Lec8chap7f04

Lecture 9 / Chapter 7 COSC1300/ITSC 1401/BCIS 1405 10/19/2004
F.Farahmand 1 / 11 File: lec8chap7f04.doc
General Items:
? H
Reading Materials:
? T
Miscellaneous:

Electronic Storage
-The medium on which we can keep data, instructions, and
information
-Examples: Floppy Disk, Tape, PC Card, etc.
-Is monitor a storage device?
-Storage Types: Primary, Secondary
Memory Devices
-Temporarily hold the data
-Used during processing
-Two basic types: V? and N?
-Also called primary storage
Storage
-Known as the secondary storage, permanent storage, mass storage
-It is nonvolatile
-May have different media – physical materials to store the data
-Examples: Floppy drive, Hard drive, Tape, etc.
-Basic operations: Search, Read, Write
-Basic properties:
o Access time: Time to locate the item (data)
?Order of msec
o Capacity: How much data can be stored
?In order of GB
o Technology and medium: Type of physical material used
?Floppy, Tape

What is the big idea?
-
Storage Devices
Primary Storage Secondary Storage
Volatile Nonvolatile FD CD
Tape DVD
HD
MEMORY
PROCESSOR
STORAGE
WORK SPACE
YOU
CABINET

Comparing Different Storage Media and Memory:
-Speed (Access time) – Memory is faster
-Capacity – Storage devices have more capacity
-Cost – Memory is more expensive
-Degradation:
Information lasts forever or five years-whichever comes first!
Difference between DISC and DISK?
- Disks (diskette) are any storage media which utilize electromagnetic
platters to store data.
o Floppy disks, Hard disks
- Discs are storage media which use the patterns of light bouncing off a
pitted surface to store data
o Compact discs, DVD discs
So is it flying DISC or DISK?
Memory
(RAM)
Compact Disc
Floppy Disk
Tape
Hard Disk

Floppy Disks
-Uses magnetic storage medium – been around since invention of
PCs
-Density
o Number of bits it can store
o Low (720 KB), High Density (1.47 MB)
Is it 1.44 or 1.47 MB Floppy?
-Evolution:
o 8-inch disk (1967)
o 5.25 Floppy – 360 KB capacity, 1981
o 3.5 Disks – 1.47MB capacity
-Basic terminologies: Uses magnetic media (plastic disks)
-Compatibility: Upward and downward compatible
o No upward compatible (can’t recognize the higher density)
-Floppy Disk Drive (FDD) parts
o Shutter, Header, Motor
o Basic operations: Search, Read, Write
-Storing capability:
o There are 40 tracks per side of the recording surface
o 18 sector per track
o 512 bytes per sector
o High density floppies have 2 sides
2 x 80 x 2 x 512 x 18 = 1,474,560 MB
o 2-8 sectors make a Cluster
o A file resides on one or more clusters

-Some related terminologies
o Formatting: process of preparing the disk for R/W
o Write-protection: Can’t write into the disk
o Back-up: File duplication
o Life time (5-7 years)
Hard Disks
-Hard disk drives
-Faster access time than floppies and have much higher capacity
-Store data magnetically
-Basic components:
o Platter: Coated glass, aluminum, or ceramic with materials
that allows recording data
o Motor: Turns the platters (72000 rpm)
o R/W Header: Mechanical moving head across the platter –
moving at 170 mph!
o Controller (HDC): Interfaces the computer and the HD –
three basic types:
-USB: Allowing daisy chain
-EIDE: Commonly used, can support up to 4 drivers at a
speed of 66 MBps, variations include ATA, DMA, etc.
-SCSI: Used for many other drivers including CD-ROM
drivers, printers – supports daisy chaining, operates at
160 MBps – other variations include SCSI-3, Ultra
SCSI, etc.

Related terminologies:
o Partitioning: Virtually splitting the HD
o Head Crash: the gap between the platter and the header is
blocked due to shocks or contamination
-2 millionths of an inch! How large is that? – Hair-proof!
o Disk Cache: Memory holding frequent data in use
o Defragmenting: removing unused space on the HD
o Internet Hard Driver: Data storage on remote servers
-Integrated hard disks: called RAID – Redundant Array of
Independent Disks
o Used for backup and reliable storage
o Can be based on 1:1 backup (mirroring)
o The data can be split into multiple disks resulting in more
reliable and space efficient storage (striping)

Compact Disc (CD)
-Also called optical disc (watch the spelling!)
-Metal disc with a bout a 5-inch diameter and 1/12th
of an inch
thickness
-Stores data, etc. using microscopic notches (called pits)
o When the light hits the pit it returns indicating a logic 1
-Types:
-Basic Operation:
o Consists of a spiral single track circling around the CD
o The track is divided into evenly sized sectors
o Pits and Bumps generate logic 1 and 0
So how small is a pit?
o The height of the bump is 125 nanometer - A nanometer is a
billionth of a meter

o Storage capacity (sound and data) :
o Let’s assume the CD can record 80 minutes of music, how many
bytes can it store?
o 44,100 samples/channel/second x 2 bytes/sample x 2 channels x 80
minutes x 60 seconds/minute = 846,720,000 bytes about 1GB
-Types:
o CD-ROM
-Read-only memory, the contents can not be changes
-Uses CD-ROM drive or player
-650MB to 1GB storage capacity (450 x more than a FD)
-Data transfer rate: 150KBps per X – 48X = 7.2 MBps
o CD-R
-Multi session recordable CD – not erasable
-Writes at about 8X and reads at about 24X rate
o CD-RW
-Rewriteable CD – Like a floppy
-Writes at about 8X / Rewrites at about 10 X / Reads at
about 24X rate
Tape
-Magnetically coated ribbon which can store data
-Uses tape cartridge
-Uses Sequential access not Direct access
o Sequential access searches for data sequentially
o Direct access (Random access)
-Accesses the data immediately
-Remember RAM?

Digital versatile disc (DVD)
o Very high capacity disc (4.7 – 17 GB)
o Better quality than CDs
o Pits are packed closer together
o Double layers of pits
o Double sided
o Types: DVD+RW, DVD-ROM, DVD-R
o How long is the track? 7.5 miles on each side!!!

Mobile Storage Devices
-Moveable thin credit card-size storage devices
-Come in different types depending on the thickness
Smart Cards
-Moveable thin credit card-size storage devices
-Basic types:
o Intelligent, and memory cards
o Examples: Calling Card? License Card? E-money?
o Are they secure?

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