A memory cell is a type of information storage circuit useful in many patterns that perform complex logical operations. Most commonly a memory cell can store a single bit of information; see for example demultiplexer, honey bit, and boat-bit. Depending on the application, the circuit may be a toggle circuit or a permanent switch, or it may be possible to send one or more signals to set the circuit to a "1" state, as can be done with a keeper mechanism. In that case a different input signal must be used to test the current state, usually with a destructive read reaction.
A more complicated example can be found in the O(sqrt(log(t))) pattern, which destructively reads a growing 2-dimensional array of minimal memory cells. Each memory cell may either contain a boat (below left) or empty space (below right), with no permanent circuitry anywhere near:
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The two beehives and the block are placed by slow salvos, after an initial 90-degree 2-glider collision that produces a target honey farm. The beehive constellation acts as a one-time turner for an incoming glider. If the boat is present, it acts as a second one-time turner for that glider, sending back a "1" signal. The "backstop" block in the northeast is destroyed cleanly in either the "0" or the "1" case.