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As of 2007 DVD is the de facto standard for pre-recorded movies, and popular storage of data beyond the capacity of CD. With the development of high-definition television , and the popularization of broadband and digital storage of movies, a further format development took place, again giving rise to two camps: HD DVD and Blu-ray , based upon a ...
DVDs offer significantly higher storage capacity than compact discs (CD) while having the same dimensions. A standard single-layer DVD can store up to 4.7 GB of data, a dual-layer DVD up to 8.5 GB. Variants can store up to a maximum of 17.08 GB. [11] Prerecorded DVDs are mass-produced using molding machines that physically stamp data onto the ...
In the history of optical storage media there have been and there are different optical disc formats with different data writing/reading speeds. Original CD-ROM drives could read data at about 150 kB/s, 1× constant angular velocity (CAV), [1] the same speed of compact disc players without buffering.
DVD lens supports a different focus for CD or DVD media with same laser. With the newer Blu-ray Disc drives, the laser only has to penetrate 0.1 mm of material. Thus the optical assembly would normally have to have an even greater focus range. In practice, the Blu-ray optical system is separate from the DVD/CD system.
Optical discs can be reflective, where the light source and detector are on the same side of the disc, or transmissive, where light shines through the disc to be detected on the other side. Optical discs can store analog information (e.g. Laserdisc), digital information (e.g. DVD), or store both on the same disc (e.g. CD Video).
The CD-ROM itself may contain "weak" sectors to make copying the disc more difficult, and additional data that may be difficult or impossible to copy to a CD-R or disc image, but which the software checks for each time it is run to ensure an original disc and not an unauthorized copy is present in the computer's CD-ROM drive. [citation needed]
Paper data storage, e.g. punched cards, punched tapes (now obsolete) Examples of removable media that are standalone plug-and-play devices that carry their own reader hardwares include: USB flash drives [5] Portable storage devices. Dedicated external solid-state drives (SSD) Enclosured mass storage drives, i.e. modified hard disk drives (HDD ...
A live CD (also live DVD, live disc, or live operating system) is a complete bootable computer installation including operating system which runs directly from a CD-ROM or similar storage device into a computer's memory, rather than loading from a hard disk drive.