The Origin of “x” to Close
On Medium, Lauren Archer has tracked the evolution of the use of “x” as a symbol to denote closing a window. While it’s now ubiquitous on both Mac and Windows, it wasn’t a common convention until Windows 95, which in turn picked it up from NeXT, but Archer traces the symbol’s origins even earlier, to Atari’s TOS 1.0 from 1985.