DC100 was a magnetic tape format for data, introduced by Hewlett-Packard in 1975 for data storage in its HP-9825 programmable calculator. Previous magnetic card formats were too limited in capacity, and Compact Cassette was too slow.
HP and 3M developed the DC100 from the larger 3M QIC Data Cartridge, but due to limited production by 3M, HP reverse-engineered the cartridge and improved on the the design so they could manufacture their own cartridges.
DC100 had an uncompressed capacity of 210 KB on a tape length of 140 ft. It used 4mm wide (1/8-inch) tape.