A graphic character, in computer programming, is any symbol that is part of a pre-defined character set but is not a letter or number. A character set is a sequence of symbols that a computer uses to display data. Character sets consist of letters, numbers, punctuation, control characters and graphical symbols. A single element of this set is a graphic character. There are many pre-defined character sets, each containing a variety of graphical characters or none at all.
A complete character set is a list of symbols, letters, numbers and punctuation that the computer can index by number to correctly display data. One example is a font, which is a character set. While each font on a computer might appear differently, the letters are all in the same order within the set. This means that, no matter what font is selected, the index of the letter "A" will always be the same.
Graphic characters exist within a character set. They are all of the characters that are not numbers or letters but are instead known as glyphs. These glyphs can be representational of different signs and symbols in different industries, or they might just be a collection of trivial shapes. This is because, while the alphanumeric portion of a character set is strictly defined by international standards, the graphical portion is not.
Originally, the American Standard Code for Information Interchange (ASCII) was the standard character set for most computers. The ASCII character set defined all characters above index 127 as a graphic character. ASCII was based on an eight-bit system, so there were 256 characters, maximum, available in the set. This meant there were 128 spaces for graphic characters, all of which were filled.
The earliest common use for a graphic character was to draw windows and other shapes on the screen while in text mode. The advent of fully graphical operating systems removed this need, however, and these characters became sparsely used, mainly in console applications. As time progressed, different countries established their own character sets, most of which were incompatible with each other. Development of the Unicode® character set resolved this problem in later years.
The establishment of Unicode® as the international standard for character sets unified all of the disparate sets that existed. Unicode® allows for many more characters than ASCII did and also reserves space for glyphs and other graphic character representations, such as arrows. The use of a graphic character in 2011 is primarily done when it is necessary to show a mathematical or other technical symbol.
Within a character set, there are special characters, known as control characters, that do not visually appear on the screen but instead dictate an action to be taken by the computer. These include line feed, return and backspace. The character for a blank space is considered both a control character and a graphic character even though it does not technically have a visual representation. Space is the only graphic character that also is a control character.
