Welcome to CMPE003 Personal Computers: Hardware and Software

1. Welcome toCMPE003Personal Computers: Hardware and Software Dr. Chane Fullmer Fall 2002 UC Santa Cruz

2. Class Information • Midterm results due back Friday • HW #2 is back • Avg score = 9.93 – Excellent !! 

3. Assignments • Homework #3 – Due October 18 • Design your own Web page • Keep in mind --- • The world at large will be able to see your page • Don’t put private or sensitive information on your Web page. • Details and sample – see class page – http://www.soe.ucsc.edu/classes/cmpe003/Fall02/ If you need help uploading your files to your CATS account, take your disk to section..

4. Storage and Multimedia: The Facts and More Chapter 6

5. Objectives • List the benefits of secondary storage • Identify and describe storage media available for personal computers • Differentiate among the principal types of secondary storage • Explain how data is organized, accessed, and processed

6. Secondary Storage Benefits • Semi-permanent • Non-volatile • Reliable • Convenient – Locate and access data quickly

7. Secondary Storage Benefits • Compressed storage • Diskette – about 500 printed pages • Optical disk – about 500 books • Economy • Savings in physical storage costs • Savings in the speed and convenience of filing and retrieving data

8. Types of Storage • Magnetic Disk Storage • Optical Disks • Magneto-optical • CD-ROM • CD-R • CD-RW • DVD-ROM • Magnetic Tape Storage

9. Magnetic Disk Storage • Data represented as magnetic spots • Magnetized spot = 1 • Absence of a magnetized spot = 0 • Read • Converts the magnetized data to electrical impulses • Write • Converts electrical impulses to magnetized spots on disk

10. Size MB older hard disks GB current PC TB coming soon What’s stored? User documents Software Graphic images Audio files Video files Disk Capacity

11. Diskettes • Low capacity – small files • Portable • Flexible Mylar coated with metallic substance • Hard plastic jacket for protection • 3 ½ inch, 1.44 MB

12. High-Capacity Portable Disks • Larger files • Portable • High-capacity • 120 / 200 MB • Can read and write standard diskettes • Ex: Superdisk • Zip disk (Iomega Corp) • 250 MB • not compatible with 3 ½ inch diskettes • Also Jaz disk (2GB)

13. Data Compression • Why use? • Squeeze big files onto small disks • Speed up data transfer of files • Goal – Remove redundancy (minimize size) • Reduce to the minimal number of bits to store data • Techniques • Remove all extra space characters • Substitutes a smaller data string for a frequently occurring set of characters • Software uses formula to determine how to compress • Different models used based on content (text, image, etc) • Must be decompressed to be used again

14. Hard Disk • Various sizes • Portability • Generally non-portable • Removable hard disks available for PC • Rigid platter coated with metallic substance

15. Disk Pack Several platters Airtight, sealed module Mount disk pack on disk drive

16. Disk Pack • Disk pack has set of access arms • Two read / write heads per arm • One reads top surface • One reads bottom surface • Access arms move together as a unit • Only one read/write head works at a time

17. Data DestroyedHead Crash

18. Logical Layout of a DiskTrack • Concentric circles • Passes under read/write head as disk rotates • 1.44 MB diskette has 80 tracks on each surface • Numbered 0  79 • Each track stores the same amount of data

19. Logical Layout of a DiskSector • Pie-shaped division of track • Holds a fixed number of bytes (512 bytes) • Cluster • Adjacent sectors treated as a unit of storage • Fixed number (2-8 sectors) • Minimum space allocated to a file

20. Logical Layout of a DiskCylinder • Same track on each platter • Store files across multiple platters • Reduces access time

21. Logical Layout of a DiskZone Recording • Assigns more sectors to tracks in outer zones • More sectors = more data storage available

22. Disk DriveRead / Write Operation • Disks rotate • Access arm moves read/write head • Read / write operation begins and continues until complete • Data is transferred to/from memory

23. Access Time Components • Seek time • Travel time for moving heads over track • Head switching • Turning on correct head • Rotational delay • Waiting for sector to arrive under head (Avg ½ revolution) • Data transfer rate • Read/write bits on disk platter • Depends on density and rotational speed

24. Disk Caching • Required data read from disk into memory • Adjacent data read into disk cache (special area of memory) • Program encounters a read instruction • Checks disk cache • If present, no physical read is required • If not present, read from disk

25. RAID Redundant Array of Independent Disks

26. Optical Disk • Greater capacity than other portable media • Process • Laser writes on metallic material spread over the surface of disk • Heat from laser produces pits on disk surface • Reading – laser picks up light reflections from the pits • Technology • ROM • WORM

27. MOMagneto-optical • Hybrid • High-volume capacity • Written multiple times • Process • Laser melts a microscopic spot • Magnet aligns crystals • Reading – laser picks up light reflection from crystals

28. CD-ROMCompact Disk Read-Only Memory • High capacity portable • Read multiple times • Cannot record • Capacity – up to 680+ MB • (450 standard 3 ½ inch diskettes) • Used for software distribution

29. CD-RCompact Disc-Recordable • Cheap! – < 5 cents – or even free  • Labels are the expensive part now • High capacity • Portable • Write once • Read multiple times • CD-R drive • CD-ROM drive

30. CR-RWCompact Disk-Rewritable • High capacity • Portable • Read multiple times • Record multiple times • Some compatibility problems reading CD-RW disks on CD-ROM drives

31. DVD-ROMDigital Versatile Disk • Originally named Digital Video Disk • Larger capacity than CD-ROM • Standard – Up to 4.7 GB • 7 times more than CD-ROM • Double layers – 8.5 GB • Double-sided – 17 GB • Data is packed more densely • Read multiple times, Cannot record • Can read CD-ROM disks

32. DVD-ROMDigital Versatile Disk • Benefits • Full-length movies • Audio quality comparable to audio compact disks • High-volume business data • Expected to replace CD-ROM in the near future

33. ApplicationsMultimedia • Hardware • CD-ROM or DVD-ROM • Sound card or sound chip • Speakers • MPEG (Motion Picture Experts Group) • Video standards that support full-motion video • Faster drive provides faster data transfer and produces a smoother video

34. Magnetic Tape Storage • Plastic tape with magnetic coating • Capacity based on density – bpi or cpi • Magnetic tape unit • Read/write head • Erase head erases previously recorded data • Inferior to disks • Not as reliable • Sequential access to data • Inexpensive • Primarily for backup

35. Backup Systems • Prevent data loss • Fire • Natural disaster • Electromechanical failures of disk • User introduced errors • Software errors • Accidental data deletion • Store data in more than one place • Important data must be kept “offsite”

36. Bit Rot How long is my data good? • Not forever…… • Bit rot occurs in all media • Bit rot is a degradation of the medium itself over time • Worst  Best.. • Floppy 0 - 2 yrs • Tape 2 – 20 (with ECC) • Hard Disk 5 yrs • CD-RW 5 - 20 ? • CD-R 5 - 20 ? • DVD ???

37. Questions ?? Questions ??

38. Enjoy Your Day