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    A compact disc (CD) is a polycarbonate disc measuring 120 mm in diameter with one or more metal layers capable of storing digital information.  The most prevalent types of compact discs are those used by the music industry to store digital recordings and CD-ROMs used to store computer data. Both of these types of compact disc are read-only, which means that once the data has been recorded onto them, they can only be read, or played.

    CDs deliver their music or other content digitally; a low-power laser reads information on the CD’s metal layer, then converts that digital stream into an audio signal. By contrast, a vinyl LP uses a physical groove that passes vibrations to a sensitive stylus.

    When were CDs invented?

    Introduced in 1982, CDs were co-developed by Sony and Philips as a way to deliver high-quality audio on a small, single-sided medium. The format quickly gained popularity as consumers demanded the high-fidelity music CDs delivered, and manufacturers debuted players for home, auto, and portable use applications.

    At the height of their popularity in the early 2000s, music labels shipped more than 915 million CDs annually. But with the rise of digital streaming platforms, Statisa reports that compact disc shipments totaled just 31 million units.

    How much music or data does a CD hold?

    A compact disc can hold 74 minutes of recorded music or other audio; roughly 3.5 times the length of the standard vinyl record.

    When used to store data, a CD’s maximum capacity is 700MB.

    Can I record on a CD?

    CDs were initial read-only (CD-R or CD-ROM). Beginning in 1988, recordable CDs were introduced that allowed data to be written to the disc either once (CD-R) or multiple times (CD-RW). Recording to the CD-R or CD-RW format required either a specialized audio CD player or a CD burner.