{{unreferenced, date=April 2019 Squareholepunch

computer science Computer science is the study of computation, automation, and information. Computer science spans theoretical disciplines (such as algorithms, theory of computation, information theory, and automation) to practical disciplines (includi ...

, a double-sided disk is a disk of which both sides are used to store data. Early floppy disks only used one surface for recording. The term ''single-sided disk'' was not common until the introduction of the double-sided disk, which offered double the capacity in the same physical size. Initially, double-sided disks had to be removed and flipped over to access data on the other side, but eventually devices were made that could read both sides without the need to eject the disk. Manufacturers sold both single-sided and double-sided disks with the double-sided disks being typically 50% more expensive than single-sided disks. While the magnetic-coated medium was coated on both sides, the single-sided floppies had a read-write notch on only one side, thus allowing only one side of the disk to be used. When users discovered this, they began buying the less-expensive single-sided disks and "notching" them using scissors, a hole punch, or a specially-designed "notcher" to allow them to write to the reverse side of the disk.

DVD The DVD (common abbreviation for Digital Video Disc or Digital Versatile Disc) is a digital optical disc data storage format. It was invented and developed in 1995 and first released on November 1, 1996, in Japan. The medium can store any kind ...

s also are available in single-sided and double-sided formats, often as an alternative to two-disc packages. Both sides can be either single layered (DVD-10) or dual layered (DVD-18) or both (DVD-14). When used for movie releases, double-sided DVDs typically have the

widescreen Widescreen images are displayed within a set of aspect ratios (relationship of image width to height) used in film, television and computer screens. In film, a widescreen film is any film image with a width-to-height aspect ratio greater than t ...

(or

letterboxed Letterboxing is the practice of transferring film shot in a widescreen aspect ratio to standard-width video formats while preserving the film's original aspect ratio. The resulting videographic image has mattes (black bars) above and below ...

) version of the movie on one side, and the

pan and scan Pan and scan is a method of adjusting widescreen film images so that they can be shown in fullscreen proportions of a standard-definition 4:3 aspect ratio television screen, often cropping off the sides of the original widescreen image to focus ...

(sometimes called "fullscreen") version on the other side. Other releases place the feature on Side A, and the extra features on the Side B. Longer films would be divided between the two sides, starting on Side A and continuing on Side B, and include a prompt for when to flip the disc (identically to a LaserDisc). It is more convenient (and cheaper) for movies to be released on single-sided discs, with the film and extras on the same side, and widescreen and letterbox versions packaged separately. Indeed, a few DVD titles that were initially issued as double-sided discs were later reissued as two single-sided disc sets.

DualDisc The DualDisc is a type of double-sided optical disc product developed by a group of record companies including Michael Jackson, MJJ Productions Inc., EMI, EMI Music, Universal Music Group, Sony BMG, Sony BMG Music Entertainment, Warner Music Group, ...

and

DVDplus The DVDplus is a dual-sided disc similar to the DualDisc. It is an optical disc storage technology that combines the technology of DVD and CD in one disc. A DVD and a CD-compatible layer are bonded together to provide a multi-format hybrid disc. ...

are two variants on the double-sided DVD format where one side is a

compact disc The compact disc (CD) is a digital optical disc data storage format that was co-developed by Philips and Sony to store and play digital audio recordings. In August 1982, the first compact disc was manufactured. It was then released in Oc ...

. Both formats were created as potential successors to the compact disc format; in particular, the ability to include both audio and video features on the DVD side was intended to boost album sales by providing consumers with an added incentive to purchase physical albums instead of downloading pirated MP3s. However, both disc formats failed to make any long-lasting commercial impact and faded into obscurity by the end of the 2000s, due to competition from digital downloads and the

Super Audio CD Super Audio CD (SACD) is an optical disc format for audio storage introduced in 1999. It was developed jointly by Sony and Philips Electronics and intended to be the successor to the Compact Disc (CD) format. The SACD format allows multiple a ...

and

DVD-Audio DVD-Audio (commonly abbreviated as DVD-A) is a digital format for delivering high-fidelity audio content on a DVD. DVD-Audio uses most of the storage on the disc for high-quality audio and is not intended to be a video delivery format. The st ...

formats and because of physical design flaws that impeded DualDiscs and DVDplus discs' compatibility with many commercial CD players. Specifically, the CD side of a DualDisc was much thinner than a standard CD (whereas the DVD side was thick enough to meet standardized specifications), offsetting it from the focal length of CD players' infrared lasers, while DVDplus discs were much thicker than both standard CDs and standard DVDs, causing the discs to have difficulties fitting into slot-loading players and disc changers.

See also