corresponding read head. Under normal operation, data are written back without change, but this data flow can be intercepted at any time, allowing the machine to update sections of a track as needed.

This arrangement allows the designers to create "delay lines" of any desired length. In addition to the twenty "long lines" of 108 words each, there are four more short lines of four words each. These short lines recycle at 27 times the rate of the long lines, allowing fast access to frequently needed data. Even the machine's accumulators