Welcome to CMPE003 Personal Computer Concepts: Hardware and Software Winter 2003 UC Santa Cruz Instructor: Guy Cox

January 23, Assignments Assignment #6 – The Last One Due March 12, 2003 Spreadsheets – (MS Excel) Generate a monthly budget spreadsheet l

January 23, Final Project Due no later than March 19, 2003 You can turn in earlier.. Power Point presentation 4 pages Extra points for special effects, animations Turn in on a floppy/CDROM

Storage and Multimedia: The Facts and More Chapter 6

January 23, 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

January 23, Secondary Storage Benefits Semi-permanent Non-volatile Reliable Convenient – Locate and access data quickly

January 23, 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 Secondary Storage Benefits

January 23, Types of Storage Magnetic Disk Storage Optical Disks Magneto-optical CD-ROM CD-R CD-RW DVD-ROM Magnetic Tape Storage

January 23, 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

January 23, Disk Capacity Size MB older hard disks GB current PC TB coming soon Whats stored? User documents Software Graphic images Audio files Video files

January 23, Diskettes Low capacity – small files Portable Flexible Mylar coated with metallic substance Hard plastic jacket for protection 3 ½ inch, 1.44 MB

January 23, 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) and Peerless (10/20GB)

January 23, 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

January 23, Hard Disk Various sizes Portability Generally non-portable Removable hard disks available for PC Rigid platter coated with metallic substance Now available are external, portable hard disks

January 23, Disk Pack Several platters Airtight, sealed module Mount disk pack on disk drive

January 23, 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

January 23, Data Destroyed: Head Crash

January 23, Logical Layout of a Disk: Track 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

January 23, Logical Layout of a Disk: Sector 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

January 23, Same track on each platter Store files across multiple platters Reduces access time Logical Layout of a Disk: Cylinder

January 23, Logical Layout of a Disk: Zone Recording Assigns more sectors to tracks in outer zones More sectors = more data storage available

January 23, Disk Drive: Read / Write Operation Disks rotate Access arm moves read/write head Read / write operation begins and continues until complete Data is transferred to/from memory

January 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

January 23, 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

January 23, RAID Redundant Array of Independent Disks

January 23, 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

January 23, MO: Magneto-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

January 23, CD-ROM: Compact 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

January 23, CD-R: Compact 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

January 23, CR-RW: Compact Disk-Rewritable High capacity Portable Read multiple times Record multiple times Some compatibility problems reading CD-RW disks on CD-ROM drives

January 23, DVD-ROM: Digital 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

January 23, Benefits Full-length movies Audio quality comparable to audio compact disks High-volume business data Expected to replace CD-ROM in the near future DVD-ROM: Digital Versatile Disk

January 23, 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 Applications: Multimedia

January 23, 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

January 23, 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

January 23, 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.. Floppy0 - 2 yrs Tape 2 – 20 (with ECC) Hard Disk5 yrs CD-RW ? CD-R ? DVD???

January 23,