General Items: Reading Materials: Miscellaneous: Lecture 9 / Chapter 7 COSC1300/ITSC 1401/BCIS /19/2004 ? H ? T

Transcription

1 General Items:? H Reading Materials:? T Miscellaneous: F.Farahmand 1 / 11 File: lec8chap7f04.doc

2 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 F.Farahmand 2 / 11 File: lec8chap7f04.doc

3 What is the big idea? Storage Devices Primary Storage Secondary Storage Volatile Nonvolatile FD HD CD - Tape DVD WORK SPACE YOU CABINET MEMORY PROCESSOR STORAGE F.Farahmand 3 / 11 File: lec8chap7f04.doc

4 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! Memory (RAM) Hard Disk Compact Disc Floppy Disk Tape 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? F.Farahmand 4 / 11 File: lec8chap7f04.doc

5 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 F.Farahmand 5 / 11 File: lec8chap7f04.doc

6 - 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. F.Farahmand 6 / 11 File: lec8chap7f04.doc

7 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) F.Farahmand 7 / 11 File: lec8chap7f04.doc

8 Compact Disc (CD) - Also called optical disc (watch the spelling!) - Metal disc with a bout a 5-inch diameter and 1/12 th 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 F.Farahmand 8 / 11 File: lec8chap7f04.doc

9 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? F.Farahmand 9 / 11 File: lec8chap7f04.doc

10 Digital versatile disc (DVD) o Very high capacity disc ( 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!!! F.Farahmand 10 / 11 File: lec8chap7f04.doc

11 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? F.Farahmand 11 / 11 File: lec8chap7f04.doc