Hard disc drives

Hard disc drives are discussed here

USB keys (memory sticks)

These use Flash Ram.

Storage capacity = between 256Kb and 1Gb (as of 6/1/2005)

Floppy discs

3.5 inch DS/DD (double sided, double density)

Storage capacity = approx 800Kb

3.5 unch HD (high density)

Storage capacity = 1.4Mb

Optical - CD (Compact Disc)

Storage capacity = between 650 and 740Mb

This can be extended up to 800Mb through a process known as "over-burning", though there is no guarantee that all CD drives will be able to access the extra data.

NOTE: Some of the different compact disc standards are discussed in our article on CD mastering

CD-ROM

Storage capacity = 650Mb (+ 90Mb error correction data)

If a blank disc is used to backup computer files in data, or CD-ROM format, approximately 90Mb of capacity is used for error correction purposes, leaving 650Mb for data.

Red book audio CDs

Storage capacity = 740Mb (74 minutes)

If a computer CD-R blank disc is used to create a so called "Red book" audio disc, suitable for domestic audio players, all 740Mb of capacity can be used for music. Error correction is handled by the players themselves.

If the files are burnt in data, or CD-ROM format (as .wav, .aiff, or .mpg etc) capacity is as CD-ROM (650Mb).

NOTE: Computers CD-R drives can create red book audio CDs from computer CD-R blank discs (avoid CD-RW for this purpose). Domestic audio CD recorders use pre-formatted CD-Audio discs.