ICT-INFO 1- Topic 5 Selection and use of storage requirements,media and devices

Topic 5

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  • Created by: Kathryn
  • Created on: 30-10-11 15:40

Topic 5

 Selection and use of storage requirements,media and devices

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Primary and Secondary storage

Primary- In chips inside computer- ROM- Read only memory - RAM -Random access memory available immeadiatley by the CPU 

Secondary- Backup 

  • Magnetic disk
  • Magnetic Tape
  • CD-ROM (compact disk read only memory)
  • CD-RW (compact disk re-writable)
  • DVD
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  • Fast 
  • Temporary 
  • Programs
  • Data
  • Stored only when power is supplied
  • On a computer chip
  • Called Volatile Memory because the contents dissapear when no power is supplied
  • Read/write so can be altered by user

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  • Fast
  • Permenant
  • Holds instructions to start computer
  • Held on a computer chip
  • Called non-volatile memory because doesn't dissapear when power is turned off
  • Contents cannot be altered by user
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Importance of memory size

If you have a large memory then:

  •  Applications run faster on their own
  • More applications can run at once
  • Quickly move between applications
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Measuring storage capacity and performance

Storage Capacity- How much data can be held

Storage Density- How compact it is

Access Time- How long it takes to access data

Transfer Rate- How long it takes to transfer data onto the computer from the device

Physical Size- Need to be as small and light as possible

Portability- Some need to be removable 

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File Sizes

Bit (0 or 1) the smallest unit


Kilobyte (Kb)- 1000 bytes

Megabyte (Mb)- 1000 kilobytes

Gigabyte (Gb)- 1000 megabytes

Terabyte (Tb)- 1000 gigabytes

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File Compession

  • Before Saving
  • Enables more files to be saved
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Storage Device Capacities

CD- Typical storage capacity- 700Mb

Flash Drive- Typical storage capacity- 4Gb

Magnetic hard drive-Typical storage capacity- 320Gb

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Magnetic Disk Drives

Floppy disks and drives:

  • Flexible plastic disks
  • Coated with a material which can store data as a magnetic pattern
  • Removable
  • Transferable
  • Not popular 
  • Low transfer speed
  • Very low storage capacity 1.44Mb

Hard drives:

  • Series of disks
  • Magnetic coating
  • Series of read/write heads
  • High transfer rate
  • High storage capacity
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Optical Drives


  • Software
  • Read only
  • Data is stored as an optical pattern
  • Large storage capacity 600Mb

CD-R (compact disk recordable)

  • Data can be stored only once


  • Store over and over again
  • Low transfer rate
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Optical drives continued

DVD (digital versatile disk)

  • High storage
  • Multimedia files (mp3,video,images)


  • Movies
  • Read only
  • Reading of data off a CD


  • Write
  • Read data
  • 4.7Gb for old
  • 8.5Gb for newer
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Magnetic Tape

  • Plastic magnetic coated tape
  • Stored on a reel
  • Huge storage capacity (around 800Gb) 
  • Back up of data and programs in large systems
  • Takes time for the data to be found
  • Suitable for an e-commerce business 
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Flash/pen drives

  • Very popular
  • Cheap
  • Large storage capacity (up to 30Gb)
  • Ideal for photographs,music and other data files
  • Printed circuit boards enclosed in a plastic case
  • Small and lightweight
  • No moving parts
  • Reliable
  • Work when scratched 
  • Easily stolen
  • Often left in computer by mistake and lost
  • Not got a high transfer rate
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Memory card drives and memory cards

  • Thin cards
  • Ideal for photographs but can be used for other types of data too
  • Many computers and printers have drives to read them 
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Data stored at different physical locations from w

  • Networked computers
  • A Blog
  • On-line backup websites 
  • Websites
  • Emails
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Limitations of storage devices and media

Ideal storage device would be:

  • Cheap
  • Very large storage capacity
  • Extremely fast access time
  • Extremely high transfer rate
  • Robust
  • Not be affected by scratches,heat,magnetic fields etc
  • Small size
  • Attach to different devices eg digital cameras, computer etc

This doesn't exist so compromise will have to be made

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Back up storage

  • Hold copies of original files
  • Don't need to be immediately accessible by the computer
  • Pen/flash drives
  • CD-RW And DVD-RW
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