Memory can store only one bit of binary data. The Bistable Mulitvibrator circuit meets the requirements for sorting zero or binary one, since it has two stable states. The stored data stays in the memory element for as long as the power is maintain to the circuit. When the power is switched off the data installed in the memory will be reset. The RS flip flops are classified into two types: the level activated RS flip flop, and the clocked activated RS flip flop. The level activated RS flip flop is sometimes called latch, can be implemented using NAND or NOR gates. The NAND latch is also constructed using NAND gates.

Clocked RS flip flop are clocked activated flip flops. They are also called Gated Latch Circuits. The D- type flip flop can also be group into level activated and clocked activated and has two to three inputs: the D and E input.

The most versatile and widely used flip flop is the JK flip flop. It is because of its operation, which is capable of performing the function of the RS flip flop, the D-flip flop and the other mode of operation which cannot be done by other memory elements like toggling mode. This mode of operation is very useful in designing binary counter circuits.

The T flip flop is similar to JK flip flop configured in the toggling mode operation. The output of the T flip flop complements every time a clock pulse is applied to its input.

Figure 1: The NAND Latch

Figure 2: NOR Latch

Figure 3: D FlipFlop