Difference Between Mealy Machine and Moore Machine Last Updated : 11 Jul, 2025 Comments Improve Suggest changes 91 Likes Like Report In theory of computation and automata, there are two machines: Mealy Machine and Moore Machine which is used to show the model and behavior of circuits and diagrams of a computer. Both of them have transition functions and the nature of taking output on same input is different for both. In this article, we will learn about Mealy and Moore Machines with their diagrams and the differences between them. What is Mealy Machine?Mealy Machine is defined as a machine in the theory of computation whose output values are determined by both its current state and current inputs. In this machine at most one transition is possible. It has 6 tuples: (Q, q0, ∑, ▲, δ, λ’) Q is a finite set of states q0 is the initial state ∑ is the input alphabet ▲ is the output alphabet δ is the transition function that maps Q×∑ → Q ‘λ’ is the output function that maps Q×∑→ ▲ The diagram is as follows:Moore MachineMoore's machine is defined as a machine in the theory of computation whose output values are determined only by its current state. It has also 6 tuples(Q, q0, ∑, ▲, δ, λ) Q is a finite set of states q0 is the initial state ∑ is the input alphabet ▲ is the output alphabet δ is the transition function that maps Q×∑ → Q λ is the output function that maps Q → ▲ Diagram:Difference Between Mealy Machine and Moore MachineState machines like Mealy and Moore are fundamental in digital design and automata theory. To truly grasp the differences and applications of these machines, join the GATE CS Self-Paced Course. It offers detailed lessons on finite automata and their practical uses, perfect for GATE aspirants. The differences between the Mealy machine and Moore machine is as follows: Moore MachineMealy Machine Output depends only upon the present state. Output depends on the present state as well as present input. Moore machine also places its output in the state.Mealy Machine places its output on the transition.More states are required. Less number of states are required. Moore machines requires more hardware requirement for circuit implementation. Mealy Machines requires less hardware requirement for circuit implementation. They react slower to inputs(One clock cycle later). They react faster to inputs. Synchronous output and state generation. Asynchronous output generation. Output is placed on states. Output is placed on transitions. Easy to design. It is difficult to design. If input changes, output does not change, as moore machine is a type of finite state machine where the output is determined solely by the current state, not by the current input.If input changes, output also changes, because in mealy machine output depends on the present state as well as present input.Has more or the same states as that of the Mealy machine.Has fewer or the same states as that of the Moore machine.ConclusionMoore Machine is a finite automata in which output is associated with each state and Mealy Machine is a finite automata in which output is associated with each transition. Thus, we have learnt the differences between Moore Machine and Mealy Machine and can now deduce their relationships and can solve them. 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