Flip-flops are devices used in the digital field for a variety of purposes. When properly connected, flip-flops may be used to store data temporarily, to multiply or divide, to count operations, or to receive and transfer information.
Flip-flops are bistable multivibrators. The types used in digital equipment are identified by the inputs. They may have from two up to five (or more) inputs depending on the type. They are all common in one respect. They have two, and only two, distinct output states. The outputs are normally labeled Q and Q (or ¬Q) and should always be complementary. When Q = 1, then Q = 0 and vice versa.
In this section we will discuss four types of flip-flops that are common to digital equipment. They are the R-S, D, T, and J-K flip-flops.