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C OMPUTING

C OMPUTING. E SSENTIALS. 1999. 2000. 1999. 2000. Timothy J. O’Leary Linda I. O’Leary. 1999. Presentations by: Fred Bounds. 2000. Secondary Storage. 5. CHAPTER. Competencies. After reading this chapter, you should be able to:

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C OMPUTING

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  1. COMPUTING ESSENTIALS 1999 2000 1999 2000 Timothy J. O’Leary Linda I. O’Leary 1999 Presentations by:Fred Bounds 2000

  2. Secondary Storage 5 CHAPTER

  3. Competencies After reading this chapter, you should be able to: 1. Describe today’s standard floppy disk and compare it to Zip, SuperDisks and HiFD disks. 2. Describe the following kinds of disks: internal hard disks, hard-disk cartridges and hard-disk packs. Computing Essentials 1999 - 2000 Chapter Five

  4. Competencies 3. Describe ways to improve hard-disk operations: disk caching, redundant arrays of inexpensive disks and data compression. 4. Compare the CD and DVD optical disk formats. Computing Essentials 1999 - 2000 Chapter Five

  5. Competencies 5. Describe the different types of optical disks. 6. Describe magnetic tape streamers and magnetic tape reels. Computing Essentials 1999 - 2000 Chapter Five

  6. Overview • Computers permanently save information • For future use • To share information with others • To modify information already available • Stores programs and data • As opposed to temporary storage (RAM), which is volatile, secondary storage is nonvolatile Computing Essentials 1999 - 2000 Chapter Five

  7. Floppy Disks Floppy disks are removable storage media. Today’s standard is 1.44 MB. Tomorrow’s might be a Zip, SuperDisk or HiFD. Data is recorded on tracks and sectors.

  8. Floppy Disks • Removable storage media inserted into disk drives • Flat circular pieces of mylar plastic rotating within a jacket • The bits of data are represented by the presence or absence of magnetic charges Computing Essentials 1999 - 2000 Chapter Five

  9. Floppy Disks - Today’s Standard • Storage capacities range from 360 KB to 1.44 MB • Jackets covering the mylar disk can be flexible or sturdy • Write-protect notch or window to prevent inadvertent erasure or write-over Computing Essentials 1999 - 2000 Chapter Five

  10. Floppy Disks - Tomorrow’s Standard • Zip Disks • 100 MB capacity (70 times regular floppy) • Becoming standard feature on new systems • May be the next floppy disk standard • SuperDisks • 120 MB capacity • Can read and write standard floppies, while Zips cannot Computing Essentials 1999 - 2000 Chapter Five

  11. Floppy Disks - Tomorrow’s Standard • HiFD disks • 200 MB capacity (140 times standard floppy) • Can also read and write standard floppies Computing Essentials 1999 - 2000 Chapter Five

  12. The Parts of a Floppy Disk • Data recorded in rings called called tracks • Tracks divided into wedge-shaped sections called sectors • Most disks manufactured without tracks and sectors and must have “soft sectors” added through the formatting process Computing Essentials 1999 - 2000 Chapter Five

  13. Typical Floppy Disk Capacities 2HD 1.44 MB SuperDisk 120 MB Computing Essentials 1999 - 2000 Chapter Five

  14. access arm read-write head tracks (invisible) 3 1/2-inch floppy disk How a Disk Drive Works • Drive motor turns mylar disk • Access arm moves read-write heads back and forth • Read-write heads then read or write on the disk surface Computing Essentials 1999 - 2000 Chapter Five

  15. Hard Disks Hard disks are of three types: internal hard disk, hard-disk cartridge and hard-disk pack.

  16. Hard Disks • Composed of metallic rather than plastic disks • Fast information storage and retrieval • Read-write heads “fly” over the disk surface on a cushion of extremely thin air Computing Essentials 1999 - 2000 Chapter Five

  17. Hard Disks • A smoke particle, human hair or fingerprint could cause a head crash • Head crashes occur when the read-write head contacts the disk surface Computing Essentials 1999 - 2000 Chapter Five

  18. Materials that can cause a head crash Computing Essentials 1999 - 2000 Chapter Five

  19. Materials that can cause a head crash dust particle fingerprint smoke particle human hair Computing Essentials 1999 - 2000 Chapter Five

  20. Internal Hard Disk • Located inside the system unit • Also known as fixed disk • For storing the operating system, other programs and large data files Computing Essentials 1999 - 2000 Chapter Five

  21. Internal Hard Disk • One or more metallic platters sealed inside a container • Container holds • Motor for rotating the disks • Access arm and read-write heads Computing Essentials 1999 - 2000 Chapter Five

  22. Internal Hard Disk • Advantages over floppy disks • Capacity (up to thousands times a single floppy • Speed (ten times the speed) Computing Essentials 1999 - 2000 Chapter Five

  23. Hard-Disk Cartridges • Hard disk can be easily removed • Give microcomputer fast access to large amounts of data Computing Essentials 1999 - 2000 Chapter Five

  24. Hard-Disk Cartridges • Complements internal hard disk • Typical capacity, 2 GB • Popular vendors: Iomega and SyQuest Computing Essentials 1999 - 2000 Chapter Five

  25. Hard-Disk Packs • Removable, massive storage capacity • Common in mainframe systems • Composed of a larger number of platters, resembling a stack of record albums Computing Essentials 1999 - 2000 Chapter Five

  26. Hard-Disk Packs • Most platters offer read-write surfaces on top and bottom • Used with larger computer systems Computing Essentials 1999 - 2000 Chapter Five

  27. Hard-Disk Packs • Access time - time between the computer’s request for data from secondary storage and the completion of the data transfer Computing Essentials 1999 - 2000 Chapter Five

  28. Performance Enhancements • Disk caching • Uses hardware and software to anticipate data needs • Frequently used data is stored in memory, when needed, the access time is much faster Computing Essentials 1999 - 2000 Chapter Five

  29. Performance Enhancements • Redundant arrays of inexpensive disks (RAID) • Groups of low cost hard-disk drives grouped together using networks and special software • Performs as a single large-capacity disk • But faster than a single disk of comparable size Computing Essentials 1999 - 2000 Chapter Five

  30. Performance Enhancements • File compression and decompression • Increase storage capacity • Reduce space required for storage • Aids in file transmission • WinZip and PKZip are well-known programs Computing Essentials 1999 - 2000 Chapter Five

  31. Optical Disks Optical disks use laser technology. CD and DVD are optical disk formats.

  32. Optical Disks • Compact, high capacity form of permanent storage • Laser beam writes by creating a pattern of pits (holes) and lands (flat areas) to encode data bits • Laser beams reflect off the pits and lands to read the data Computing Essentials 1999 - 2000 Chapter Five

  33. Optical Disks • Up to 4.7 gigabytes of data • Equivalent of over 1 million typewritten pages • Three types of optical discs CD-ROM, CD-R and erasable optical discs, or CD-RW Computing Essentials 1999 - 2000 Chapter Five

  34. CD-ROM • Stands for compact disc-read-only memory • Can be read from, but not written to • Can hold up to 650 MB of information • Grolier Electronic Encyclopedia - nine million words and 1900 pictures • Used to distribute large software packages Computing Essentials 1999 - 2000 Chapter Five

  35. Reflected light Reflecting surface Laser beam CD-ROM drive CD-ROM How a CD-ROM works CD-ROM carrying case Computing Essentials 1999 - 2000 Chapter Five

  36. CD-R • Stands for CD-Recordable • Also known as WORM, or write once, read many • Ideal for use as permanent data archives for essential company information • CD changers or CD jukeboxes can facilitate rapid access to large amounts of information Computing Essentials 1999 - 2000 Chapter Five

  37. CD-RW • Also known as rewritable optical discs • Unlike CD-R, these discs can be written on numerous times • Most common technology is magneto-optical (MO) disc drive, combining magnetic and optical technologies • Capacities up to 1,000 megabytes (a gigabyte) Computing Essentials 1999 - 2000 Chapter Five

  38. Digital Versatile Disk • Commonly known as digital video disk or DVD • Up to 4.7 gigabytes capacity, seven times CD • With two-sided storage, 17 gigabytes out soon • Predicted to replace CD as a standard Computing Essentials 1999 - 2000 Chapter Five

  39. Digital Versatile Disk • DVD-ROM - provide high quality, movie length videos • DVD-R - consumer recordable version just getting started • DVD-RAM or DVD-RW - rewritable version Computing Essentials 1999 - 2000 Chapter Five

  40. Magnetic Tape Magnetic tape streamers and magnetic tape reels are used primarily for backup purposes.

  41. Magnetic Tape • Disks offer fast, direct access to data programs • Tapes are sequential access, because they have to be fast forwarded or rewound before a specific location can be reached Computing Essentials 1999 - 2000 Chapter Five

  42. Magnetic Tape • A common sequential access method of permanent storage method • A common form of data backup in companies with larger computer systems Computing Essentials 1999 - 2000 Chapter Five

  43. Magnetic Tape • Two forms of tape storage • Magnetic tape streamers • Magnetic tape reels Computing Essentials 1999 - 2000 Chapter Five

  44. Backup tape cartridge units used with microcomputer systems Typical capacities range from 120 MB to 5 GB Advanced forms use digital audio tape (DAT) Magnetic Tape Streamers Computing Essentials 1999 - 2000 Chapter Five

  45. Magnetic Tape Reels • Used with minicomputer and mainframe computers • Often 1/2 inch wide and 1/2 mile long • Stores 1600 to 6400 characters per inch • Tapes are run on magnetic tape drives or magnetic tape units Computing Essentials 1999 - 2000 Chapter Five

  46. Magnetic Tape Reels • Used with minicomputer and mainframe computers • Often 1/2 inch wide and 1/2 mile long • Stores 1600 to 6400 characters per inch • Tapes are run on magnetic tape drives or magnetic tape units Computing Essentials 1999 - 2000 Chapter Five

  47. Read-write head Erase head Magnetic Tape Reels Take-up reel Supply reel Tape Computing Essentials 1999 - 2000 Chapter Five

  48. Computing Essentials 1999 - 2000 Chapter Five

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