Magnetic-core memory stores data on small ferromagnetic rings which can be magnetised clockwise or anticlockwise to represent a 0 or 1 bit. Reading a bit also erases it, making it necessary to immediately restore the data with a rewrite cycle. The rings are threaded on a grid of wires, X and Y to select a bit, sense to read and inhibit to write. The first core memory was installed on the MIT Whirlwind I in 1953. The name of Core War was inspired by magnetic-core memory.

early magnetic-core memory