A datassette is simple to use and a popular storage device amongst beginners. While datassettes are cheaper than a disk drive, the data transfer is very slow (~60 - 70 bytes/s), although higher transfer rates can be achieved with fast loaders (up to ten times more).
The datassette has its own cable permanently attached to it, carrying both data and the power needed for the unit. This cable connects to the datassette connector (square; 12-pins, with underparts 8 : 4) at the C64. The datassette accepts standard cassette tapes, and a 90-minutes tape (45 minutes on each side) will hold on the order of 150 kilobytes on each side if no compression or fast loader is used.