Computation is any type of calculation that includes both arithmetical and non-arithmetical steps and follows a well-defined model understood and described as, for example, an algorithm.
The study of computation is paramount to the discipline of computer science.
A computation can be seen as a purely physical phenomenon occurring inside a closed physical system called a computer. Examples of such physical systems include digital computers, mechanical computers, quantum computers, DNA computers, molecular computers, microfluidics-based computers, analog computers or wetware computers. This point of view is the one adopted by the branch of theoretical physics called the physics of computation as well as the field of natural computing.
An even more radical point of view is the postulate of digital physics that the evolution of the universe itself is a computation - pancomputationalism.
A classic account of computation is found throughout the works of Hilary Putnam and others. Peter Godfrey-Smith has dubbed this the “simple mapping account.”Gualtiero Piccinini's summary of this account states that a physical system can be said to perform a specific computation when there is a mapping between the state of that system to the computation such that the “microphysical states [of the system] mirror the state transitions between the computational states.”