How to Reuse Space.

Can space that is already full be at all useful for computation? While this question may seem trivial, a line of work beginning with Barrington's Theorem [B'89] and a follow-up by by Ben-Or and Cleve [BoC'92] has shown that contrary to our intuition about space-bounded computation, the same memory can in fact be used for multiple unrelated tasks. We will survey the history of this work, with a focus on catalytic computation [BCKLS'14], as well as see some of the techniques that are used to reuse space.