Prof. Dr. Thorsten Jungmann (last updated 2026-10-03)
George H. Mealy (1927–2010) was an American mathematician and computer scientist. He studied at Harvard University and graduated in 1951 with an A.B.; at that time he began working for Bell Laboratories. Later he worked at the RAND Corporation and then at IBM, and he taught at Harvard. He was also a co-developer of the programming language IPL-V and an early advocate of macro processors in assembly language programming.
The Mealy machine (German: Mealy-Automat) is named after him. It is a finite state machine whose output values are determined both by its current state and by the current inputs. In the state diagram of a Mealy machine an output value is associated with each transition, in contrast to the Moore machine, whose outputs depend solely on the current state. Mealy presented the concept in 1955 in the paper ‘A Method for Synthesizing Sequential Circuits’, published in the Bell System Technical Journal.
When implemented as electronic circuits, Mealy machines tend to have fewer states than Moore machines and react faster to inputs: they react in the same cycle and do not need to wait for the clock. The price is that an input change can cause an output change as soon as the logic is done, so asynchronous feedback may occur when two machines are interconnected. Moore machines are regarded as safer in this respect, because their outputs change at the clock edge.
Reference and further reading:
https://en.wikipedia.org/wiki/George_H._Mealy
https://en.wikipedia.org/wiki/Mealy_machine