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									      Computers:
Information Technology
     in Perspective

                Larry Long & Nancy Long




Computers: Information Technology in Perspective
               By Long and Long
       Copyright 2002 Prentice Hall, Inc.
       Copyright 2002 Prentice Hall, Inc.
Storing & Retrieving
     Information

                                              Chapter 4




    Computers: Information Technology in Perspective
                   By Long and Long
           Copyright 2002 Prentice Hall, Inc.
                    See What’s New
 4.3         Quit




Monthly
Technology
Update
              Mass Storage and Files
4.4    Quit




       Programs and information (text,
        image, audio, video) are stored:
           Temporarily in RAM
           Permanently in Mass Storage (disk
            and tape)
                    Computer Files
 Quit



 ASCII  file
                               .exe
 Data file
 Document file          .wav .mdb
 Spreadsheet file          .txt .xls
 Web page file                        .htm
 Source program file                    .vdp
 Executable program file
                                  .gif
                                      .bmp
 Graphics file           .jpg
                                  .tif
 Audio file
 Video file                  .mov
        File Name Conventions
 Quit




                            separated by a period



2001 Resume.doc

          filename               file extension
        (up to 255 chars)   (1 - 3 characters, optional)
             What do we do with files?
4.7         Quit




       Create, name, save
       Copy, move, delete
       Retrieve, update
       Display, play, print
       Execute                 Download,  upload
                                Export, import
                                Compress (zip/unzip)
                                Protect
      Physical Storage Process
      Quit




Storage medium


                           Storage device



         Storage process
      –Sequential and/or Random
      –Write/Save
      –Read/Open
                                Magnetic Disks
               Quit




           Interchangeable Disks
              Offline and Online


            Hard/Fixed Disks
                  Online only

Magnetic
Disk
                  The Diskette
Quit




        3.5”Floppy: 1.44 MB
        SuperDisk: 120 MB
        HiFD disk: 200 MB
        Zip Disk: 100 or 250 MB



                Disk density
                         Diskette Care
4.12    Quit




        Do store in protected spot, away from
         sun and magnets
        Do remove before turning off computer
        Do clean them periodically
        Don’t expose to extreme temperatures
        Don’t touch surface
        Don’t remove if drive light is on
        Don’t force it in/out of the drive
                                            Hard Disks
 4.13                     Quit




                Fasterand more storage than diskettes
                10 GB to >75 GB permanently installed
                1-2 GB interchangeable Jaz®
                Anatomy:
                       Recording surface
                       Multiple platters

                       Read/write head

                       Access arms

Courtesy of Seagate
Technology
              Fixed Hard Disk
4.14   Quit
       Head Crash
Quit
       Magnetic Disk Organization
4.17     Quit



        VFAT:  Virtual File    Disk   Speed
         Allocation Table           Access time
        ScanDisk   for lost        Data transfer rate
         clusters
                                    Disk caching
        Defragmentation

        Formatting
                    Computer Viruses
4.18    Quit




        Via Internet when downloading files
        Via e-mail as attachments
        Via diskette
        Via computer networks
        Use anti-viral program for your hard
         disks and UPDATE IT often!
                           Backing Up Files
4.19         Quit




        Magnetic   Tape used for:
          Backup or protection
          Archiving

        Tape backup units (TBUs)
        Data cartridge
        Inexpensive and can store > 1 GB
                        Backing Up Files
4.20    Quit




        Backup     methods:
            Full
            Selective

            Modified files only

        Other   backup options:
            Server computer
            Notebook/desktop PC

            CD-R or CD-RW

            Interchangeable external hard disk
                Backing Up Files
4.21   Quit




               Internet   and network
               servers
                 Must be made fault-
                  tolerant
                 Use RAID (Redundant
                  Array of Independent
                  Disks) for backup
                 Optical Laser Devices
          Quit




                      Spiraling Track

                                             Less sensitive
                                 Detector   to environment


                                    Pit
                                            Cheaper than
                                            magnetic disks

                                  Land
                                              Large data
                                               capacity
Optical                          Sector
Storage
  Optical Disks: Write-Only
Quit




        CD-ROM
         Compact Disk: read only memory
         Cannot be altered
         Speeds: 32X, 40X or 75X (spin rate)
         Jukeboxes
         Capacity: 650 MB

        DVD-ROM
         Capacity: 4.7 GB to 17 GB
         Backward compatible with CD-ROM
  Optical Disks: Read/Write
  Quit




 CD-R                      DVD-R
     Compact disk-         DVD-RAM
      recordable                Rewritable
 CD-RW
                            FMD-ROM
     Compact disk-             Capacity up to 140 GB
      rewritable                 and backward
     Will not work with         compatible
      older CD-ROM
      drives
                         Cost Comparison
4.25         Quit




                             RAM - $1/Mb

       Hard disk < $.1/Mb

                    CD - fraction of $.01/Mb
Storing & Retrieving
     Information

                                                The End




    Computers: Information Technology in Perspective
                   By Long and Long
           Copyright 2002 Prentice Hall, Inc.

								
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