1. Lecture # 5
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2.  Storage devices hold data, even when the computer
is turned off.
 The physical material that actually holds data is
called a storage medium. The surface of a floppy
disk is a storage medium.
 The hardware that writes data to or reads data from
a storage medium is called a storage device. A
floppy disk drive is a storage device.
 The two primary storage technologies are magnetic
and optical.
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4.  Surface of magnetic Disks and tapes are
coated with millions of tiny iron particles so
that data can be stored on them
 Read/Write heads of a magnetic disk or tape
drive contains electromagnets that generate
magnetic fields in the iron on the storage
medium as the head passes over the disk
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5.  A storage device is the computer hardware
that records and/or retrieves items to and
from storage media
Reading is the process
of transferring items
from a storage medium
into memory
Writing is the process of
transferring items from
memory to a storage
medium
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6.  Access time measures:
 The amount of time it
takes a storage device
to locate an item on a
storage medium
 The time required to
deliver an item from
memory to the
processor
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7.  Formatting is the process of dividing the disk into tracks
and sectors so that the operating system can store and
locate data and information on the disk
 Before a magnetic disk can be used, it must be formatted—
a process that maps the disk's surface and determines how
data will be stored.
 During formatting, the drive creates circular tracks around
the disk's surface, then divides each track into sectors.
 The OS organizes sectors into groups, called clusters, then
tracks each file's location according to the clusters it
occupies.
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8.  Boot sector
 File allocation Table (FAT)
 Root folder
 Data Area
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9.  Tracks-
 circular areas of the disk
 Length of a track one circumference of disk
 Over 1000 on a hard disk
 Data first written to outer most track
 Sectors-
 Divides tracks sections
 On a floppy 9 sectors exits
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10.  Cylinders-
 Logical groupings of the the same track on
each disk surface in a disk unit
 Clusters-
 Groups of sectors used by operating system
 64 sectors in one cluster
 Partitioning: divide hard disk into separate areas
called partitions; each partition functions as if it
were a separate hard disk drive.
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11.  File Allocation Table(FAT)
 FAT32
 New Technology file system (NTFS)
 NTFS 5
 High performance File System (HPFS)
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12.  Uses magnetic storage technology
 Has read / write heads
 Includes a motor that rotates the disk on a
spindle and read/ write head that can move to
any spot on the disk’s surface as the disk spins
 Disk Density- the amount of data that a disk can
hold
 To determine disk density multiply its total
number of sectors by the number of bytes each
sector can hold
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13.  Hard disks can store data
using longitudinal recording
or perpendicular recording
 Includes one or more platters
mounted on a central spindle
 Each platter is covered with a
magnetic coating
 It includes motor to spin
platters and read/write heads
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15.  An external hard disk is a separate free-
standing hard disk that connects to your
computer with a cable or wirelessly
 A removable hard disk is a hard disk that you
insert and remove from a drive
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16.  Tape is a magnetically coated ribbon of
plastic capable of storing large amounts of
data and information
 A tape drive reads and writes data and
information on a tape
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17.  An optical disc consists of a flat, round, portable disc
made of metal, plastic, and lacquer that is written and
read by a laser
 An optical disk is a high-capacity storage medium. An
optical drive uses reflected light to read data.
 To store data, the disk's metal surface is covered with
tiny dents (pits) and flat spots (lands), which cause
light to be reflected differently.
 When an optical drive shines light into a pit, the light
cannot be reflected back. This represents a bit value of
0 (off). A land reflects light back to its source,
representing a bit value of 1 (on).
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18.  A magnetic stripe card contains a magnetic
stripe that stores information
 A smart card stores data on a thin
microprocessor embedded in the card
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19.  A CD-Recordable (CD-R) drive lets you record
your own CDs, but data cannot be overwritten
once it is recorded to the disk.
 A CD-Rewritable (CD-RW) drive lets you
record a CD, then write new data over the
already recorded data.
 PhotoCD technology is used to store digital
photographs.
 DVD recordable
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20.  Flash memory
 Smart Cards
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