Introduction:
Mealy and Moore machines are two types of finite state machines that are used in digital systems to model sequential logic. They differ in their output variations, which is the major difference between the two.

Mealy Machine:
- A Mealy machine is a type of finite state machine where the outputs depend on both the current state and the inputs.
- The output of a Mealy machine is associated with the transitions between states, rather than just the states themselves.
- The output of a Mealy machine changes immediately after a transition occurs, based on the current state and the input that caused the transition.
- The output is not stored in the states, but rather in the transitions between states.

Moore Machine:
- A Moore machine is another type of finite state machine where the outputs only depend on the current state.
- The output of a Moore machine is associated with the states themselves, rather than the transitions between states.
- The output of a Moore machine remains constant throughout the duration of a state and only changes when a transition occurs.
- The output is stored in the states and is not directly affected by the inputs.

Comparison:
Output Variations:
- The major difference between Mealy and Moore machines is the way they handle output variations.
- In a Mealy machine, the outputs can change immediately after a transition occurs, as they are associated with the transitions themselves.
- In a Moore machine, the outputs remain constant throughout the duration of a state, only changing when a transition occurs.
- Mealy machines have more flexibility in terms of generating outputs, as they can produce different outputs for the same input sequence depending on the current state.
- Moore machines, on the other hand, have more predictable outputs as they are solely determined by the current state.

Conclusion:
The major difference between Mealy and Moore machines is the way they handle output variations. Mealy machines generate outputs based on both the current state and the inputs, while Moore machines generate outputs solely based on the current state. Mealy machines provide more flexibility in terms of output generation, while Moore machines offer more predictable outputs.