---
tags: [computer-history, memory]
created: Tuesday, September 17, 2024
---

# 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.

![A Williams CRT tube](static/williams-tube.jpg)

![Memory dot pattern from a Williams Tube](static/williams-tube-dots.jpg)
