Magnetic core memory
Magnetic core memory, or ferrite-core memory, is an early form of computer memory. It uses small magnetic ceramic rings, the cores, to store information via the polarity of the magnetic field they contain.
The earliest work on core memory was carried out by the Shanghai-born American physicist, An Wang, who created the pulse transfer controlling device in 1949. The name referred to the way that the magnetic field of the cores could be used to control the switching of current in electro-mechanical systems. Wang was working at Harvard University's Computation Laboratory at the time, but unlike MIT, Harvard was not interested in promoting inventions created in their labs. Instead Wang was able to patent the system on his own.
Core arrays were manually assembled; the work was performed under microscopes and required fine motor control. Initially garment workers were used.