The first non-volatile memory that was widely used. Core storage held magnetic charges in tiny ferrite cores, and the direction of the flux determined the 0 or 1. Developed in the late 1940s by Jay W. Forrester and Dr. An Wang, core storage was used extensively in the 1950s and 1960s as the computer's internal workspace until it was replaced with semiconductor memory.
The cores (bits) were written by sending pulses with half the maximum current down each of the X and Y wires that intersected at that core location. The direction of the pulses determined the magnetization (0 or 1). The core that received both pulses was changed because it received more than half the current. Reading was accomplished by a "destructive" read. A "0" was written to the core, and if the core was already a 0, the sense wire received no current. If it was a 1, current was sensed. The final step to complete the read was to rewrite the bit.
In 1956, IBM paid Dr. Wang $500,000 for his patent on core memories, which he used to expand his company, Wang Laboratories. See non-volatile memory
and early memory
Core storage is why the internal workspace of the computer is called "memory." The cores held their content without power. It did remember.
Cores from the Whirlwind Computer
In 1952, this Whirlwind I core plane held 256 bits. Today's memory chips hold billions of bits in that same amount of space. (Images courtesy of The MITRE Corporation Archives.)