Williams Tube memory

• One of the early attempts to create RAM in computers based on the EDVAC stored-program architecture.

• Worked by displaying a grid of dots on a cathode-ray tube (“screen”)

• Due to the way CRTs work, this creates a small charge of static electricity over each dot. The charge at the location of each of the dots is read by a thin metal sheet just in front of the display.

• Each dot position could be written to and read from and the pattern was constantly refreshed as the dots would fade over time.