Similar to a CRT, electrostatic storage tubes used in the Whirlwind computer in 1950 held a whopping 256 bits each. The bits were "painted" on the surface of the tube, and their electrostatic charges determined their content. See Williams tube. (Image courtesy of The MITRE Corporation Archives.)
Delay Line Memory
In the late 1940s and early 1950s, the memory in the EDSAC and UNIVAC I was made of tubes of liquid mercury that were several feet long. Electrical pulses were converted to sound and back to electrical in a continuous loop. The conversion to sound, which propagates much slower than electricity, slowed down the digital data a fraction of a second and caused the device to function as storage. See EDSAC and UNIVAC I.
Magnetic Drum Memory
This magnetic drum unit was the memory in the IBM 650 computer, introduced in 1954. It held two thousand 10-digit words. That much memory today would fit on the head of a pin, and a very thin pin to be sure. See 650. (Image courtesy of the Hagley Museum and Library.)
Magnetic Core Memory
Two years later, the tubes (above) in the Whirlwind were replaced with magnetic cores, which were far more reliable. The direction of the magnetic energy in the core determined the 0 or 1. Like the tubes, these core planes held 256 bits. See core storage. (Image courtesy of The MITRE Corporation Archives.)
Learn more about early memories