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IGCSE Information and Communication Technology

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Chapter 3 Storage devices and media Code Subject: 9713 In this chapter Back up Type of access Backing storage media Fixed hard disk Portable hard disk Floppy disk ... – PowerPoint PPT presentation

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Title: IGCSE Information and Communication Technology


1
IGCSE Information and Communication Technology
Chapter 3 Storage devices and media
  • Code Subject 9713

2
In this chapter
  • Back up
  • Type of access
  • Backing storage media
  • Fixed hard disk
  • Portable hard disk
  • Floppy disk drives
  • Magnetic tapes
  • Optical storage media
  • CD ROM DVD ROM
  • CD RW DVD RW
  • DVD RAM
  • Blu-ray disk
  • Solid state backing store
  • Memory sticks/pen drives
  • Flash Memory Cards

3
Back up
  • In computers, backup storage is storage that is
    intended as a copy of the storage that is
    actively in use so that, if the storage medium
    such as a hard disk fails and data is lost on
    that medium, it can be recovered from the copy.
    In an enterprise, because the loss of business
    data can be catastrophic, it is important that
    backup storage be provided.
  • Data selected, extracted and manipulated before
    backuping
  • Data security
  • Data repositories

4
Why backup data?
  • Data could be lost because of hardware failure
  • Hackers could be responsible for the corruption
    of data
  • Backups made in case the data need to be used
    elsewhere
  • Virus can effect our data
  • Backup storage must be protected form virus

5
Type of Access
The way data is store and read by different
backing storage devices
  • Serial Access
  • Direct Access
  • Start at the beginning until require information
    found
  • Used on magnetic tapes
  • Very slow
  • In update need to used additional magnetic tape
  • Magnetic and optical disk
  • Use a key to calculate where the data has been
    store
  • Access the data directly
  • Used in application with real time process
  • When updating the data store in next available
    location calculated by an algorithm

6
Backing storage media
  • All computer systems have some equipped with some
    form of backing storage
  • RAM data is stored temporarily
  • Backing storage devices ensure that data is store
    permanently
  • Backing storage devices can be internal or
    external
  • Three types
  • Magnetic
  • Optical
  • Solid state

7
Fixed Hard Disk
  • All computers have HDD
  • Main method to store data
  • Data store using 1s and 0s
  • Operating system and other important files
  • Application software need hard drive to save and
    retrieve data

8
Fixes Hard Disk
  • Uses
  • Store operating system and data
  • Application software
  • Real time systems (e.g. robots, online systems,
    stock control, EPOS)
  • Used in file servers
  • Advantages
  • Very fast date transfer
  • Large amount of memory
  • Disadvantages
  • Can be easy damaged
  • Lack portability

9
Portable hard disk drives
  • Similar to fixed hard drives
  • Connected to the computer via universal serial
    bus (USB)
  • Store more data than optical disk
  • Uses
  • Used to back up systems
  • Transfer data, files and software between
    computers
  • Advantages
  • Access time is very fast
  • Transfer rate is very fast
  • Can be used as method of transferring information
    between computers
  • Disadvantages
  • Can be easily damaged

10
Floppy disk drives
  • Thin disk of plastic which is housed in a plastic
    case with a windows where the disk can be
    accessed
  • Floppy disks are read and written by a floppy
    disk drive or FDD
  • Uses
  • Small files need to be transfer
  • Older computers still use this devices as storage
  • Advantages
  • Use CD for small files is wasteful
  • Low cost and very simple technology

11
Floppy disk drives
  • Disadvantages
  • Very low memory capacity
  • Most of the Modern computers avoid to use this
    type of media storage
  • Data transfer rate is slow
  • Floppy disks are not very robust

12
Magnetic Tapes
  • Magnetic tape is a very thin strip
  • Read and Write
  • Date is stored in magnetic areas represents 1s
    and 0s
  • Data read and written in sequence
  • Serial access method
  • Patch processing

13
Magnetic Tapes
  • Uses
  • Used as a backup media since all the data needs
    to be stored
  • Used in applications required patch processing
  • Advantages
  • Less expensive
  • Very robust technology
  • Transfer rate is fast
  • Disadvantages
  • Access time is very slow
  • Need another tape in update

14
Optical storage devices
  • Use optical light read/write methods
  • A laser beam is used to read and write
  • Single or two polycarbonate disk
  • Very thin layer
  • Portable and large amount of storage space
  • Films, music, multimedia files

15
CD-ROM and DVD-ROM
  • Read Only Memory (ROM)
  • Data is stored as a series of pits and lands
  • 1 and 0
  • Spirals out of the centre of the disk
  • Read from the center outwards in a spiral
  • 1s and 0s, light reflects differently

16
CD-ROM and DVD-ROM
  • Uses
  • Store music files
  • Software computer games and reference software
  • DVD ROMs have much larger storage capacity than
    CDs
  • CDs are used to store computer data and software
  • Advantages
  • Hold more data then floppy
  • Less expensive than hard drive
  • Disadvantages
  • Slower data transfer and access rate then hard
    drive

17
Blu-Ray Disk
  • Largest capacity, up to 100GB
  • Blue laser beam
  • Shorter wavelength, more date can be stored
  • Uses
  • Home video
  • Store and playing back films, 25 GB two hours
    duration
  • Data storage, backing up HDD
  • Camcorders can use the media to store film

18
Blu-Ray Disk
  • Advantages
  • Very large storage capacity
  • Transfer rate is very fast
  • Data access speed is also grater than other
    optical media
  • Disadvantages
  • Expensive
  • Encryption problems in case of video

19
Solid state backing store
  • Solid state drives will replace the laptop HDD
  • Faster data access time
  • Extremely robust
  • Data is still stored 1s and 0s
  • Instead of thin rotated disk, these systems
    control the movement of electrons within the
    microchips
  • Less power
  • Removable storage

20
Memory stick/pen drives
  • Connected to the computer vie USB(universal
    serial bus)
  • Can store sever GB
  • Very portable
  • No additional software need
  • Uses
  • Transporting files between computers
  • Back up store
  • Security device

21
Memory stick/pen drives
  • Advantages
  • Very compact and portable media
  • Very robust
  • Disadvantages
  • Not possible to write protect data
  • Easy to lose

22
Flash memory cards
  • Electrical erasable programmable read only memory
  • Uses
  • Store photos on digital cameras
  • Mobile phones
  • MP3 players
  • Backup store in handheld computer devices
  • Advantages
  • Very compact
  • Very robust
  • Disadvantages
  • Expensive per GB
  • Finite life
  • Lower storage capacity

23
Storage Capacity
  • An important characteristic of any storage device
    is its capacity or how much data it can store.
    This is measured in bytes. One byte is one
    characters worth of storage, so the number of
    bytes of storage space is a measure of how many
    characters worth of data the device can hold, ie
  • 1 byte 1 character
  • 1 kilobyte 1024 bytes (210)
  • 1 megabyte 1024 kilobytes 1 048 576 bytes
    (220)
  • approximately 1 million bytes
  • 1 gigabyte 1024 megabytes 1 073 741 824 bytes
    (230)
  • approximately 1 thousand million bytes
  • 1 terabyte 1024 gigabytes 1 099 511 627 776
    bytes (240)
  • approximately 1 million millions bytes
  • Note that kilo (1024) is not the same as the
    normal kilo (1000). 1024 is 210 which is more
    useful because of the way in which computers
    handle data.

24
Key Points
  • Backing storage holds the data that the computer
    does not currently need.
  • Data that is currently being processed is held in
    memory.
  • Backing storage is either magnetic or optical.
  • Memory chips are either RAM or ROM.
  • RAM is volatile memory, ROM is non-volatile.
  • Disk storage allows direct or sequential access,
    tape storage only sequential.
  • CD storage is suitable for reference material and
    software installations.
  • DVD storage is suitable for video, large
    encyclopedias, very large amounts of data and
    back-up.

25
Key Points
26
Review Questions
  • What type of backing storage would be most
    suitable for each of the following situations? In
    each case give a reason for your answer.
  • Taking a spreadsheet file home to carry on
    working on it.
  • Storing details of customers and parts for a
    local garage.
  • Backing-up the hard disk of a home computer.
  • Distributing computer training materials that
    include about 90 minutes of video.
  • Distributing a parts catalogue consisting of
    about 200 MB of data to many thousands of
    customers.
  • What do ROM, RAM, hard and floppy disks, magnetic
    tape and optical discs all have in common?

27
Review Questions
  • What do ROM, RAM, hard and floppy disks, magnetic
    tape and optical discs all have in common?
  • ROM and RAM chips make up the computers memory.
    The data stored in a ROM chip is put in when the
    chip is manufactured. It is never lost and it
    cannot be changed. The data stored in a RAM chip
    can be changed and it is lost when the power is
    turned off.
  • Which type of memory chip stores the computer
    program that runs when the
  • computer is first turned on? Give a reason for
    your answer.
  • Which type of memory chip stores a document while
    it is being word-processed?
  • When a word-processed document is completed, it
    is saved to a hard disk drive.
  • Give two reasons why the hard disk drive is
    needed.

28
Review Questions
  • A random access medium allows data to be
    recovered in any order. Only one of the media
    mentioned in Question 1 does not allow random
    access. Which one is it?
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