A magnetic-tape auxiliary storage system for the Edsac

A description is given of an auxiliary storage system using magnetic tape which has been operated experimentally on the Edsac. The tape transport system uses pneumatically operated capstans and is capable of traversing tape in either direction at a speed of 100in/sec; the starting and stopping times are about 10 millisec. The tape reels are controlled by photo-electrically operated servo systems. The motion of the tape, and the action of reading and writing, are controlled by instructions added for the purpose to the Edsac instruction code, and a detailed discussion is given in the paper of the way in which subroutines for transferring blocks of information to and from the tape may be written.