An obsolete storage device in which the data was stored as a charge pattern within a cathode-ray tube and could be read by a scanning beam of electrons. The data was not usually visible. One of the early designs was the Williams-tube store, developed by F. C. Williams of the University of Manchester, UK; it was one of the earliest forms of random-access memory. Electrostatic storage was used on a number of first-generation computers (Ferranti Mark I, Whirlwind, IBM 701, IAS). It gave a significant reduction in storage cost compared to the mercury delay line memory, but the information had to be frequently regenerated (rewritten) and was lost when power was removed. It was displaced in processor designs in the mid-1950s by core stores.