Topics of Discussion

1
Topics of Discussion

• Storage devices.
• Magnetic storage

2
Storage

• Storage refers to the media on which data,
  instructions and information are kept.

3
Storage

• Storage is different from memory.

4
Memory

• Chips on motherboard or other boards.
• Memory temporally holds data and instructions
  during processing.
• Also called primary storage.

5
Memory

• Two types of memory
• Volatile losses data if the power is off eg
  RAM
• Non volatile does not lose its contents when
  power is off- eg. ROM chip

6
(No Transcript)
7
Storage

• Storage medium is the physical material on which
  data is kept, e.g. disk.
• Storage device is the mechanical apparatus that
  records and retrieves the data from the storage
  medium.

8
Storage

• Also called
• secondary storage.
• Auxiliary storage
• Permanent storage
• Mass storage

9
Storage

• Storage is no-volatile
• Contents are kept until the medium is damaged

10
Storage

• The process of storing data is referred to as
  writing data or saving a file.
• The process of retrieving data is referred to as
  reading data or opening a file.

11
Storage Specifications

• Access time
• Time it takes a computer to locate data on the
  storage medium and read it.
• Usually measured in milliseconds (1000th of a
  second).

12
Storage Specifications

• Storage capacity
• Maximum amount of data that can be stored on a
  storage medium.
• Kilobyte 1024 bytes (1000)
• Megabyte 1048576 bytes (1 million)
• Gigabyte 1073741824 bytes (1 billion)

13

14
Magnetic Storage

• Computer stores data on disks or tape by
  magnetizing selected particles of an oxide-based
  surface coating.
• The particles retain their magnetic orientation
  until that orientation is changed, thereby making
  this media fairly permanent but modifiable.

15
Magnetic Storage

• Common types
• Floppy disk
• Hard disk

16
Floppy Disk

• Is a round piece of flexible Mylar plastic
  covered with a thin layer of magnetic oxide.
• Sealed inside a hard protective plastic casing.
• Sometimes incorrectly called stiffy disks
  because of their hard casing.

17
(No Transcript)
18
Floppy Disk

• Introduced by IBM in 1970
• Original size was 8-inches wide
• Current size is 3.5-inches wide

19
Floppy Disk

• Must be formatted before data can be stored on
  the disk.
• Formatting organizes the disk into storage
  locations called tracks and sectors.
• Sectors (2 to 8) are grouped into clusters for
  reading/writing purposes.
• Cluster is the smallest unit of space used to
  store data.

20
(No Transcript)
21
Floppy Disk

• Typically stores data on both sides and has 80
  tracks on each side with 18 sectors per track.
• Commonest floppy disk is 3½ inch and store
  approximately 1.44 MB.
• Can be protected from accidental erasure by using
  the write-protect notch.

22
(No Transcript)
23
File Allocation Table

• Formatting also define the FAT, which is a table
  of information used to locate data on a disk.
• Maintains a list of files and their physical
  location on the disk.
• Crucial file that if corrupted will result in the
  loss of access to your data.
• Erasing data simply changes the FAT to indicate
  an empty cluster. The physical data is not
  removed.

24
Floppy Disk Drives (FDD)

• Used to read and write on a floppy disk.
• Usually designated the A drive.
• Some systems will have two FDDs and the second
  one will be B drive
• Light on the front of the drive indicates the
  drive is accessing a floppy disk.
• NEVER remove a floppy disk if this light is on.

25
Floppy Disk Drives (FDD)

• Normally installed inside the system unit
• Some notebooks have a removable floppy disk drive

26
Higher density disk

• A disk with higher density has more bits in an
  area- larger storage capacity
• Used as backup disk (duplicate)
• HD floppy disk drive to read/write
• Used for disks with - 100 MB
• Can read/write large amount of data.

27
Floppy Disk Drives (FDD)

• Downward compatible can recognise and use
  earlier media.
• Upward compatible cannot recognize newer media.
• NB Lower-density floppy disk drive cannot read
  from or write on a high-density floppy disk.

28
HD floppy disk drives

• Types -
• Super disk
• tm
• HiFD
• Zip

29
(No Transcript)
30
Disk Care