In the late 1970s, quantum leaps in technology and innovation led to the birth of mass-produced digital music. Pioneers in the electronics industry, excited by laserdisc technology that allowed for high quality video and audio to co-exist on a portable disc, set about to create something similar for the music industry. Dismayed by the bulky size of a laserdisc, those working on the music project set about to create a more user-friendly and affordable high end product: the compact disc. CDs store audio in a stereo format known as 16-bit PCM. When played back through a stereo system, uncompressed PCM sound creates a clear hi-fidelity sound without any of the analog "hiss" commonly found on records and cassettes. When an album is recorded in a pure digital format without post-recording analog mixing, the CD will be labeled with the symbol "DDD" to indicate purely digital production. For recordings made before the digital era, you will find CDs labeled "ADD" to indicate analog source material that has been digitally mixed and published. Almost all CDs recorded today are in the "DDD" format. CDs also have other features that make them more appealing to than earlier media. CDs can hold over 70 minutes of music, which means more tracks per album. Older albums that may have spanned two records can now fit onto a single CD. CDs also have the ability to house bonus or hidden tracks or even video material that can be played on a home computer. CDs have evolved over the years to include mini-CDs, CD-ROMs, CD-Rs and CD-RWs--all recordable storage discs. While these discs can be used for storing data, they can also be used to create backup copies of your favorite music CDs. Home computers also offer recording programs that let you create playlists and mixes to burn onto your own CD. | 
