An industry standard 74-minute audio compact disk can hold 650 megabytes of data. Other industry standards are the 80-minute, 700 megabyte disks and the 21-minute, 185 megabyte disks. CDs with higher capacity, up to 890 megabytes, exist but don't conform to industry standards and may not work in all readers.
Compact disks come in two standard sizes: 120 millimeters and 80 millimeters, normally called a mini-CD. Compact disks were introduced to the North American and European markets in March 1983 and gained immense popularity almost instantly. With the advent of online music stores such as iTunes, disk usage is in decline as of 2014.