An archetypal dumb embedded-systems application, like toaster
(which superseded it).
During one period (1983--84) in the deliberations of ANSI X3J11 (the C standardisation committee) this was the canonical example of a really stupid, memory-limited computation environment.
"You can't require "printf(3)" to be part of the default run-time library - what if you're targeting an elevator controller?"
Elevator controllers became important rhetorical weapons on both sides of several holy wars