Definition: core storage

The first widely used memory. Core storage held magnetic charges in tiny ferrite cores, and the direction of the flux determined the 0 or 1. However, the value of the bit (core) remained after power was removed.

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 chips. In 1956, IBM paid Dr. Wang $500K for his patent, which he used to expand his company (see Wang Labs).

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.

Part of the Confusion
The terms storage and memory are mixed up to this day and one of the reasons was core memory. Toshiba's naming of its storage chip "flash memory" was another. Because core memory retained its content, it functioned like storage (see storage vs. memory). See non-volatile memory, memory chip and early memory.

Core Storage

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. See Whirlwind. (Images courtesy of The MITRE Corporation Archives.)