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CD-RW (Compact Disc-Rewritable) is a digital optical disc storage format introduced by Ricoh in 1997. [1] A CD-RW compact disc (CD-RWs) can be written, read, erased, and re-written. CD-RWs, as opposed to CDs, require specialized readers that have sensitive laser optics.
CD-R (Compact disc-recordable) is a digital optical disc storage format. A CD-R disc is a compact disc that can only be written once and read arbitrarily many times. CD-R discs (CD-Rs) are readable by most CD readers manufactured prior to the introduction of CD-R, unlike CD-RW discs.
Packet writing can be used both with once-writeable media and rewriteable media. Several competing and incompatible packet writing disk formats have been developed, including DirectCD and InCD. The standardized formats for packet writing are the Universal Disk Format in the plain, VAT, and spared builds.
Formatting a disk for use by an operating system and its applications typically involves three different processes. [e]Low-level formatting (i.e., closest to the hardware) marks the surfaces of the disks with markers indicating the start of a recording block (typically today called sector markers) and other information like block CRC to be used later, in normal operations, by the disk ...
Deleting files and directories of a CD-R using packet writing technology does not recover the space occupied by these objects but, rather, they are simply marked as being deleted (making them effectively hidden). Similarly, changes to files cause new instances to be created instead of replacing the original files.
Comparison of several forms of disk storage showing tracks (not to scale); green denotes start and red denotes end. * Some CD-R(W) and DVD-R(W)/DVD+R(W) recorders operate in ZCLV, CAA or CAV modes. The digital data on a CD begins at the center of the disc and proceeds toward the edge, which allows adaptation to the different sizes available.
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]
A compressed audio optical disc, MP3 CD, or MP3 CD-ROM or MP3 DVD is an optical disc (usually a CD-R, CD-RW, DVD-R or DVD-RW) that contains digital audio in the MP3 file format. Discs are written in the "Yellow Book" standard data format (used for CD-ROMs and DVD-ROMs), as opposed to the Red Book standard audio format (used for CD-DA audio CDs).