The CD – which is short for Compact Disc – started a real revolution in the audio world by making digital audio accessible to a wider public, beginning in the year 1982. A CD is a digital optical disc that can store around 700 MB of data. CDs were originally developed for musical purposes but were quickly adapted to store data as well. Since the 700 MB limit exceeded the storage capacity of hard drives at that time, CDs were very popular for all kind of data storage, so much so that around 200 billion CDs have been sold as of the year 2007. In the early CD era only CD-ROMs – Read Only Memory – were available but in the 90s it became possible for consumers to write their own CDs using a CD burner and a dedicated CD-R or CD-RW.