Frederic C. Williams

It held each bit as a charged dot on a cathode ray tube screen, read back through a metal plate and refreshed regularly.

Frederic Williams and Tom Kilburn stored each binary digit as a tiny electric charge on the face of a cathode ray tube. A dot drawn on the screen leaves a positive charge surrounded by a negatively charged area, and a metal plate at the face of the tube picks up a voltage pulse that lets the computer read the stored bit back. Because the electron beam can be pointed at any spot on the screen, any stored bit could be reached directly, which is random access. The charge slowly leaks away, so it had to be rewritten on a regular cycle. Williams first showed the storage of a single bit at the Telecommunications Research Establishment in October 1946. After he moved to Manchester University, he and Kilburn stored 2,048 bits in late 1947, and in 1948 the Manchester Baby used this tube storage to run the first program on an electronic stored-program computer. Sources and later writers call the device the Williams tube or the Williams-Kilburn tube.