DVD ROM DVD разработка

DIGITAL VERSATILE DISC-READ ONLY MEMORY (DVD-ROM)

Digital versatile disc-read only memory (DVD-ROM) is a read-only digital versatile disc (DVD) commonly used for storing large software applications. It is similar to a compact disk-read only memory (CD-ROM) but has a larger capacity. A DVD-ROM stores around 4.38 GB of data. A CD-ROM usually stores 650 MB of data. A personal computer (PC) with a DVD-ROM or a DVD-RAM drive is designed to read a DVD-ROM disc. A DVD-ROM permanently stores data files which cannot be changed, written over or erased. Generally a DVD-ROM disc is not equipped to be used with a DVD drive connected to a home theater system or television. But many DVD-ROM drives can generally read a DVD movie disc.

A DVD-ROM is one of the various types of DVDs. A blank DVD is generally a DVD-R or DVD+R, which has a read-write format. The +R or -R references the format standards and is a rewritable or recordable DVD.

Compared to a CD-ROM, a DVD-ROM has the same 5 inch diameter and 1.2 millimeter (mm) thickness. But because a DVD-ROM uses a shorter wavelength laser with tighter compacted pits, the disc capacity is increased. In fact, the smallest DVD-ROM can store approximately 7 times more data than a CD-ROM.

This term is also known as digital video disc ROM.

The DVD-ROM was first introduced in 1996 by the DVD Forum, a group of ten international companies using and developing DVD and HD DVD formats for media, software and hardware. The DVD Forum consists of the founding companies plus over 220 other members. The DVD Forum also releases all DVD specifications published in the DVD books by titles such as DVD-ROM Book or DVD-R Book.Japan produced the first DVD-ROMs in November 1996. By March 1997 it was introduced in the United States.

A typical DVD-ROM can hold up to 17 GB/s of data if both sides of the disc are writable.

The DVD-ROM is comprised of two 0.6 millimeters (mm) acrylic layers bonded together. The double-sided disc consists of two recordable grooved sides. With two layers, a DVD’s laser beam only has to go through 0.06 mm to reach the recording layer. The spiral path begins at the center of the disc and coils numerous times until it reaches the outer edge. With a double-layered disc the path continues to the second layer. Having a thin layer allows the lens to focus the beam to a smaller spot size, which in turn writes smaller pits for more data. The data is encoded in the form of spiral pits that are merely nanometers apart. A double-sided disc needs to be manually turned over and the path resumes in the center.

Prerecorded DVDs are mass-produced using molding machines that physically stamp data onto the DVD. Such discs are a form of DVD-ROM because data can only be read and not written or erased. Blank recordable DVD discs (DVD-R and DVD+R) can be recorded once using a DVD recorder and then function as a DVD-ROM. Rewritable DVDs (DVD-RW, DVD+RW, and DVD-RAM) can be recorded and erased many times.

DVDs are used in DVD-Video consumer digital video format and in DVD-Audio consumer digital audio format as well as for authoring DVD discs written in a special AVCHD format to hold high definition material (often in conjunction with AVCHD format camcorders). DVDs containing other types of information may be referred to as DVD data discs.

The Oxford English Dictionary comments that, "In 1995 rival manufacturers of the product initially named digital video disc agreed that, in order to emphasize the flexibility of the format for multimedia applications, the preferred abbreviation DVD would be understood to denote digital versatile disc." Toshiba had been using the name ‘digital video disc’, but that was switched to ‘digital versatile disc’ after computer companies complained that it left out their applications."The OED also states that in 1995, "The companies said the official name of the format will simply be DVD. "Digital versatile disc" is the explanation provided in a DVD Forum Primer from 2000 and in the DVD Forum's mission statement.

A CD/DVD-ROM computer drive

In computing, an optical disc drive (ODD) is a disc drive that uses laser light or electromagnetic waves within or near the visible light spectrum as part of the process of reading or writing data to or from optical discs. Some drives can only read from certain discs, but recent drives can both read and record, also called burners or writers. Compact discs, DVDs, and Blu-ray discs are common types of optical media which can be read and recorded by such drives. Optical disc drives that are no longer in production include CD-ROM drive, CD writer drive, combo (CD-RW/DVD-ROM) drive, and DVD writer drive supporting certain recordable and rewritable DVD formats (such as DVD-R(W) only, DVD+R(W) only, DVD-RAM only, and all DVD formats except DVD-R DL). As of 2015, DVD writer drive supporting all existing recordable and rewritable DVD formats is the most common for desktop PCs and laptops. There are also the DVD-ROM drive, BD-ROM drive, Blu-ray Disc combo (BD-ROM/DVD±RW/CD-RW) drive, and Blu-ray Disc writer drive.

Optical disc drives are an integral part of standalone appliances such as CD players, DVD players, Blu-ray disc players, DVD recorders, certain desktop video game consoles, such as Sony PlayStation 4, Microsoft Xbox One, Nintendo Wii U, and Sony PlayStation 3, and certain portable video game consoles, such as Sony PlayStation Portable. Floppy disk drives, with capacity of 1.44 MB, have been made obsolete: optical media are cheap and have vastly higher capacity to handle the large files used since the days of floppy discs, and the vast majority of computers and much consumer entertainment hardware have optical writers. They are also very commonly used in computers to read software and consumer media distributed on disc, and to record discs for archival and data exchange purposes. USB flash drives, high-capacity, small, and inexpensive, are suitable where read/write capability is required.

Disc recording is restricted to storing files playable on consumer appliances (films, music, etc.), relatively small volumes of data (e.g. a standard DVD holds 4.7 gigabytes) for local use, and data for distribution, but only on a small scale; mass-producing large numbers of identical discs is cheaper and faster than individual recording.

Optical discs are used to back up relatively small volumes of data, but backing up of entire hard drives, which as of 2015 typically contain many hundreds of gigabytes or even multiple terabytes, is less practical. Large backups are often instead made on external hard drives, as their price has dropped to a level making this viable; in professional environments magnetic tape drives are also used.