- Seven-segment display character representations
The topic of seven-segment display character representations revolves around the various shapes of
numerical digits, letters, and punctuationdevisable on seven-segment displays. Such representation of characters is not standardized by any relevant entity (e.g. ISO, IEEEor IEC).
Two basic conventions can be seen for
Arabic numerals: one lights the additional segment in 6 (segment A), 7 (F) and 9 (D); the other, more anglophoneone does not. Military, mission critical, and safety-of-life applications prefer the latter. The idea is to use a display font where a single burned out or missing segment in a digit will not display as a different valid digit.
In addition to the ten digits, seven-segment displays can be used to show letters of the latin, cyrillic and
greek alphabets including punctuation, but only few representations are unambiguous and intuitive at the same time: uppercase "A", "B", "C", "E", "F", "G", "H", "I", "J", "L", "N", "O", "P", "S", "U", "Y", "Z", and lowercase "a", "b", "c", "d", "e", "g", "h", "i", "n", "ñ", "o", "q", "r", "t", "u".Also, alphabetic letters, and many other characters, are much clearer, and unambiguously shown on the currently ubiquitous and low-priced dot matrix displays, as well as on fourteen-segment and sixteen-segment displays. All this obviates the need for seven-segment displays to show letters in all but the most special cases.
One such special case is the display of the letters A–F when denoting the
hexadecimalvalues (digits) 10–15. These are needed on some scientific calculators, and are used with some test displays on electronic equipment. Although there is no official standard, most devices displaying hex digits use the unique forms shown in the leftmost column of the Latin alphabet section below — uppercase A, C, E, and F, and lowercase b and d.
All in all,
ad hocand corporate solutions dominate the field of using seven-segment displays to show general words and phrases. Such applications of seven-segment displays are usually not considered essential and are only used for basic notifications on consumer electronics appliances (as is the case of this article's Example phrases), and as internal test messages on equipment under development.
Display pattern tables
The tables below show alternative seven-segment display patterns for the
Arabic numerals, the 26 letters of the English language part of the Latin alphabet, and the Greek alphabet. Finally, some examples of words spelled using the patterns are shown.
The following phrases come from a
portable media player's seven-segment display. They give a good illustration of an application where a 7-segment display may be sufficient for displaying letters, since the relevant messages are neither life/mission critical, nor in any significant risk of being misunderstood, much due to the limited number and rigid domain specificity of the messages. As such, there is no direct need for a more expressive display in this case, although even a slightly wider repertoire of messages would require at least a 14- or 16-segment display, if not a dot matrix one.
* [http://www.twyman.org.uk/Fonts/ Harvey Twyman's seven-segment TrueType fonts]
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