Editing Magnetic-core memory (section)

====Reading====
To read a bit of core memory, the circuitry tries to flip the bit to the polarity assigned to the 0 state, by driving the selected X and Y lines that intersect at that core.

* If the bit was already 0, the physical state of the core is unaffected.
* If the bit was previously 1, then the core changes magnetic polarity. This change, after a delay, induces a voltage pulse into the Sense line.

The detection of such a pulse means that the bit had most recently contained a 1. Absence of the pulse means that the bit had contained a 0. The delay in sensing the voltage pulse is called the '''access time''' of the core memory.

Following any such read, the bit contains a 0. This illustrates why a core memory access is called a ''destructive read'': Any operation that reads the contents of a core erases those contents, and they must immediately be recreated.