Memory subsystem
The Babbage Analytical Engine's design employed a collection of axes, each holding 40 decimal digit wheels, as the mechanism for storing data during computations. Reading data from an axis was a destructive operation, resulting in zeros on all of an axis's wheels after the read had completed.
From the 1950s to the 1970s, the preferred technology for digital computer memory was the magnetic core. One bit of core memory is stored in a small toroidal (donut-shaped) ceramic magnet. The cores making up a memory array are arranged in a rectangular grid with horizontal and vertical connecting wires. Writing to a bit location involves producing enough current in the wires connected to the bit location to flip the polarity of the core's magnetic field. A 0 bit might be defined as clockwise magnetic flux circulation within the core and a 1 bit as counterclockwise flux circulation.
Reading a bit from core memory consists of attempting to set the bit to the...
