Computation is a general term for any type of information processing. This includes phenomena ranging from human thinking to calculations with a more narrow meaning. Computation is a process following a well-defined model that is understood and can be expressed in an algorithm, protocol, network topology, etc. Computation is also a major subject matter of computer science: it investigates what can or cannot be done in a computational manner.
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Computation can be classified by at least three orthogonal criteria: digital vs analog, sequential vs parallel vs concurrent, batch vs interactive.
In practice, digital computation is often used to simulate natural processes (for example, Evolutionary computation), including those that are more naturally described by analog models of computation (for example, Artificial neural network). In this situation, it is important to distinguish between the mechanism of computation and the simulated model.
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, 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.
In the theory of computation, a diversity of mathematical models of computers have been developed. Typical mathematical models of computers are the following:
The word computation has an archaic meaning (from its Latin etymological roots), but the word has come back in use with the arising of a new scientific discipline: computer science.
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Computation by |
For my first twenty years, since yesterday,
I scarce believed thou couldst be gone away;
For forty more I fed on favours past,
And forty on hopes that thou wouldst they might
last;
Tears drown'd one hundred, and sighs blew out two;
A thousand, I did neither think nor do,
Or not divide, all being one thought of you;
Or in a thousand more, forgot that too.
Yet call not this long life; but think that I
Am, by being dead, immortal; can ghosts die?
The Theory of Computation is a branch of Mathematics. Generally it is seen as belonging to Computer science. The field of study of this subject is to see if a certain problem can be solved by a computer. If this is the case, then the question is to know if it can be solved in an efficient way.
There are two major branches in it. The first is computability theory. It looks to see if a certain problem can be solved by a computer. Since this is a theoretical field of study, no real computers are used. They are replaced by a system called the Turing machine.
Once it is known if such a solution exists, computer scientists want to know if it can be found, and perhaps how it can be improved. This field of study is covered by the complexity theory. That theory has developed concepts to compare different methods of solving a problem to one another. Such methods are usually called algorithms. This is similar to comparing cooking recipes and seeing which of two recipes is easier to do.
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