Bit rot

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Bit Rot, or Bit Decay is a colloquial computing term used either to describe gradual decay of storage media or to facetiously describe the spontaneous degradation of a software program over time. The latter use of the term implies that software can literally wear out or rust like a physical tool. more commonly, bit rot refers to the decay of physical storage mediums.

1 Decay of storage media
2 Problems with software
3 Other uses of the term
4 See also
5 References
6 External link

[edit] 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 very real phenomenon of data stored in EPROMs gradually decaying over the duration of many years, or in the decay of data stored on CD or DVD disks or other types of consumer storage.

The cause of bit rot varies depending on the medium. Floppy disk and magnetic tape storage may experience bit rot as bits lose magnetic orientation. In 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 punch cards may experience a more literal form of bit rot, as the paper onto which the programs are stored begins to rot.

Bit rot is also used to describe the discredited idea ^[1] that a computer's memory may occasionally be altered by cosmic rays.

[edit] Problems with software

Main article: Software rot

The term "bit rot" is often used to refer to dormant code rot, i.e. the fact that dormant (unused or little-used) code gradually decays in correctness as a result of interface changes in active code that is called from the dormant code.

When a program that has been running correctly for an extended time suddenly malfunctions for no apparent reason, programmers often jokingly attribute the failure to bit rot. Such an effect may be due to a memory leak or other nonobvious software bug. Many times, although there is no obvious change in the program's operating environment, a subtle difference has occurred that is triggering a latent software error.

[edit] Other uses of the term

Rarely, bit rot is referred to as the process by which data becomes inaccessible due to the lack of working devices to read old data storage formats. (For example, a game stored on a floppy disk may be referred to as having succumbed to bit rot if the user no longer possesses a floppy disk drive to read the disk).

Another use of the term "Bit Rot" is the slowing of performance of a PC over time from continued use. This is mostly apparent with Microsoft Windows PCs where the accumulation of old data (or "cruft") on a hard drive seems to impede the performance of that OS. One cause of this is installing and later uninstalling software that leaves traces (library files, fonts, etc) behind; spyware, viruses, and trojan horses are other causes.