A flip-flop is not what you probably thought it was:
http://en.wikipedia.org/wiki/Flip-flop
Note that in Wikipedia (or any other search engine), a flip-flop is NOT programming logic to turn a device on or off. What you see are the popular sandals that make the flip and flop noise when you walk, and even the s_e_x-position-movement by gay men, but no programming logic!
The only place Google finds "flip-flop" used erronously to refer to PLC logic . . . is on this site. How can we be so out-of-touch with the rest of the world? It must be from working in windowless rooms with our heads stuck in a monitor for too many years.