Decay of Storage Media
Bit rot is often defined as the event in which the small electric charge of a bit in memory disperses, possibly altering program code.
Bit rot can also be used to describe the phenomenon of data stored in EPROMs and flash memory gradually decaying over the duration of many years, or in the decay of data stored on CD or DVD discs or other types of consumer storage.
The cause of bit rot varies depending on the medium. EPROMs and flash memory store data using electrical charges, which can slowly leak away due to imperfect insulation. The chip itself is not affected by this, so re-programming it once per decade or so will prevent the bit rot. The biggest problem can be finding a clean copy of the chip to make the copy from; frequently by the time the user discovers the bit rot there are no un-damaged chips to use as a master.
Floppy disk and magnetic tape storage may experience bit rot as bits lose magnetic orientation, and in warm, humid conditions these media are prone to literal rotting. In optical discs such as CDs and DVDs the breakdown of the material onto which the data is stored may cause bit rot. This can be mitigated by storing disks in a dark, cool location with low humidity. Archival quality disks are also available. Old punched cards and punched tape may also experience literal rotting. Mylar punched tape is available for use in this situation.
Bit rot is also used to describe the idea that semiconductor RAM may occasionally be altered by cosmic rays, a phenomenon known as soft error.
Read more about this topic: Bit Rot
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