Flip-flops are digital logic devices that synchronize changes in output state (1 or 0) according to a clocked input. Because they use sequential logic, flip-flops control and are controlled by other circuitry in a specific sequence that is determined by both a control clock and enable/disenable control signals. Several types of flip-flops are available. D flip-flops have one data input (D) and two outputs (Q and Q’). S-R flip-flops have either set (S) and reset (R) inputs, or set (S) and clear (C) inputs. Depending on the input values, the two complementary outputs (Q and Q’) change according to the device’s logical function at the moment of the clock input’s active transition. Active high and active low S-R flip-flops are available. J-K flip-flops, a type of S-R device, define the flip-flop’s indeterminate state. Toggle or T flip-flops, a single input version of the J-K flip-flop, toggle the output with each clock pulse. Typically, T flip-flops are used to develop counters, registers, and similar devices.