A room number is a number assigned to a room within a building

Building

In architecture, construction, engineering, real estate development and technology the word building may refer to one of the following:...

. Its purpose is to identify a particular room

Room

A room is any distinguishable space within a structure.Room may also refer to:* Room , by Emma Donoghue* Room, Nepal* Room for PlayStation Portable, a social networking service* Thomas Gerald Room , Australian mathematician...

, and help visitors locate that room. Room numbers may consist of three digits

Numerical digit

A digit is a symbol used in combinations to represent numbers in positional numeral systems. The name "digit" comes from the fact that the 10 digits of the hands correspond to the 10 symbols of the common base 10 number system, i.e...

, but can be any number of digits.

The room number is generally assigned with the first digit indicating the floor

Storey

A storey or story is any level part of a building that could be used by people...

 on which the room is located. For example, room 412 would be on the fourth floor of the building; room 540 would be on the fifth floor. Buildings that have more than ten floors will have four digits assigned to rooms beyond the ninth floor. For example, room 1412 would be on the 14th floor.

The second digit may represent the wing, or section, of the building in which the room is located: room 540 will typically be found adjacent to room 542, and room 532 adjacent to room 530. In a four digit room number, this digit will be the third digit instead of the second.

The third digit is then assigned based on the side of the hall

Hall

In architecture, a hall is fundamentally a relatively large space enclosed by a roof and walls. In the Iron Age, a mead hall was such a simple building and was the residence of a lord and his retainers...

 on which the room is located: usually, one side of the hall has odd-numbered

Even and odd numbers

In mathematics, the parity of an object states whether it is even or odd.This concept begins with integers. An even number is an integer that is "evenly divisible" by 2, i.e., divisible by 2 without remainder; an odd number is an integer that is not evenly divisible by 2...

rooms and the opposite side has even-numbered rooms. In a four digit room numbers, this digit will be represented by the fourth digit instead of the third. Where a room is subdivided, the subdivisions are generally denoted by appending a letter suffix to the room number: for example, room 412 may be subdivided into rooms 412A and 412B.

A letter may appear before the numbers to indicate a particular building or wing. For example, Room D149 is a room in D building.

An offset may be used to accommodate unnumbered floors. For example, in a building with floors labeled G, M, 1, 2, ..., 11 and 12, the 4th room in each of those floors could be numbered 104, 114, 124, 134, ..., 224, and 234, respectively — with an offset of 11 in the floor numbers. This trick is sometimes used to make the floor number slightly less obvious, e.g. for security or marketing reasons.

Apartment Numbers

Some apartments are numbered using the regular room number assignment method, where apartment 1412 will be the 12th room on the fourteenth floor. Some apartments, however, are assigned with a number followed by a letter. There may be one or two numbers in the apartment number, followed by just one letter. For example, apartment 14R would be on the fourteenth floor. Apartment 7B would be on the seventh floor. Some apartment buildings may use compass points or the letters F, C, or R to indicate the front, center, or rear apartment on a given floor, or a combination of the two. For example, apartment 4RS would be on the 4th floor, and is the south apartment in the rear of the building.