Copyright Prentice Hall, Inc. 1 Computers: Information Technology in Perspective, 11e Larry Long and Nancy Long Chapter 5 Storing and Retrieving Information

Copyright Prentice Hall, Inc.2 Objectives Once you have read and studied this chapter, you will have learned:  The relationship between mass storage and the various types of files.  The various types of magnetic disk devices and media, including organization, principles of operation, maintenance, performance considerations, and security concerns.  The operational capabilities and applications for the various types of optical laser disc storage.  The sources of computer viruses and approaches to protecting your system from these viruses.  Methods and procedures for backing up disk files.

Copyright Prentice Hall, Inc.3 Why this chapter is important to you! Understanding the types of storage media available will help you to make productive purchasing decisions Learning about the different types of storage media could help to get you organized

Copyright Prentice Hall, Inc.4 Mass Storage Programs and information are stored in both RAM and permanent mass storage Programs and information are retrieved from storage and held in RAM Types:  Magnetic disk drives  Magnetic tape drives

Copyright Prentice Hall, Inc.5 Files A file is a recording of information File types are determined by the program (Word.doc) Files need organization We create files, save, files, copy files, download files, compress files, and lots more…

Copyright Prentice Hall, Inc.6 File Management Files are usually stored in folders or subfolders in Windows Files can be saved, opened, copied, cut, deleted, and/or renamed

Copyright Prentice Hall, Inc.7 Magnetic Disks Magnetic disks have random- or direct- access capabilities  Example: choose song three on a CD They are fast at seeking and retrieving information

Copyright Prentice Hall, Inc.8 Hardware and Storage Media Two types of magnetic disks:  Interchange Stored offline Loaded when needed  Fixed magnetic disk Permanently installed Accessible

Copyright Prentice Hall, Inc.9 The Diskette Interchangeable  Must be protected  Types Diskette  3.5 floppy  Holds 1.44 MB SuperDisk or HiFD  Holds 120 MB to 200 MB Zip  Holds 100 MB  Newer: 750 MB

Copyright Prentice Hall, Inc.10 The Hard Disk Fixed magnetic disk Hard disk  1 to 5.25 inches  20 GB to 200 GB  Contains 12 disk platters stacked on a spindle  Disk spins over a read/write head  Access arms float over the disk Portable hard disk  External hard disk Interchangeable hard disk  Portable hard disk to swap out

Copyright Prentice Hall, Inc.11 Magnetic Disk Organization Data are stored in tracks  80 tracks on a diskette  Thousands on hard disks Sectors are used to store and retrieve data  Recording surface is divided in pie slices  Hard disks have thousands of sectors Adjacent sectors form clusters  Each cluster is numbered

Copyright Prentice Hall, Inc.12 The File Allocation Table Cluster information is stored in the VFAT What happens  OS searches the VFAT for the first cluster  Read/write heads move over the track  Information is read and transmitted  OS looks for other clusters  OS directs to read the additional clusters

Copyright Prentice Hall, Inc.13 Defragmenting Disk Defragmenter  Consolidates files into contiguous clusters  Minimizes read/write head movement  The read/write heads is the most vulnerable part of the PC system

Copyright Prentice Hall, Inc.14 Formatting Before using a disk it must be formatted  Formatting creates sectors and tracks to store data  Formatting sets up the VFAT

Copyright Prentice Hall, Inc.15 Disk Speed Data access is performed in electronic speeds Moving the read/write heads and spinning the disk can slow speed Data transfer rate is the rate at which data are read from storage to RAM or written to storage from RAM Disk caching improves speed

Copyright Prentice Hall, Inc.16 Optical Laser Discs May replace magnetic and tape storage Two lasers replace the read/write head  One writes to the surface  The other reads data from the light-sensitive surface Spiraling Track Detector Pit Land Sector

Copyright Prentice Hall, Inc.17 CD-ROM and DVD-ROM CD-ROM  Spin off of audio CDs  Read-only memory  Data cannot be altered  Data is stored in the form of pits and lands DVD-ROM  Pits and lands are packed more densely Both are cheaper to make and hold a lot of information

Copyright Prentice Hall, Inc.18 Rewritable Optical Laser Disc Options CD-R  Recordable CD-RW  Allows users to rewrite just like on a Magnetic disk DVD-RW  Rewrite capabilities  Little more costly  DVD can read both DVD and CD-ROM formats FMD-ROM on the way  Holds up to 140 GM

Copyright Prentice Hall, Inc.19 What is the Best Mix of Storage Options? More storage  More costs More RAM  More costs More speed  More costs

Copyright Prentice Hall, Inc.20 Viruses and Virus Protection A virus program  Infects programs, documents, databases and more  It is man-made  It can hide and reproduce  It can lay dormant and then activate  Anti-virus programs can help

Copyright Prentice Hall, Inc.21 Types of Computer Viruses Macro viruses  Written into the program macro  Shuts down functions Worm  A program that makes copies of itself  It will interfere with normal operations

Copyright Prentice Hall, Inc.22 Sources of Computer Viruses Three primary sources  The Internet Via downloads and exchanges  Diskettes Exchanging disks  Computer networks Can spread from one network to another

Copyright Prentice Hall, Inc.23 Virus Protection Antivirus program  Must install and keep updated  What it will do: Delete s that are suspicious Alert you before opening a file Scans downloaded files

Copyright Prentice Hall, Inc.24 Backing up Files Safeguard your contents  Choose a backup plan Full Selective Incremental  Choose your media Rewritable Diskettes High-capacity Portable hard disk Server Another PC And more…

Copyright Prentice Hall, Inc.25 Summary Mass Storage Files File Management Magnetic Disks Optical Laser Discs Viruses and Virus Protection Backing Up Files