CD

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Related to audio disc: CD-R

CD:

see compact disccompact disc
(CD), a small plastic disc used for the storage of digital data. As originally developed for audio systems, the sound signal is sampled at a rate of 44,100 times a second, then each sample is measured and digitally encoded on the 4 3-4 in (12 cm) disc as a series of
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.

Cd,

symbol for the element cadmiumcadmium
[from cadmia, Lat. for calamine, with which cadmium is found associated], metallic chemical element; symbol Cd; at. no. 48; at. wt. 112.411; m.p. 321°C;; b.p. 765°C;; sp. gr. 8.65 at 20°C;; valence +2.
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.

CD

Abbrev. for Córdoba Durchmusterung. See Bonner Durchmusterung.

Cd

(chemistry)

CD

candela

The International Standard unit of luminous intensity; closely approximates the formerly accepted unit known as the “international candle.”

CD

(1)

cd

(operating system)
change directory.

cd

(networking)
The country code for the Democratic Republic of the Congo (formerly Zaire, zr).

CD

(1) See carrier detect, candela and continuous delivery.

(2) (Change Directory) A DOS/Windows command. See Chdir.

(3) (Compact Disc) An optical digital audio disc that contains up to 74 minutes of hi-fi stereo sound. Introduced in the U.S. in 1983, the disc is a plastic platter (120mm/4.75" diameter) recorded on one side, with individual tracks playable in any sequence. Its storage capacity is from 650MB to 700MB. Other forms of CDs, such as CD-ROM, CD-I and Video CD, all stem from the original Compact Disc-Digital Audio (CD-DA) format. CDs can be played in CD, CD-ROM, CD-R, CD-RW and most DVD drives. For more on how CDs are made, see CD-ROM.

Sound is converted into digital code by sampling the sound waves 44,056 times per second and converting each sample into a 16-bit number. CDs use 1.411 million bits for each second of stereo sound, although this bandwidth requirement is reduced considerably when music compression formats are used (see MP3 and AAC). The tracks are recorded as microscopic pits in a groove that starts at the center of the disc and spirals outward to the edge.

A Note on Terminology
In the early 1990s when CD-ROMs first became popular, "CD" meant music, and "CD-ROM" meant data. Today, "CD" refers to both audio CDs and data CD-ROMs, which also include CD-R and CD-RW media. See CD-ROM and mini CD.

The Books
Documentation for various CD formats are found in books commonly known by the color of their covers.

 Red Book    - CD-DA (Audio)

 Yellow Book - CD-ROM (Data)

 Orange Book - CD-R, CD-RW,
                 Photo CD (Recordable)

 White Book  - VCD (Video)

 Blue Book   - CD Extra (Audio and data)

 Green Book  - CD-I (Interactive)


What Happened to the Phonograph?


The audio CD was introduced in the U.S. in 1983, and within five years, CDs and CD players exceeded the sales of LPs and turntables.

From Carved Sound to Pits
Unlike phonograph records, in which the platter is literally carved with sound waves, CDs are recorded as microscopic pits covered by a clear, protective plastic layer. Instead of a needle vibrating in a groove, a laser shines onto the pits, and the reflections are decoded. Audio CDs, as well as all variations of the CD (CD-ROM, CD-R, etc.) use a spiral recording track like a phonograph record, but start at the center, not the edge. See analog audio.

Better Dynamic Range
Digital sound is cleaner than phonograph records because the numbers are turned into sound electronically. There are no needle pops and clicks and no tape hiss if the original recording was digital. In addition, the CD can handle a wider range of volume. A soft whisper can be interrupted by a loud cannon blast. If a phonograph record were recorded with that much "dynamic range," the needle would literally jump out of the groove.

Too Harsh for Critical Ears?
Pops and clicks aside, from the onset of audio CDs, many critics claimed digital sound was harsh and not as musical as the vinyl platter. DVD-Audio and SACD, two advanced digital formats with superior sound quality, came out in 1999, but neither one became popular (see DVD-Audio and SACD). See high-resolution audio.

In the meantime, turntables and vinyl records are still manufactured, although in smaller quantities, and this legacy industry is expected to persist. See turntable, laser turntable and USB turntable.
References in periodicals archive ?
When recovering unreadable files from audio discs, CD/DVD Diagnostic shows you the Recorder Identification (RID), the International Standard Recording Code (ISRC) and its information about the recording studio and publisher, and the CD text, including the album, track, and artist names.
Like all DVD players, both machines play DVD video and audio discs, as well as all CDs.
A High Resolution Blu-ray Audio Disc featuring all 62 tracks in both stereo and 5.
CD players designed to play audio discs may apply this MultiPlay logo to signify that they are capable of audio playback on CD-R and CD-RW discs as well.
Digital Audio Disc was incorporated in 1983 and turned out its first CD a year later.
ArcSoft TotalMedia(TM) combines a variety of program-specific features such as TV recording, DVD authoring, photo editing, and audio disc creation into one easily accessible package.
The pictures and the audio discs complement the total effect.
A limited run of the audio discs are available in the Ann Arbor and Auburn Hills area.
Paul Wellings' home in Bilston, near Wolverhampton, was subsequently raided and sophisticated equipment used to produce fake video and audio discs was seized.
This equipment will allow to record text information on audio discs and then to listen them.
court the way in terms of audio, making and releasing audio discs on a timely basis when arguments are finished.
For three decades, Richard and Jean, of Riddon Drive, Hinckley, have tirelessly organised support meetings and published a newsletter every two months, sent audio discs out to members, organised outings and fundraising events.