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Chapter 7 Storage

Chapter 7 Storage. Storage. Next. What is storage ?. Holds data, instructions, and information for future use. Storage medium is physical material used for storage. Also called secondary storage. p. 7.02 Fig. 7-1. Storage. Kilobyte (KB). 1 thousand. Megabyte (MB). 1 million.

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Chapter 7 Storage

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  1. Chapter 7Storage

  2. Storage Next • What isstorage? • Holds data, instructions, and information for future use • Storage mediumis physical material used for storage • Also called secondary storage p. 7.02 Fig. 7-1

  3. Storage Kilobyte (KB) 1 thousand Megabyte (MB) 1 million Gigabyte (GB) 1 billion Terabyte (TB) 1 trillion Next • What iscapacity? • Number of bytes (characters) a storage medium can hold p. 7.04

  4. Storage Memory(most RAM)(chips on motherboard) Screen Display Storage Medium(floppy disks, Zip disks,hard disks, CDs) Next • How does volatility compare? • Storage medium is nonvolatile—contents retained when power is off • Memory is volatile—holds data and instructions temporarily ON OFF Display appears Display disappears Volatile Data andinstructions available to user Data and instructions erased Contents available to user Contents retained Nonvolatile p. 7.04

  5. Storage Functions as source of input Creates output Next • What is astorage device? Hardware that records and retrieves items to and from storage media Reading Process of transferring items from storage media to memory Writing Process of transferring items from memory to storage media p. 7.04

  6. Storage Next • What isaccess time? • Time it takes storage device to locate item on storage medium • Time required to deliver item from memory to processor p. 7.04

  7. Floppy Disks Next • What is afloppy disk? shutter • Portable, inexpensive storage medium (also called diskette) shell liner magneticcoating Thin, circular, flexible film enclosedin 3.5” wide plastic shell metal hub flexible thin film p. 7.05 Fig. 7-5

  8. Floppy Disks Next • What is afloppy disk drive? • Device that reads from andwrites to floppy disk Floppy disk drive built intoa desktop computer • One floppy drive, named drive A • If two floppy drives, second designated as drive B • Also called secondary storage External floppy disk drive attaches toa computer with a cable p. 7.06 Fig. 7-6

  9. Floppy Disks Trackis narrow recording bandthat forms fullcircle on disk Sectorstores up to512 bytesof data Next • What aretracks andsectors? Formatting prepares disk for use and marks bad sectors as unusable p. 7.07 Fig. 7-8

  10. Floppy Disks Capacity: 144 MB Sides: 2 Tracks: 80 Sectors per track: 512 Sectors per disk: 2880 Next • How do you compute a disk’s storage capacity? • Multiply number of sides, number of tracks, number of sectors per track, and number of bytes per sector • For high-density disk: 2 sides  80 tracks  18 sectors per track  512 bytes per sector = 1,474,560 bytes Characteristics of a3.5-inch High-DensityFloppy Disk p. 7.08

  11. Floppy Disks Next • How do you care for a floppy? • Proper care helps maximize disk’s life • Floppy disk can last at least seven years Never open theshutter andtouch the disk’ssurface Avoid exposureto heat andcold Avoid exposureto magneticfields Avoid exposureto contaminantssuch as dust,smoke, orsalt air Keep disks ina storage traywhen notusing them p. 7.08

  12. Floppy Disks write-protected notch openmeans youcannot writeon the disk not write-protected hole on thisside meansdisk is highdensity notch closedmeans youcan write onthe disk Next • What is awrite-protect notch? • Small opening with a cover that you slide • Protects floppy disk from being erased accidentally p. 7.08 Fig. 7-10

  13. Zip® Disks Zip disk ExternalZip drive Next • What is aZip disk? • Magnetic medium that stores 100 MB or 250 MB of data • Used to back up and to transfer files • Zip disks require aZip drivec—chigh capacity drive that reads from and writes on a Zip disk c p. 7.09 Fig. 7-11

  14. Hard Disks Next hard disk installedin system unit • What is ahard disk? • High-capacity storage • Consists of several inflexible, circular platters that store items electronically • Components enclosed in airtight, sealed case for protection p. 7.09 Fig. 7-12

  15. Hard Disks Sample Hard Disk Characteristics Advertised capacity 40 GB Platters 2 Read/write heads 4 Cylinders 16,383 Bytes per second 512 Sectors per track 63 Sectors per drive 78,165,360 Revolutions per minute 7,200 Transfer rate 100 MB per second Access time 9 ms Next • What are characteristics of a hard disk? actualdiskcapacity p. 7.10 Fig. 7-13

  16. Hard Disks Next • What is ahead crash? • Occurs when read/write head touches platter surface • Spinning creates cushion of air that floats read/write head above platter • Clearance between head and platter is approximately two-millionths of an inch • A smoke particle, dust particle, or human hair could render drive unusable hair read/write head dust clearance smoke platter p. 7.12 Fig. 7-16

  17. Hard Disks processor disk cache first requestfor data—to disk cache second requestfor data—to hard disk hard disk Next • What is adisk cache? • Portion of memory that processor uses to store frequently accessed items p. 7.12 Fig. 7-17

  18. Hard Disks Next • What areexternal hard disksandremovable hard disks? • Used to back up or transfer files External hard disk—freestandinghard disk that connects to system unit Removable hard disk—hard diskthat you insert and removefrom hard disk drive p. 7.13 Fig. 7-18

  19. Hard Disks Next • What is anInternet hard drive? • Service on Web that provides storage for minimal monthly fee • Files can be accessed from any computer with Web access • Large files can be downloaded instantaneously • Others can be authorized to access your data p. 7.14 Fig. 7-19

  20. CDs and DVDs Next • What areCDs and DVDs? Push the button toslide out the tray. • Flat, round, portable metal discs with protective plastic coating • Can be read only or read/write Insert the disc,label side up. • Most PCs include CD or DVD drive, most play audio CDs Push the same buttonto close the tray. p. 7.15 Fig. 7-20

  21. CDs and DVDs disc label lens lens pit land Step 3.Reflected light is deflected to alight-sensing diode, which sends digital signals of 1 to computer. Absence of reflected light is read as digital signal of 0. 0 1 prism prism light-sensingdiode light-sensingdiode laserdiode laserdiode Next • How does a laser read data on a CD or DVD? Step 2.If light strikesa pit, it scatters. If light strikes a land, it is reflected back toward diode. Step 1.Laser diode shines a light beam towarddisc. p. 7.16 Fig. 7-21

  22. CDs and DVDs Next • How is data stored on a CD or DVD? • Typically stored in singletrack • Track divided into evenly sizedsectorsthat store items single trackspirals to edgeof disc disc sectors p. 7.16 Fig. 7-22

  23. CDs and DVDs Click to view Web Link, then click CD-ROMsbelow Chapter 7 Next • What is aCD-ROM? • Compactdiscread-onlymemory • Cannot erase or modify contents • Typically holds 650 MB to 1 GB • Commonly usedto distributemultimedia and complexsoftware p. 7.17 Fig. 7-24

  24. CDs and DVDs Next • What is the data transfer rate of a CD-ROM drive? Ranges from 48X to 75X or faster 75X 75  150 KBps = 11,250 KBps or 12.25 MBps 75X is 150 KBps (KB per second) 48X: 48  150 KBps = 7,200 KBps or 7.2 MBps p. 7.18

  25. CDs and DVDs Next • What areCD-Rs and CD-RWs? Must haveCD recorderor CD-R drive CD-R (compact disc-readable) —cdisc you can write on once Cannot erasedisc’s contents CD-RW (compact disc-rewritable) —ceerasable disc you can write onmultiple times Must haveCD-RW softwareand CD-RW drive p. 7.20

  26. CDs and DVDs Next • What is aDVD-ROM? • High capacity disc capable of storing 4.7 GB to 17 GB • Must haveDVD-ROM driveor DVD player to read DVD-ROM • Stores databases, music, complex software, and movies DVD DVD drive p. 7.22 Fig. 7-27

  27. CDs and DVDs DVD-ROM Storage Capacities Sides Layers Storage Capacity 1 1 47 GB 1 1 8.5 GB 2 1 9.4 GB 2 2 17 GB Next • How does a DVD-ROM store data? • Two layers of pits are used, lower layer is semitransparent so laser can read through • Some are double-sided • DVD+RWis a rewritable DVD p. 7.22 Fig. 7-28

  28. Tape Next • What istape? • Magnetically coated plastic ribboncapable of storing large amountsof data at low cost • Primarily used for backup p. 7.24 Fig. 7-29

  29. Tape Next • How is data stored on a tape? • Sequential access • Reads and writes data consecutively, like music tape • Unlike direct access— used on floppy disks, Zip disks, hard disks, CDs, and DVDs — which can locate particular item immediately p. 7. 24 Fig. 7-30

  30. PC Cards Next • What is aPC Card? • Adds capabilities to computer • Credit-card-sized device commonlyused in notebook computers p. 7.24 Figs. 7-31–7-32

  31. Miniature Mobile Storage Media Next • What isminiature mobile storage media? • Storage for small mobile devices Miniaturemobile storagemedia p. 7.25 Fig. 7-33

  32. Miniature Mobile Storage Media CompactFlash Smart Media Secure Digital ™ USBDrive ® Memory Stick Next • What are common types of miniature mobile storage media? p. 7.26

  33. Miniature Mobile Storage Media Next • What is acard reader? • Reads information stored on miniature mobile storage media • Type of card determines type of card reader needed http://h30015.www3.hp.com/hp_dpc/tour_directPrint/GS_direct_print_FL.asp# p. 7.27 Fig. 7-35

  34. Miniature Mobile Storage Media Next • What is asmart card? • Stores data on microprocessor embedded in small card • Input, process, output, and storage capabilities • Sometimes calledintelligentsmart card smart card p. 7.27 Fig. 7-36

  35. Microfilm and Microfiche Microfilm — 100- to215-foot roll of film Microfiche — small sheet of film, usually 4”  6” Next • What aremicrofilmandmicrofiche? Store microscopic images of documents on roll or sheet of film Images recorded using computer output microfilm recorder p. 7.28 Fig. 7-37

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