The random-access memory accounting machine - II. The magnetic-disk, random-access memory (Reprinted from IBM Journal of Research and Development, vol 1, 1957)

The IBM Type 350 magnetic disk, RAM used in the RAM accounting machine (RAMAC) system is a large-capacity storage device with relatively rapid access to any record. The information is stored magnetically on fifty rotating disks. The disks are chosen for the recording medium because they have a good volumetric efficiency for surface storage. Magnetic recording is chosen because of both its permanence and ease of modification, while it still allows good storage density.