A CD or compact disc player is a modern electronic device that plays audio from compact discs. They are played in home stereo systems, car audio systems and PCs, besides also being available as handheld devices.

The basic job of the CD player is to find and read the data stored as bumps on the device. Because these bumps are so minute the CD player is a very precise piece of engineering. It is comprised of three basic components: a drive motor that spins the disc; a laser and lens system that read the bumps; and a tracking mechanism that moves the laser assembly so that the beam can then follow the spiral track.

The CD player is the result of a good deal of computer technology that forms the data into data blocks and sends them either to the DAC of an audio CD or to the computer of a CD-ROM drive.

When the CD player focuses the laser on the track of the bumps, the laser beam passes through a layer of polycarbonate, reflects off an aluminum layer and then hits an opto-electronic device that is so sensitive that it easily detects any changes in light. The bumps show up light differently than the aluminum layer, and the opto-electronic device registers changes in reflectivity that help the device read the bits that constitute the bytes.

However, the CD player’s toughest job is to keep the laser beam centered on the data track. As the tracking system plays the CD, it moves the laser outward continually, making the bumps move past the laser at a higher speed. CDs can be stored in a variety of formats of which the two most popular are CD-DA for audio and CD-ROM for computer data.