Storing & Retrieving
Information
File systems
Computers: Information Technology in Perspective
By Long and Long
Copyright 2002 Prentice Hall, Inc. J. Holvikivi 2012
Mass Storage and Files
4.2
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 Programs
and information (text,
numbers, image, audio, video) are
stored:
Temporarily in RAM
 Permanently in Mass Storage (disks,
flash memory and cloud)

Computer Files
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 ASCII
file (txt), Unicode
.exe
 Data file
.wav .mdb
 Document file: doc,
docx, odt, pdf, xps
.txt .xls
.html
 Spreadsheet file
 Source program file .js
.vdp
 Executable program file .exe .gif
.bmp
 Graphics file
.jpg
.tif
 Audio file mp3
.mov
 Video file
File Name Conventions
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separated by a period
2001 Resume.doc
filename
file extension
(up to 255 chars)
(1 - 4 characters, optional)
Physical Storage Process
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Storage medium
Storage device
Storage process
–Sequential and/or Random
–Write/Save
–Read/Open
–Encryption
Magnetic Disks
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Interchangeable Disks
Offline and Online
Hard/Fixed Disks
Online only
Magnetic
Disk
Mechanical device
Hard Disks
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4.8
 Fast
and lots of storage
 >400 GB permanently installed
 - 1 TB external
 Anatomy:
Recording surface
 Multiple platters
 Read/write head
 Access arms

Courtesy of Seagate
Technology
Fixed Hard Disk
4.9
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Magnetic Disk Organization
4.11
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 VFAT:
Virtual File
Allocation Table
 CheckDisk
for repairs
 Defragmentation
 Formatting
 Disk
Speed

Access time

Data transfer rate

Disk caching
Memory device Care
4.12
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 Do
store in protected spot, away from
sun and magnets, phones
 Do remove before turning off computer
 Mark clearly and add a string!
 Don’t expose to extreme temperatures
 Don’t touch surface (CD)
 Don’t remove if drive light is on
 Don’t force it in/out of the drive
Computer Viruses
4.13
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 Via
Internet when downloading files,
video, Flash and pdf
 Via e-mail as attachments or links
 Via USB memory
 Via computer networks and peer to
peer networks
 Also in mobile devices
 Use anti-viral and network
security program and
UPDATE it automatically!
Backing Up Files
4.14
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 Back-ups
used for:
 Backup or protection
 Archiving
 Tape backup units (TBUs)
 CD-RW,
DVD, Blu-ray
 External hard disk
 Flash memory, SSD (SSD solid
state drive)
 On networks: servers or cloud
Backing Up Files
4.15
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 Backup
methods:
Full
 Selective
 Modified files only

 Internet
and network servers
Must be made fault-tolerant
 Use RAID (Redundant Array of
Independent Disks) for backup
 NAS network access server

Speed Comparison
4.16
Quit
processor
RAM
bus
Hard disk
USB flash memory
Blu-ray, DVD, CD
Storing & Retrieving
Information
The End
Computers: Information Technology in Perspective
By Long and Long
Copyright 2002 Prentice Hall, Inc.