A byte can be stored in a one-bit-wide slice of a nine-track tape, where the extra bit is a parity bit.
All in all, magnetic tapes have the following features:
Storing data on tapes is greatly cheaper than storing data on disks.
Tapes also have large storage capacities, ranging from several gigabytes to a couple of hundred gigabytes.
Accessing data on tapes, however, is much slower than accessing data on disks. Tapes are sequential-access media, which means that to get to a particular point on the tape, the tape must go through all the preceding points. In contrast, disks are random-access media because a disk drive can access any point at random without passing through intervening points.
Because tapes are so slow, they are generally used only for long-term storage and backup. Data to be used regularly is almost always kept on a disk. Tapes are also used for transporting large amounts of data.
