Memory Devices
Memory elements exist indefinitely in one of two possible states,
Binary data are stored in a memory element by placing the element into the 0 state to store a 0 and into the 1 state to store a 1.
The output Q of the circuit indicates the present state of the memory.
The two memory element types most commonly used in switching circuits are latches and flip-flops.
Latches are devices whose excitation inputs control the state of the device.
A flip-flop differs from a latch in that it has a control switch called a clock. This means a flip-flop waits for its clock signal before changing states. The final state of a flip-flop is determined by its excitation values at the time the clock signal occurs.