Editing Core rope memory (section)

== Operation ==
Similar to magnetic-core memory, magnetic rings (or cores) are used to determine the data of the software. Unlike magnetic-core memory, the cores themselves are not used to store the data; the way a core is wired controls whether that core represents a '0' or a '1'.

There are three main types of functions a wire can have in core rope memory:

* '''Set/reset:''' These are used to change all of the cores from one polarity to another.
* '''Sense:''' A sense wire can detect a change in a core's polarity. It can pass through a core to indicate one bit state (typically '1') or bypass it to represent the other (typically '0').
* '''Inhibit:''' Inhibit wires are used effectively to address which core to select.

To read from core rope memory, the set/reset wire is given a strong current to change the polarity of the cores. This induces a small voltage on the sense wires passing through them, which can then be used to interpret binary data. The inhibit wires pass a current in the opposite direction of the set/reset wire for all cores but the desired one, acting like a [[Memory address|memory addressing system]]. This prevents the sense wires from detecting polarity changes from the other magnetic cores.

The sense wires are used to encode the data by either going through a core or bypassing it. By using many sense wires, multiple bits of data can be stored for each core. In the case of the Apollo Guidance Computer, each core had 192 sense wires passing through it, which could store 12 16-bit words per core.<ref>{{Cite web |title=Software woven into wire: Core rope and the Apollo Guidance Computer |url=http://www.righto.com/2019/07/software-woven-into-wire-core-rope-and.html |access-date=2024-03-20}}</ref>