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National Child Exploitation Coordination Centre (NCECC) - Fact Sheets - Data Storage

Data Storage

File system : A system that an operating system uses to organize and keep track of its files.

FAT: (File Allocation Table)

  • Used by the operating system to locate files on a disk.
  • Files may be divided into many sections that are scattered around the disk. The FAT keeps track of all the pieces.
  • FAT formatted partitions cannot be larger than 32gb

NTFS: (NT File System)

  • This file system is a journaling file system, which means it is less likely to become corrupt and will recognize bad sectors and correct itself.
  • To control access to files, you can set permissions for directories and/or files. NTFS can only be used by Windows NT, 2000, and XP.
  • The NTFS contains an MFT (Master File Table) that keeps track of files on disks.

Types of Memory

  • RAM(random-access memory): Data is able to be written and read to and from this RAM. Most RAM is volatile, which means that it requires a steady flow of electricity to maintain its contents. As soon as the power is turned off, whatever data was in RAM is lost.
  • ROM (read-only memory): This holds instructions for starting up the computers. Rom cannot be written to. ROMs are non-volatile.
  • PROM (programmable read-only memory): A PROM is a memory chip on which you can store a program. After the PROM has been used, you cannot wipe it clean and use it to store something else. PROMs are non-volatile.
  • EPROM (erasable programmable read-only memory): An EPROM is a special type of PROM that can be erased by exposing it to ultraviolet light.
  • EEPROM(electrically erasable programmable read-only memory): An EEPROM is a special type of PROM that can be erased by exposing it to an electrical charge.

Storage Sizes

Bit : The smallest unit of information on a machine. A single bit can hold only one of two values: 0 or 1. Eight consecutive bits are equal to one byte.

Byte : A unit of storage capable of holding a single character.

Kilobyte – 1,024 bytes
Megabyte - 1,048,576 bytes
Gigabyte – 1,073,741,824 bytes
Terabyte – 1,099,511,627,776 bytes

Storage Devices

Floppy Disks: A soft magnetic disk to store data

  • Relatively slow
  • Small capacity
  • Portable
  • Inexpensive
  • Universal

Hard Drive : A hard magnetic disk to store data

  • Very fast
  • More capacity than floppy disks
  • Expensive
  • Not portable

Tapes: A magnetically coated strip of plastic on which data can be encoded

  • Relatively inexpensive
  • Portable
  • Large storage capacities
  • Do not permit random access of data

CD-ROM: A Storage medium which can be read and which is written by lasers

CD-R – CD-Writable

  • Can only be written to once
  • Inexpensive
  • Cannot be erased
  • Portable
  • Multi-session recording allows the user to add layers of data at a later date
  • Requires a CD burner

CD-RW – CD-Rewritable

  • Can be written to multiple times
  • Slightly more expensive than a CD-R
  • Can be erased
  • Portable
  • Requires a CD burner

DVD-ROM: A new type of storage medium that is written by lasers and can be read

DVD-R

  • Write-once disks
  • Excellent compatibility with both standalone DVD players and DVD-ROM drives
  • Requires a DVD-R burner to write to disk

DVD-RW

  • Rewriteable discs
  • Majority of standalone DVD players will play video recorded on DVD-RW discs
  • Requires a DVD-R burner to write to disk

DVD+R

  • Not supported by the DVD Forum
  • Write-once disks
  • Excellent compatibility with both standalone DVD players and DVD-ROM drives
  • Requires a DVD+/-R burner to write to disk

DVD+RW

  • Not supported by the DVD Forum
  • Rewriteable discs
  • Majority of standalone DVD players will play video recorded on DVD+RW discs
  • Requires a DVD+/-R burner to write to disk

DVD+/-R Single sided dual layered

  • Holds up to 9.4gb of storage
  • Majority of standalone DVD players will play video recorded on DVD-RW discs
  • Requires a dual layered DVD+/-R burner

USB Drive : A small portable hard drive that plugs into the USB port on a computer

  • Easy-to-use
  • Small enough to be carried in a pocket
  • Plug into any computer with a USB drive
  • Durable because they do not contain any internal moving parts
  • Less storage capacity than an external hard drive

Flash Memory Cards: A type of EEPROM that can be erased and written in blocks

  • Small
  • High data storage capacity
  • Not interchangeable with other flash memory
  • Used in such items as Cellular Phones, Personal digital assistants, Digital cameras and Digital printers

References

www.webopedia.com

What is a memory Card?

http://www.bhphotovideo.com/bnh/controller/
home?O=getpage.jsp&A=getpage&Q=Product_Resources/memcard.jsp

Produced by:
The National Child Exploitation Coordination Centre
Strategic and Operations Support Services
Research and Development Division