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Computer science Definition

Theory of computation

Builds on Model of computationDecision problem

Definition

The theory of computation is the branch of mathematics and theoretical computer science that studies the following questions about a model of computation.

  1. Which decision problems and functions can be solved by a machine of the model at all; this is computability theory.
  2. How many resources, such as time and memory, a solution needs; this is computational complexity theory.
  3. What restricted machines, such as finite automata, can recognise; this is automata theory.

Remarks

Example: the result that no Turing machine solves the halting problem belongs to the theory of computation, in its first part. Non-example: the design of a faster processor chip is not part of the theory, because it concerns physical hardware and not what an abstract model can compute. The answers to the first question do not depend on the choice among the usual models, since these are all equivalent in power. The answers to the second question depend on the model, but only up to polynomial factors among the usual deterministic models.

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To understand this page from the ground up, read these 3 pages in order. The foundations come first.

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  1. Decision problem concept
  2. Model of computation concept
  3. Theory of computation definition

Further reading

  1. Web https://en.wikipedia.org/wiki/Theory_of_computation
About this page
TagQXZ8X4CWGS
URIm2://QXZ8X4CWGS
Kinddefinition
WritingW0 stub
MSC68Q01, 03D10
DefinesTheory of computation
UsesModel of computation, Decision problem
Changed3 November 2026

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