Editing Complexity class (section)

===Basic definitions===
Complexity classes are often defined using granular sets of complexity classes called '''DTIME''' and '''NTIME''' (for time complexity) and '''DSPACE''' and '''NSPACE''' (for space complexity). Using [[big O notation]], they are defined as follows:
* The time complexity class <math>\mathsf{DTIME}(t(n))</math> is the set of all problems that are decided by an <math>O(t(n))</math> time deterministic Turing machine.
* The time complexity class <math>\mathsf{NTIME}(t(n))</math> is the set of all problems that are decided by an <math>O(t(n))</math> time nondeterministic Turing machine.
* The space complexity class <math>\mathsf{DSPACE}(s(n))</math> is the set of all problems that are decided by an <math>O(s(n))</math> space deterministic Turing machine.
* The space complexity class <math>\mathsf{NSPACE}(s(n))</math> is the set of all problems that are decided by an <math>O(s(n))</math> space nondeterministic Turing machine.