Audio cassette
Some early home computers, such as the Commodore 64, used cassettes to store data or computer programs. Some cassettes were marketed specifically for data, although these cassettes were not physically different from those used for audio. Software and games were also sold on cassettes. In the late 1980s, higher-capacity tape formats, floppy disks, and CD-ROMs made this usage of the cassette obsolete. Another format called D/CAS (Data Cassette), sometimes called a streamer cassette, was also available. It was based on the audio cassette, but it had a different formulation of tape that was designed for data only, and used a special tape drive that was incompatible with normal cassettes. It could store up to 600 MB of data. Unlike normal cassettes, it had only one side.