The transfer-track method of magnetic-drum operation

Differences between digital computers and data-handling machines are discussed and the requirements these place on magnetic-drum stores are examined. In some data-handling machines the information stored on the drum is read out from each track, passed through an arithmetical circuit and written in again during every revolution. Previous methods of doing this are explained and their advantages and limitations are discussed. The transfer-track method is then introduced. In this method, information is read from a first track and written into a second track, via an arithmetical circuit, on alternate revolutions of the drum. During the intervening revolutions the information is read from the second track and written into the first track via the same arithmetical unit. The construction of the drum and amplifiers used can be simple, and only one head per track is required. If the periodicity with which the stored information is required to be modified is less than that of the drum revolutions, one transfer track and arithmetical circuit can be shared by several storage tracks. Arithmetical processes for use with the method are discussed. Details are given of practical reading, writing and switching circuits for use with the method.