Computation
Computation is any type of calculation^{[1]}^{[2]} that follows a welldefined model understood and expressed as, for example, an algorithm, or a protocol.
The study of computation is paramount to the discipline of computer science.
Contents

Classification 1
 Comparison to calculation 1.1
 Physical phenomenon 2
 Mathematical models 3
 See also 4
 References 5
Classification
Computation can be classified by mainly three unique criteria: digital versus analog, sequential versus parallel versus concurrent, batch versus interactive.
In practice, digital computation aids simulation of natural processes (for example, evolutionary computation), including those that are naturally described by analog models of computation (for example, artificial neural network).
Comparison to calculation
Calculation is a term for the computation of numbers, while computation is a wider reaching term for information processing in general.
Physical phenomenon
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, analog computers or wetware computers. This point of view is the one adopted by the branch of theoretical physics called the physics of computation.
An even more radical point of view is the postulate of digital physics that the evolution of the universe itself is a computation  pancomputationalism.
Mathematical models
In the theory of computation, a diversity of mathematical models of computers have been developed. Typical mathematical models of computers are the following:
 State models including Turing machine, pushdown automaton, finite state automaton, and PRAM
 Functional models including lambda calculus
 Logical models including logic programming
 Concurrent models including actor model and process calculi
See also
 Computing
 Computationalism
 Physical information
 Real computation
 Reversible computation
 Hypercomputation
References
 ^ Computation from the Free MerriamWebster Dictionary
 ^ http://www.answers.com/topic/computation