
Data stored on hard disk is safer than floppy disk

15. Push the same
button
to close the tray.
Optical Discs
• What are optical discs?
Next
 Most PCs include an
optical disc drive
 Flat, round, portable metal
discs made of metal, plastic
 Optical disk uses laser
technology to read and
write data
 Can be read only or
read/write
 Optical disk storage
capacity is from 600 MB to
over 1 GB
 It is much safer than
magnetic media
Insert the disc,
label side up.
Push the button to
slide out the tray.

16. Optical Discs
• How should you care for an optical disc?
p. 368 Fig. 7-22 Next
Do store the
disc in a jewel
box when
not in use
Do hold a disc
by its edges
Do not
eat, smoke, or
drink near
a disc
Do not stack discs
Do not expose
the disc to
excessive
heat or
sunlight
Do not touch
the underside
of the disc

17. Optical Discs
• Categories of Optical disks:
1.CD
2.DVD
• CD:
 Stands for Compact Disk
 It is most widely used media today
 A single CD can store from 650 MB to 1 GB
 The contents of CD can be read by CD drive
Different types of CDs are as follows:
1. CD-ROM
2. CD-R
3. CD-RW

18. • What is a CD-ROM?
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

19. • What are CD-Rs and CD-RWs?
Next
Must have
CD recorder
or CD-R drive
Cannot erase
disc’s contents
CD-R (compact disc-recordable)
—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

20. •Digital Video Disk (DVD)
It is similar to CD-ROM
It uses laser beams
Its storage capacity is much greater
than CD-ROM
It can store up to 17 GB of data
Next
 High capacity disc capable of
storing 4.7 GB to 17 GB
 Must have DVD-ROM drive or
DVD player to read DVD-ROM
 Stores databases, music,
complex software, and movies

21. Optical Discs
1.DVD-R
– Stands for Digital Video Disk Recordable
– It is similar to CD-R
– The user write data on DVD-R only once but can read many times
– The data written on it cannot be erased
2.DVD-RW
– it stands for Digital Video Disk rewritable
– The user can write data on it many times by erasing the existing contents