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Background[ edit ] Owing to the marked increase in demand for telephone numbers to be available for allocation since the s, the United Kingdom's telephone numbering system has been restructured several times on both a national and regional level, resulting in several modifications to the way British telephone numbers are written.
As a consequence of these changes, many people were left with a misunderstanding of how the system of area codes and local numbers operates. A standard United Kingdom fixed telephone number i. The STD Subscriber Trunk Dialling code indicates the geographical area of the std meaning business plan, and is dialled before the local number.
For the majority of calls dialled within the same area, the trunk prefix and area code need not be dialled, but are ignored if they are. Specifically, the requirement to dial the full number allowed for numbers to be allocated in which the first digit after the area code begins with a zero or a one.
This change makes aboutnew numbers available for each area code in which the change has been made. Until STD was introduced, only telephone operators could connect calls over the trunks long distance links between major exchanges.
A subscriber would have to dial 0 for the operator and then request a long distance call.
As STD was introduced area by area the meaning of the 0 changed; it was now the trunk prefix used to raise a call automatically to the trunk dialling level, what telephone companies now call a National call.
The new code of was introduced for calling an operator. The leading 0 is not part of an area code,[ citation needed ] which is why international callers dialling into the UK must not dial it. The area code plus local number can have varying total and composite digit lengths, for historical and operational reasons, but as a rule they do not exceed 11 digits in combined length.
Problems may occur for the reader when this spacing or formatting is incorrectly applied by the publisher. London numbers[ edit ] History of the confusion[ edit ] When the UK's original STD codes were allocated in the late s, London was given the code Relatively few subscribers could dial trunk calls, so the 01 code was not generally included as part of the published telephone number.
In the early s London telephones still had exchange names, the first three letters having to be dialled before the four-digit local number, e. ABBey London Transport. In the mids, All Figure Numbers AFNs were introduced in London and five other large cities because the number of meaningful letter combinations was becoming exhausted.
Callers in London were still instructed to dial only the seven digits those after the hyphen when calling other London numbers because an error message would result if the 01 code were dialled.
This restriction was eventually phased out as exchanges were modernised, and the STD code was shown in brackets to standardise with the format used in non-AFN areas, e. Consequently, there potentially then existed two separate numbers, because they were in different area codes, and could also be valid.
The local numbers remained as seven digits.
This doubled the numbers available for London, but it also meant that a person from outer London, when calling a central London number and vice versahad to dial the full number including prefix. At the same time, those five other places gained a brand new x area code.
The town of Reading later gained a new x code as available numbers quickly became scarce after PhONEday, being done in stages between and Reunification[ edit ] Further increased demand for telephone numbers in London led to the need for more number-space: From 1 Junea new code for a re-united London was created, All the old seven-digit numbers had a 7 or 8 prefixed to them: After this date, London became once more fully united and all local numbers could be connected correctly from anywhere in the area.
The following diagram shows the history of London's code, starting with the original unified 01 code and ending with the reunified code: Misquoting[ edit ] Although London was divided for only ten years and has since been reunited for much longer, people still frequently quote and write London numbers as if the city and surrounding suburbs were still split up into central and suburban areas by saying and writing "" and "".
On the day of the changeover, one in three callers failed to correctly use eight-digit local dialling. Also, many users are unaware that there is any local dialling procedure,[ citation needed ] probably because of the increasing popularity of mobile phones, from which the full national number must always be dialled.
The incorrectly placed pauses are also heard in speech everywhere: While some clear publicity explaining the change was produced,  BT's directory-assistance service quoted the codes incorrectly and, until Novembertheir online phonebook still incorrectly showed "" as "London Inner" and "" as "London Outer".
Outside London, in the areas that had newly assigned x codes in the s, many mistakenly believed that the added digit necessary to lengthen the subscriber number to seven digits was part of their new area code, largely because these places originally had traditional area codes being non- Director areasand as a result, many misquoted their numbers in the xx xxxxxx format, rather than in the correct x xxx xxxx format.The C++ Core Guidelines are a set of tried-and-true guidelines, rules, and best practices about coding in C++.
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WG21 Number Title Author Document Date Mailing Date Previous Version Subgroup Disposition; SD PL/WG21 document list: John Spicer: