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A compact-disk format that allows users to record audio or other digital data in such a way that the recording is permanent (nonerasable) and may be read indefinitely. Derived from compact-disk recordable. Also known as compact-disk write-once (CD-WO).



(1) (Call Detail Reporting) See call accounting.

(2) (Common Data Rate) The standard 13.5 MHz sampling rate for 480i and 576i digital video systems. See ITU-R BT.601 and CIF.

(3) (Compact Disc-Recordable) A type of CD disc that can be recorded, but not erased. Used to back up and transfer data and to master CD-ROMs, CD-R discs can be written ("burned") and read by most CD/DVD drives. The phrase "burn a CD" really means "burn a CD-R."

The most common CD-R formats hold 650MB (74 minutes) of data or 700MB (80 min.). Also available are 550MB (63 min.), 790MB (90 min.) and 870MB (99 min.), the latter two being non-standard. The higher capacities are achieved by reducing the distance between tracks (track pitch). To record a full 650MB disc takes only a couple minutes using 40x recorders. For speed ratings of drives, see CD-ROM drives.

Change the Reflectivity
The binary 0s and 1s in CDs and CD-ROMs are actual pits (or lack thereof called "lands") stamped into the media. CD-Rs create the equivalent of pits and lands by altering the reflectivity of a dye layer. Different dyes are used, including cyanine (green), pthalo-cyanine (yellow-gold) and metal-azo (blue). See CD-RW, multisession, disc-at-once, track-at-once, CD UDF and optical disc.

CD-R Layers
Fresh out of the box, a CD-R disc is entirely reflective, because the dye layer is transparent. In order to create the equivalent of a CD or CD-ROM pit, the laser deforms the dye, making it darker and less reflective. In contrast, CD and CD-ROM pits are molded into the plastic and covered by an aluminum reflective coating (for more details, see CD-ROM).

A Partially Burned Disc
Recording starts at the center and spirals outward. To tell if a CD-R was burned, look for the slight change in reflectivity on the recording side. In this example, only 6% of the disc has been written, and the arrows point to the end of the recorded area (look carefully).

Burning a CD-R
To "burn" a CD-R, the files are dragged and dropped into a recording window as in this Easy CD Creator example. Most software supports audio and data CDs and may also print the cover and inside jacket of the jewel case.