Seven-segment display

It has been suggested that this article be merged with Eight-segment display, Nine-segment display, Fourteen-segment display and Sixteen-segment display to Segment display. (Discuss) Proposed since March 2026.

A seven-segment display is a display device for digits and some letters. It is often used in a device to display numbers – for example in a digital clock or calculator. To a lesser extent, but still common, it is used to display alphanumeric information. Since a seven-segment display tends to be less expensive than a display that can better represent any character and even a graphic image such as a dot matrix display, the design choice to use a seven-segment display is a tradeoff to minimize cost over providing richer functionality.^[1]

Seven-segment representation of figures can be found in patents as early as 1903 (in U.S. patent 1,126,641), when Carl Kinsley invented a method of telegraphically transmitting letters and numbers and having them printed on tape in a segmented format. In 1908, F. W. Wood invented an 8-segment display, which displayed the number 4 using a diagonal bar (U.S. patent 974,943). In 1910, a seven-segment display illuminated by incandescent bulbs was used on a power-plant boiler room signal panel.^[2] They were also used to show the dialed telephone number to operators during the transition from manual to automatic telephone dialing.^[3] They did not achieve widespread use until the advent of LEDs in the 1970s.

Some early seven-segment displays used incandescent filaments in an evacuated bulb; they are also known as numitrons.^[4] A variation (minitrons) made use of an evacuated potted box. Minitrons are filament segment displays that are housed in DIP (dual in-line package) packages like modern LED segment displays. They may have up to 16 segments.^[5][6][7] There were also segment displays that used small incandescent light bulbs instead of LEDs or incandescent filaments. These worked similarly to modern LED segment displays.^[8]

Vacuum fluorescent display versions were also used in the 1970s.^[9]

Many early (c. 1970s) LED seven-segment displays had each digit built on a single die. This made the digits very small. Some included magnifying lenses in the design to try to make the digits more legible.^[10][11] Other designs used 1 or 2 dies for every segment of the display.^[12][13]

Liquid-crystal display (LCD) largely superseded LED seven-segment displays. The shapes of elements in an LCD panel are arbitrary since they are formed on the display by photolithography, while LED segments tend to be simple rectangles, because they have to be physically moulded to shape, which makes it difficult to form more complex shapes. However, the easy recognition of seven-segment displays, and the comparatively high visual contrast obtained by such displays relative to dot-matrix digits, makes seven-segment multiple-digit LCD screens very common on basic calculators.

Seven-segment displays have been recommended against for critical information (i.e. information that is dangerous to health or safety if misread) due to misreading if upside down or if segments are "stuck" on or off.^[14] Backlit dot-matrix LCDs have largely superseded seven-segment displays on such equipment.

The seven-segment display has inspired type designers to produce typefaces reminiscent of that display (but more legible), such as New Alphabet, "DB LCD Temp", "ION B", etc. The seven-segment pattern is sometimes used in posters or tags, where the user either applies color to pre-printed segments, or applies color through a seven-segment digit template, to compose figures such as product prices or telephone numbers.

Seven-segment displays, which use a restricted range of letters that look like (upside-down) digits, are commonly used by school children to form words and phrases using a technique known as "calculator spelling."

Seven-segment displays may use a liquid-crystal display (LCD), a light-emitting diode (LED) for each segment, an electrochromic display, or other light-generating or -controlling techniques such as cold cathode gas discharge (neon) (Panaplex), vacuum fluorescent (VFD), incandescent filaments (Numitron), and others. For gasoline price totems and other large signs, electromechanical seven-segment displays made up of electromagnetically flipped light-reflecting segments are still commonly used. A precursor to the 7-segment display in the 1950s through the 1970s was the cold-cathode, neon-lamp-like nixie tube. Starting in 1970, RCA sold a display device known as the Numitron that used incandescent filaments arranged into a seven-segment display.^[15] In USSR, the first electronic calculator "Vega", which was produced from 1964, contains 20 decimal digits with seven-segment electroluminescent display.^[16]

In a simple LED package, typically all of the cathodes (negative terminals) or all of the anodes (positive terminals) of the segment LEDs are connected and brought out to a common pin; this is referred to as a "common cathode" or "common anode" device.^[17] Hence a 7 segment plus decimal point package will only require nine pins, though commercial products typically contain more pins, and/or spaces where pins would go, in order to match standard IC sockets. Integrated displays also exist, with single or multiple digits. Some of these integrated displays incorporate their own internal decoder, though most do not: each individual LED is brought out to a connecting pin as described.

Multiple-digit LED displays as used in pocket calculators and similar devices used multiplexed displays to reduce the number of I/O pins required to control the display. For example, all the anodes of the A segments of each digit position would be connected together and to a driver circuit pin, while the cathodes of all segments for each digit would be connected. To operate any particular segment of any digit, the controlling integrated circuit would turn on the cathode driver for the selected digit, and the anode drivers for the desired segments; then after a short blanking interval the next digit would be selected and new segments lit, in a sequential fashion. In this manner an eight digit display with seven segments and a decimal point would require only 8 cathode drivers and 8 anode drivers, instead of sixty-four drivers and IC pins.^[18] Often in pocket calculators the digit drive lines would be used to scan the keyboard as well, providing further savings; however, pressing multiple keys at once would produce odd results on the multiplexed display.

The seven segments are arranged as a rectangle, with two vertical segments on each side and one horizontal segment each at the top, middle, and bottom. Often the rectangle is oblique (slanted), which may aid readability. In most applications, the segments are of nearly uniform shape and size (usually elongated hexagons, though trapezoids and rectangles can also be used); though in the case of adding machines, the vertical segments are longer and more oddly shaped at the ends, to try to make them more easily readable. The seven elements of the display can be lit in different combinations to represent each of the Arabic numerals.

The individual segments are referred to by the letters "a" to "g", and an optional decimal point (an "eighth segment", referred to as DP) is sometimes used for the display of non-integer numbers.^[19][17] A single byte can encode the full state of a seven-segment display, including the decimal point. The most popular bit encodings are gfedcba and abcdefg. In the gfedcba representation, a byte value of 0x06 would turn on segments "c" and "b", which would display a "1" ().

The numerical digits 0 to 9 are the most common characters displayed on seven-segment displays. The most common patterns used for each of these are:^[21]

Alternative patterns: The numeral 1 may be represented with the left segments, the numerals 6 and 9 may be represented without a "tail", and the numeral 7 represented with a "tail":^[22]

In Unicode 13.0, 10 codepoints had been given for segmented digits 0–9 in the Symbols for Legacy Computing block, to replicate early computer fonts that included seven-segment versions of the digits.^[23] The official reference shows the less-common four-segment "7" ().

The binary-coded decimal (BCD) 0 to 9 digit values require four binary bits to hold their values. Since four bits (2⁴) can hold 16 values, this means hexadecimal (hex) digits can be represented by four bits too.^[24] Due to the limited number of segments in seven-segment displays, the hexadecimal digits B and D are displayed as lowercase letters to avoid confusion with 8 () and 0 () respectively.^{[25][26][27][28]} The digit "6" must also be displayed with the topmost segment as to avoid ambiguity with the letter "b" ().

Early decoder ICs often produced unintuitive patterns or duplicates of digits for 10-15,^[29] as they were designed to use as few gates as possible and only required to produce 0-9.

Many letters of the Latin alphabet can be reasonably implemented on a seven-segment display. Though not every letter is available, it is possible to create many useful words. By careful choice of words, one can sometimes work around unavailable letters. Uppercase letters "B", "I", "S", "Z", and "D" & "O" conflict with the common seven-segment representation of digits "8", "1", "5", "2", and "0" (, , , , ) respectively, and the lowercase letter "g" with digit "9" (). Upper case I () could be put on the left (as lower-case L is shown here) but this is not often done. Lowercase 'b' and 'q' are identical to the alternate numerical digits '6' and '9' (, ).

Latin alphabet

	A	B	C	D	E	F	G	H	I	J	K	L	M	N	O	P	Q	R	S	T	U	V	W	X	Y	Z
Upper
Lower

The following are some English word examples seen on actual electronic equipment (first line appeared on some CD players):

, , , , ,

, , , , , ,

, , , , , ,

There are also fourteen- and sixteen-segment displays (for full alphanumerics); however, these have mostly been replaced by dot matrix displays. 22-segment displays capable of displaying the full ASCII character set^[30] were briefly available in the early 1980s but did not prove popular.

• Eight-segment display
• Nine-segment display
• Fourteen-segment display
• Sixteen-segment display
• Dot matrix display
• Nixie tube display
• Vacuum fluorescent display

Wikimedia Commons has media related to Seven segment display.

• Interactive Demonstration of a Seven Segment Display
• Interfacing Seven Segment Display to 8051 Microcontroller
• Interfacing 7-Segment Display with AVR Microcontroller