flag (plural flags)
1. A piece of cloth, often decorated with an emblem, used as a visual signal or symbol.
2. (Nautical) A flag flown by a ship to show the presence on board of the admiral; the admiral himself, or his flagship
3. The use of a flag, especially to indicate the start of a race or other event
4. (Computer Science) A variable or memory location that stores a true-or-false, yes-or-no value, typically either recording the fact that a certain event has occurred or requesting that a certain optional action take place.
5. (Computer Science) In a command line interface, a notation requesting optional behavior or otherwise modifying the action of the command being invoked.
A flag is a piece of cloth, often flown from a pole or mast, generally used symbolically for signalling or identification. The term flag is also used to refer to the graphic design employed by a flag, or to its depiction in another media.
The first flags were used to assist military coordination on battlefields and flags have evolved into a general tool for rudimentary signalling and identification, especially in environments where communication is similarly challenging (such as the maritime environment where semaphore is used). National flags are potent patriotic symbols with varied wide-ranging interpretations, often including strong military associations due to their original and ongoing military uses. Flags are used in messaging, advertising, or for other decorative purposes, though at this less formal end the distinction between a flag and a simple cloth banner is blurred. The study of flags is known as vexillology, from the Latin vexillum meaning flag or banner.
Although flag-like symbols were used in some ancient cultures, the origin of flags in the modern sense is a matter of dispute. Some believe flags originated in China, while others hold that the Roman Empire's vexillum was the first true flag. Originally, the standards of the Roman legions were not flags, but symbols like the eagle of Augustus Caesar's Xth legion; this eagle would be placed on a staff for the standard-bearer to hold up during battle. But a military unit from Scythia had for a standard a dragon with a flexible tail which would move in the wind; the legions copied this; eventually all the legions had flexible standards — our modern-day flag.
During the Middle Ages, flags were used mainly during battles to identify individual leaders: in Europe the knights, in Japan the samurai, and in China the generals under the imperial army.
From the time of Christopher Columbus onwards, it has been customary (and later a legal requirement) for ships to carry flags designating their nationality; these flags eventually evolved into the national flags and maritime flags of today. Flags also became the preferred means of communications at sea, resulting in various systems of flag signals; see International maritime signal flags.
As European knights were replaced by centralized armies, flags became the means to identify not just nationalities but also individual military units. Flags became much more elaborate, and were seen as objects to be captured or defended. Eventually these flags posed too much danger to those carrying them, and by World War I these were withdrawn from the battlefields, and have since been used only at ceremonial occasions.
A national flag is a flag that symbolises a country and that can usually be flown by citizens of that country. Both public and private buildings such as schools and courthouses often fly the national flag. In some countries, the national flags are only flown from non-military buildings on certain flag days. There are three distinct types of national flag for use on land, and three for use at sea, although many countries use identical designs for several (and sometimes all) of these types of flag.
Français : Drapeau
Norsk (bokmål): Flagg
Walon : Drapea