Editing Computability theory (section)

===Numberings===
A numbering is an enumeration of functions; it has two parameters, ''e'' and ''x'' and outputs the value of the ''e''-th function in the numbering on the input ''x''. Numberings can be partial-computable although some of its members are total computable functions. [[Admissible numbering]]s are those into which all others can be translated. A [[Friedberg numbering]] (named after its discoverer) is a one-one numbering of all partial-computable functions; it is necessarily not an admissible numbering. Later research dealt also with numberings of other classes like classes of computably enumerable sets. Goncharov discovered for example a class of computably enumerable sets for which the numberings fall into exactly two classes with respect to computable isomorphisms.