this category. Other storage tubes were able to store greyscale/halftoned images; the tradeoff was usually a much-reduced storage time. Some pioneering storage tube displays were MIT Project MAC's ARDS (Advanced Remote Display Station), the Computek 400 Series Display terminals (a commercial derivative), which both used a Tektronix type 611 storage display unit, and Tektronix's 4014 terminal, the latter becoming a de facto computer terminal standard some time after its introduction (later being emulated by other systems due to this status). The first generalized computer assisted instruction system, PLATO I, c. 1960 on ILLIAC I, used a storage tube as its computer graphics display. PLATO II and PLATO III also used storage tubes as displays. See also Direct-View Bistable Storage Tube (DVBST) Cathode ray tube (for an explanation of how analog storage tubes worked) Williams tube and Selectron tube both used the term "storage tube" for early computer memory devices Electronic paper References Vacuum tube displays