A computers RAM is
There are two ways in which data can be retrieved from storage media.
This applies to tapes. It means that to get data the reading device must start at the beginning of the tape and move through the tape in-order until the piece of data is found. This takes time and so serial access is normally slower than direct access.
This applies to disc media and solid state media. Direct access means that data can be retrieved from anywhere on the media without the need to move through in order.
|Floppy Disc||Fixed Hard Disc|
|Portable Hard Disc||Magnetic Tapes|
|CD ROM & DVD ROM||CD R & DVD R|
|CD-RW & DVD-RW||DVD RAM|
|Memory Sticks & Pen Drives||Flash Memory Cards|
Floppy discs used to be the most common way of saving data so that it could be moved from one computer to another. They have the following features
These are the most common type of backing storage in modern PCs. They normally hold all of the installed programs and data for the PC while it is switched off.
Internally these are identical to fixed hard discs. The differences are
These are not common in home or small business environments. They are popular in large companies with centralised computer facilities which require huge amounts of storage for backing up files. Mainframe computers will connect to many of these tapes on tape machines.
These are both read-only optical storage discs. They are both 12cm in diameter. CD-ROMs can store about 700 MB while DVD-ROMs can store up to 17 GB
These are both examples of 'Write-once Read Many' (WORM) optical storage media. They are purchased as blank media and can be written to with user data only once but then read from many times.
Compact Disk Rewritable & Digital Versatile Disc Rewritable.
A competing technology to DVD-RW.
Becoming the new format for movies and possibly replacing DVDs in the future. They use a blue laser to record more data onto a disc which is the same physical size as a DVD.
Use flash memory which is 'solid-state' meaning that it contains no moving parts (unlike disks which require drives with moving parts).
Same technology as for memory sticks but packaged as cards of varying sizes and types. Common in cameras, handheld computers and modern mobile phones.