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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