Editing Twistor memory (section)

===Construction===
[[File:Coincident-current magnetic core.svg|thumb|left|Diagram of a 4×4 plane of magnetic-core memory in an X/Y line coincident-current setup. X and Y are drive lines, S is sense, Z is inhibit. Arrows indicate the direction of current for writing.]]
In core memory, small ring-shaped [[magnet]]s - the cores - are threaded by two crossed wires, ''X'' and ''Y'', to make a matrix known as a ''plane''. When one X and one Y wire are powered, a magnetic field is generated at a 45-degree [[angle]] to the wires. The core magnets sit on the wires at a 45-degree angle, so the single core wrapped around the crossing point of the powered X and Y wires will be affected by the induced field.

The materials used for the core magnets were specially chosen to have a very "square" [[magnetic hysteresis]] pattern. This meant that fields just below a certain threshold will do nothing, but those just above this threshold will cause the core to be affected by that magnetic field; it will abruptly flip its magnetization state. The square pattern and sharp flipping states ensures that a single core can be addressed within a grid; nearby cores will see a slightly different field, and not be affected.