Write once read many

Write once read many (times) or WORM is a classification of computer storage media. It is used to describe media that can only be written once. After they are written, they can only be read.

There are two different kinds of such media:

• In some, the hardware prevents multiple writes, examples of such media are the CD-R and DVD-R discs. There is also some kind of computer memory (called PROM) which can only be written once.
• Certain kind of media use a software solution to emulate this behaviour. Examples are certain kinds of backup tapes and harddisks that can also have this property.

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