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Chapter 7 Storage

Chapter 7 Storage. Chapter 7 Objectives. Storage media and storage devices Magnetic disks Floppy disks Zip disks Hard disks Optical discs CD-ROM, CD-R, CD-RW DVD-ROM Tape. Storage. Next. What is storage ?. Holds data, instructions, and information for future use.

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Chapter 7 Storage

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  1. Chapter 7Storage

  2. Chapter 7 Objectives • Storage media and storage devices • Magnetic disks • Floppy disks • Zip disks • Hard disks • Optical discs • CD-ROM, CD-R, CD-RW • DVD-ROM • Tape

  3. Storage Next • What isstorage? • Holds data, instructions, and information for future use • Storage mediumis physical material used for storage • Also called secondary storage p. 354 Fig. 7-1

  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. 356

  5. Storage Kilobyte (KB) 1 thousand Megabyte (MB) 1 million Gigabyte (GB) 1 billion Terabyte (TB) 1 trillion Petabyte (PB) 1 quadrillion Exabyte (EB) 1 quintillion Zettabyte (ZB) 1 sextillion Yottabyte (YB) 1 septillion Next • What iscapacity? • Number of bytes (characters) a storage medium can hold p. 356

  6. 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. 356

  7. Storage Stores … Primary Storage Memory (most RAM) Items waiting to be interpretedand executed by the processor Secondary Storage Hard Disk Operating system, applicationsoftware, user data and information Flash Memory Cards and USB Flash Drives Digital pictures or files to be transported CDs and DVDs Software, backups, movies, music Tape Backups Floppy Disk Small files to be transported Next • What isaccess time? • Time it takes storage device to locate item on storage medium • Time required to deliver item from memory to processor fastertransferrates slowertransferrates p. 357 Fig. 7-4

  8. Magnetic 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 Cluster is the smallest unit of disk space that stores data and information. p. 357 Fig. 7-5

  9. Magnetic Disks Click to view Web Link, click Chapter 7, Click Web Link from left navigation, then click Floppy Disks below Chapter 7 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. 358

  10. Magnetic 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 • Also called secondary storage External floppy disk drive attaches toa computer with a cable p. 358 Fig. 7-6

  11. Magnetic Disks Capacity: 1.44 MB Sides: 2 Tracks: 80 Sectors per track: 18 Bytes per sector: 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. 359

  12. Magnetic 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. 359 Fig. 7-7

  13. Magnetic Disks Click to view Web Link, click Chapter 7, Click Web Link from left navigation, then click Zip Disks below Chapter 7 Next • What is aZip disk? • Magnetic medium that stores 100 MB to 750 MB of data • Used to back up and to transfer files • Backup is duplicate of file, program, or disk in case original is lost • Zip disks require aZip drivec—chigh capacity drive that reads from and writes on a Zip disk c p. 359 Fig. 7-9

  14. Magnetic 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. 360 Fig. 7-10

  15. Magnetic Disks Sample Hard Disk Characteristics Advertised capacity 120 GB Platters 3 Read/write heads 6 Cylinders 16,383 Bytes per second 512 Sectors per track 63 Sectors per drive 234,441,648 Revolutions per minute 7,200 Transfer rate 133 MB per second Access time 8.9 ms Next • What are characteristics of a hard disk? actualdiskcapacity p. 361 Fig. 7-11

  16. Magnetic Disks Next platter • What is acylinder? track • Vertical section of track through all platters sector • Single movement of read/write head arms accesses all plattersin cylinder read/writehead platter sides p. 362 Fig. 7-13 cylinder

  17. Magnetic 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. 362 Fig. 7-14

  18. Magnetic 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. 363 Fig. 7-15

  19. Optical Discs Next • What areoptical discs? Push the button toslide out the tray. • Flat, round, portable discs made of metal, plastic, and lacquer • Can be read only or read/write Insert the disc,label side up. • Most PCs include an optical disc drive Push the same buttonto close the tray. p. 366 Fig. 7-19

  20. Optical Discs 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 an optical disc? 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. 367 Fig. 7-20

  21. Optical Discs Next • How is data stored on an optical disc? • Typically stored in singletrack • Track divided into evenly sizedsectorsthat store items single trackspirals to edgeof disc disc sectors p. 367 Fig. 7-21

  22. Optical Discs Click to view Web Link, click Chapter 7, Click Web Link from left navigation, 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 used to distribute multimedia and complex software p. 369 Fig. 7-24

  23. Optical Discs 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 1X is 150 KBps (KB per second) 48X: 48  150 KBps = 7,200 KBps or 7.2 MBps p. 369

  24. Optical Discs Click to view Web Link, click Chapter 7, Click Web Link from left navigation, then click CD-Rs and CD-RWs below Chapter 7 Next • What areCD-Rs and CD-RWs? Must haveCD recorderor CD-R drive CD-R (compact disc-recordable) —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 softwareandCD-RW drive p. 371

  25. Optical Discs Click to view Web Link, click Chapter 7, Click Web Link from left navigation, then click DVDs below Chapter 7 Next • What is aDVD-ROM(digital versatile disc-ROM or digital video disc-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 p. 372 Fig. 7-26

  26. Optical Discs 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 • Blue-Ray discs currently have a storage capacity of up to 27 GB p. 372 Fig. 7-27

  27. Tape Click to view Web Link, click Chapter 7, Click Web Link from left navigation, then click Tape below Chapter 7 Next • What istape? • Magnetically coated plastic ribboncapable of storing large amountsof data at low cost • Primarily used for backup p. 374 Fig. 7-28

  28. 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. 374

  29. Miniature Mobile Storage Media Click to view Web Link, click Chapter 7, Click Web Link from left navigation, then click Smart Cards below Chapter 7 Next • What is asmart card? • Stores data on microprocessor embedded in small card • Input, process, output, and storage capabilities p. 378 Fig. 7-35

  30. 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. 379 Fig. 7-36

  31. Microfilm and Microfiche Next • How do life expectancies of various media compare? • Microfilm and microfiche have longest life of any storage media p. 379 Fig. 7-37

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