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