Numbering scheme in the context of "Computability theory"

A telephone numbering plan is a type of numbering scheme used in a telecommunications network to assign telephone numbers to subscriber telephones or other telephony endpoints. Telephone numbers are the addresses of participants in a telephone network, reachable by a system of destination code routing. Telephone numbering plans are defined world-wide, as well as within each of the administrative regions of the public switched telephone network (PSTN), and in private telephone networks.

In public numbering systems, geographic location typically plays a role in the sequence of numbers assigned to each telephone subscriber. Many numbering plan administrators subdivide their territory of service into geographic regions designated by a prefix, often called an area code or city code, which is a set of digits forming the most-significant part of the dialing sequence to reach a telephone subscriber. Within such regions designated by area codes, locally unique telephone numbers are assigned based on locally determined principles but in agreement with the larger-network rules.

In Great Britain, there is a numbering scheme used to classify and identify all roads. Each road is given a single letter (representing a category) and a subsequent number (between one and four digits). Though this scheme was introduced merely to simplify funding allocations, it soon became used on maps and as a method of navigation. There are two sub-schemes in use: one for motorways, and another for non-motorway roads.

While some of Great Britain's major roads form part of the international E-road network, no E-routes are signposted in the United Kingdom. Due to changes in local road designation, in some cases roads are numbered out of zone. There are also instances where two unrelated roads have been given exactly the same number; for example, the Leicester Ring Road and a road in Cumbria are both designated A594.

The Enzyme Commission number (EC number) is a numerical classification scheme for enzymes, based on the chemical reactions they catalyze. As a system of enzyme nomenclature, every EC number is associated with a recommended name for the corresponding enzyme-catalyzed reaction.

EC numbers do not specify enzymes but enzyme-catalyzed reactions. If different enzymes (for instance from different organisms) catalyze the same reaction, then they receive the same EC number. Furthermore, through convergent evolution, completely different protein folds can catalyze an identical reaction (these are sometimes called non-homologous isofunctional enzymes) and therefore would be assigned the same EC number. By contrast, UniProt identifiers uniquely specify a protein by its amino acid sequence.