21. It had a magnetic drum memory of rotating at and could invert a square matrix of order 25 in half an hour. 22. The program was stored as a bit image on a continuously running magnetic drum , and loaded in a fraction of a second. 23. The use of a magnetic drum for memory meant that computer programs also had to be interleaved with the rotations of the drum. 24. BRLESC employed punched cards, magnetic tape, and a magnetic drum as input-output devices, which could be operated simultaneously. 25. Routing information would be placed on the magnetic drum , which could store thousands of routes and could be easily changed on demand. 26. Like all early main-frame systems, this batch-oriented system managed magnetic drums , disks, card readers and line printers. 27. Although Rand kept the ERA team together and developing new products, it was most interested in ERA's magnetic drum memory systems. 28. The company that manufactured the rotating magnetic drum part of the Speaking Clock was Roberts & Armstrong ( Engineers ) Ltd of North Wembley. 29. Backing store was magnetic drum and optionally one-inch-, half-inch-or quarter-inch-wide magnetic tape. 30. Since a magnetic drum does not support random access, some time is lost waiting for an instruction or piece of data become available.
