Storage medium is a term used to describe the physical material on which digital data is stored. Microfilm is a storage medium consisting of a roll of photographic film containing digital information that can be read using a microfilm reader. A DISK is a flat, round storage medium made of metal, plastic, or paper that is used to store digital data. A CD-ROM is a type of optical disc storage medium that stores digital data and can be read by a computer with an optical drive.