Write protection is any physical mechanism that prevents writing, modifying, or erasing

data In the pursuit of knowledge, data (; ) is a collection of discrete values that convey information, describing quantity, quality, fact, statistics, other basic units of meaning, or simply sequences of symbols that may be further interpret ...

on a device. Most commercial software, audio and video on writeable media is write-protected when distributed.

Examples

* IBM -inch

magnetic tape Magnetic tape is a medium for magnetic storage made of a thin, magnetizable coating on a long, narrow strip of plastic film. It was developed in Germany in 1928, based on the earlier magnetic wire recording from Denmark. Devices that use magnet ...

reels, introduced in the 1950s, had a circular groove on one side of the reel, into which a soft plastic ring had to be placed in order to write on the tape. ("No ring, no write.") *

Audio cassette The Compact Cassette or Musicassette (MC), also commonly called the tape cassette, cassette tape, audio cassette, or simply tape or cassette, is an analog magnetic tape recording format for audio recording and playback. Invented by Lou Otte ...

s and VHS

videocassette Videotape is magnetic tape used for storing video and usually sound in addition. Information stored can be in the form of either an analog or digital signal. Videotape is used in both video tape recorders (VTRs) and, more commonly, videocasset ...

s have tabs on the top/rear edge that can be broken off (uncovered = protected). * 8 and -inch floppies can have, respectively, write-protect and write-enable notches on the right side (8-inch punched = protected; -inch covered/notch not present = protected). A common practice with single-sided floppies was to punch a second notch on the opposite side of the disk to enable use of both sides of the media, creating a flippy disk, so called because one originally had to flip the disk over to use the other side. * -inch

floppy disk A floppy disk or floppy diskette (casually referred to as a floppy, or a diskette) is an obsolescent type of disk storage composed of a thin and flexible disk of a magnetic storage medium in a square or nearly square plastic enclosure lined ...

s have a sliding tab in a window on the right side (open = protected). * Iomega Zip disks were write-protected using the IomegaWare software. *

Syquest SyQuest Technology, Inc. () was an early entrant into the hard disk drive market for personal computers. The company was founded on January 27, 1982 by Syed Iftikar who had been a founder of Seagate, along with Ben Alaimo, Bill Krajewski, Anil N ...

EZ-drive (135 & 250 MB) disks were write-protected using a small metal switch on the rear of the disk at the bottom. *

VHS-C VHS-C is the compact VHS videocassette format, introduced by Victor Company of Japan (JVC) in 1982, and used primarily for consumer-grade compact analog recording camcorders. The format is based on the same video tape as is used in VHS, and ...

Video8 The 8mm video format refers informally to three related videocassette formats. These are the original Video8 (analog recording) format and its improved successor Hi8 (analog video and analog audio but with provision for digital audio), as well as ...

, Hi8, and DV

s have a sliding tab on the rear edge. * Iomega ditto tape cartridges had a small sliding tab on the top left hand corner on the front face of the cartridge. *

USB flash drive Universal Serial Bus (USB) is an industry standard that establishes specifications for cables, connectors and protocols for connection, communication and power supply ( interfacing) between computers, peripherals and other computers. A bro ...

s sometimes have a small switch, though this has become uncommon. An example of a USB flash drive that supported write protection via a switch is the Transcend JetFlash series. *

Secure Digital Secure Digital, officially abbreviated as SD, is a proprietary non-volatile flash memory card format developed by the SD Association (SDA) for use in portable devices. The standard was introduced in August 1999 by joint efforts between SanDis ...

(SD) cards have a write-protect tab on the left side. * Extensively, media that, by means of design, can't operate outside from this mode:

CD-R CD-R (Compact disc-recordable) is a digital optical disc storage format. A CD-R disc is a compact disc that can be written once and read arbitrarily many times. CD-R discs (CD-Rs) are readable by most CD readers manufactured prior to the i ...

DVD-R DVD recordable and DVD rewritable are optical disc recording technologies. Both terms describe DVD optical discs that can be written to by a DVD recorder, whereas only 'rewritable' discs are able to erase and rewrite data. Data is written ('bu ...

Vinyl records A phonograph record (also known as a gramophone record, especially in British English), or simply a record, is an analog sound storage medium in the form of a flat disc with an inscribed, modulated spiral groove. The groove usually starts near ...

, etc. These mechanisms are intended to prevent only accidental data loss or attacks by

computer virus A computer virus is a type of computer program that, when executed, replicates itself by modifying other computer programs and inserting its own code. If this replication succeeds, the affected areas are then said to be "infected" with a comput ...

es. A determined user can easily circumvent them either by covering a notch with adhesive tape or by creating one with a

punch Punch commonly refers to: * Punch (combat), a strike made using the hand closed into a fist * Punch (drink), a wide assortment of drinks, non-alcoholic or alcoholic, generally containing fruit or fruit juice Punch may also refer to: Places * Pu ...

as appropriate, or sometimes by physically altering the media transport to ignore the write-protect mechanism. Write-protection is typically enforced by the hardware. In the case of computer devices, attempting to violate it will return an error to the

operating system An operating system (OS) is system software that manages computer hardware, software resources, and provides common daemon (computing), services for computer programs. Time-sharing operating systems scheduler (computing), schedule tasks for ef ...

while some tape recorders physically lock the record button when a write-protected cassette is present.

Write blocking

Write blocking, a subset of write protection, is a technique used in

computer forensics Computer forensics (also known as computer forensic science) is a branch of digital forensic science pertaining to evidence found in computers and digital storage media. The goal of computer forensics is to examine digital media in a forensica ...

in order to maintain the integrity of data storage devices. By preventing all write operations to the device, e.g. a

hard drive A hard disk drive (HDD), hard disk, hard drive, or fixed disk is an electro-mechanical data storage device that stores and retrieves digital data using magnetic storage with one or more rigid rapidly rotating platters coated with mag ...

, it can be ensured that the device remains unaltered by data recovery methods. Hardware write blocking was invented by Mark Menz and Steve Bress (US patent 6,813,682 and EU patent EP1,342,145). Both hardware and software write-blocking methods are used; however, software blocking is generally not as reliable, due to human error.

References

{{Reflist *http://www.patentstorm.us/patents/6813682.html (US patent 6,813,682)

Examples

Write blocking

References

See also