Data store for a microcomputer system

A non-volatile, on-line, mass data store is provided that is based on the use of magnetic tape loops 3 housed in magazines 1 readily inserted and removed from an associated tape transport. In order to facilitate the construction of the magazine 1, the latter is provided with only one moving part, namely a backing roller 11 against which the tape is pressed by a rotary drive member 19 of the tape transport during operation of the latter. The rotary drive member 19 is mounted on a solenoid-actuated carriage 21 which is moved between inoperative and operative positions by a solenoid 23. Data is written to, and read from, the tape loop 3 in byte-wide form by a multitrack read/write head 17 that also lays down a taming track on the tape 3.