A seven-segment display is a

display device A display device is an output device for presentation of information in visual or tactile form (the latter used for example in tactile electronic displays for blind people). When the input information that is supplied has an electrical signa ...

for

Arabic numerals The ten Arabic numerals (0, 1, 2, 3, 4, 5, 6, 7, 8, and 9) are the most commonly used symbols for writing numbers. The term often also implies a positional notation number with a decimal base, in particular when contrasted with Roman numera ...

, less complex than a device that can show more characters such as dot matrix displays. Seven-segment displays are widely used in digital clocks, electronic meters, basic calculators, and other electronic devices that display numerical information.

History

Seven-segment representation of figures can be found in

patent A patent is a type of intellectual property that gives its owner the legal right to exclude others from making, using, or selling an invention for a limited period of time in exchange for publishing an sufficiency of disclosure, enabling discl ...

s as early as 1903 (in ), 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 (). In 1910, a seven-segment display illuminated by incandescent bulbs was used on a power-plant boiler room signal panel. They were also used to show the dialed telephone number to operators during the transition from manual to automatic telephone dialing. They did not achieve widespread use until the advent of

LED A light-emitting diode (LED) is a semiconductor device that emits light when current flows through it. Electrons in the semiconductor recombine with electron holes, releasing energy in the form of photons. The color of the light (corresp ...

s in the 1970s. Some early seven-segment displays used incandescent filaments in an evacuated bulb; they are also known as numitrons. A variation (minitrons) made use of an evacuated potted box. Minitrons are filament segment displays that are housed in DIP (

dual in-line package In microelectronics, a dual in-line package (DIP or DIL) is an Semiconductor package, electronic component package with a rectangular housing and two parallel rows of electrical connecting pins. The package may be through-hole technology, throu ...

) packages like modern LED segment displays. They may have up to 16 segments. 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.

Vacuum fluorescent display A vacuum fluorescent display (VFD) is a display device once commonly used on consumer electronics equipment such as video cassette recorders, car audio, car radios, and microwave ovens. A VFD operates on the principle of cathodoluminescence, ...

versions were also used in the 1970s. 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. Other designs used 1 or 2 dies for every segment of the display. 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. For many applications, dot-matrix

liquid-crystal display A liquid-crystal display (LCD) is a flat-panel display or other Electro-optic modulator, electronically modulated optical device that uses the light-modulating properties of liquid crystals combined with polarizers to display information. Liq ...

s (LCDs) have largely superseded LED displays in general, though even in LCDs, seven-segment displays are common. Unlike LEDs, the shapes of elements in an LCD panel are arbitrary since they are formed on the display by

photolithography Photolithography (also known as optical lithography) is a process used in the manufacturing of integrated circuits. It involves using light to transfer a pattern onto a substrate, typically a silicon wafer. The process begins with a photosensiti ...

. In contrast, the shapes of LED segments tend to be simple

rectangle In Euclidean geometry, Euclidean plane geometry, a rectangle is a Rectilinear polygon, rectilinear convex polygon or a quadrilateral with four right angles. It can also be defined as: an equiangular quadrilateral, since equiangular means that a ...

s, because they have to be physically moulded to shape, which makes it difficult to form more complex shapes than the segments of seven-segment displays. 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

calculator An electronic calculator is typically a portable electronic device used to perform calculations, ranging from basic arithmetic to complex mathematics. The first solid-state electronic calculator was created in the early 1960s. Pocket-si ...

s. The seven-segment display has inspired

type design Type design is the art and process of designing typefaces. This involves drawing each letterform using a consistent style. The basic concepts and design variables are described below. A typeface differs from other modes of graphic production su ...

ers to produce typefaces reminiscent of that display (but more legible), such as New Alphabet, "DB LCD Temp", "ION B", etc. Using a restricted range of letters that look like (upside-down) digits, seven-segment displays are commonly used by school children to form words and phrases using a technique known as "

calculator spelling Calculator spelling is an Unintended consequences, unintended characteristic of the seven-segment display traditionally used by calculators, in which, when read upside-down, the digits resemble letters of the Latin alphabet. Each digit may be mapp ...

". Fuel_prices.jpg,

Gas station A filling station (also known as a gas station [] or petrol station []) is a facility that sells fuel and engine lubricants for motor vehicles. The most common fuels sold are gasoline (or petrol) and diesel fuel. Fuel dispensers are used to ...

price display SHARP ELSIMATE EL-W221.jpg,

Calculator An electronic calculator is typically a portable electronic device used to perform calculations, ranging from basic arithmetic to complex mathematics. The first solid-state electronic calculator was created in the early 1960s. Pocket-si ...

that has a tail on the "7" digit Apollo Guidance Computer-Cité de l'Espace-IMG 1897.jpg,

Apollo Guidance Computer The Apollo Guidance Computer (AGC) was a digital computer produced for the Apollo program that was installed on board each Apollo command module (CM) and Apollo Lunar Module (LM). The AGC provided computation and electronic interfaces for guidanc ...

control panel reproduction Marantz CD63SE - fluorescent display in test mode.jpg, Marantax CD63SE

CD player A CD player is an electronic device that plays audio compact discs, which are a digital audio, digital optical disc data storage format. CD players were first sold to consumers in 1982. CDs typically contain recordings of audio material such a ...

with a

vacuum fluorescent display A vacuum fluorescent display (VFD) is a display device once commonly used on consumer electronics equipment such as video cassette recorders, car audio, car radios, and microwave ovens. A VFD operates on the principle of cathodoluminescence, ...

in test mode CD-changer_Marantz_CC-45_01.JPG, Marantz CC-45

display

Implementations

Seven-segment displays may use a

(LCD), a

light-emitting diode A light-emitting diode (LED) is a semiconductor device that emits light when current flows through it. Electrons in the semiconductor recombine with electron holes, releasing energy in the form of photons. The color of the light (corre ...

(LED) for each segment, an electrochromic display, or other light-generating or -controlling techniques such as

cold cathode A cold cathode is a cathode that is not electrically heated by a Electrical filament, filament.A negatively charged electrode emits electrons or is the positively charged terminal. For more, see field emission. A cathode may be considered "cold" ...

gas discharge (neon)
Panaplex
, vacuum fluorescent (VFD), incandescent filaments (Numitron), and others. For

gasoline Gasoline ( North American English) or petrol ( Commonwealth English) is a petrochemical product characterized as a transparent, yellowish, and flammable liquid normally used as a fuel for spark-ignited internal combustion engines. When for ...

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 A Nixie tube ( ), or cold cathode display, is an electronics, electronic device used for display device, displaying numerals or other information using glow discharge. The glass tube contains a wire-mesh anode and multiple cathodes, shaped like ...

. Starting in 1970,

RCA RCA Corporation was a major American electronics company, which was founded in 1919 as the Radio Corporation of America. It was initially a patent pool, patent trust owned by General Electric (GE), Westinghouse Electric Corporation, Westinghou ...

sold a display device known as the ' that used incandescent filaments arranged into a seven-segment display. In USSR, the first electronic calculator "Vega", which was produced from 1964, contains 20 decimal digits with seven-segment

electroluminescent display Electroluminescent displays (ELDs) are a type of flat panel display created by sandwiching a layer of electroluminescent material such as gallium arsenide between two layers of conductors. When current flows, the layer of material emits radiatio ...

. In a simple LED package, typically all of the

cathode A cathode is the electrode from which a conventional current leaves a polarized electrical device such as a lead-acid battery. This definition can be recalled by using the mnemonic ''CCD'' for ''Cathode Current Departs''. Conventional curren ...

s (negative terminals) or all of the

anode An anode usually is an electrode of a polarized electrical device through which conventional current enters the device. This contrasts with a cathode, which is usually an electrode of the device through which conventional current leaves the devic ...

s (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. 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 In electronics, a driver is a electrical circuit, circuit or electronic component, component used to control another circuit or component, such as a high-power transistor, liquid crystal display (LCD), stepper motors, Static random-access memor ...

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. 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. Although to a naked eye all digits of an LED display appear lit, only one digit is lit at any given time in a multiplexed display. The digit changes at a high enough rate that the human eye cannot see the flashing (on earlier devices it could be visible to peripheral vision). LED Digital Display.jpg, A

multiplexed In telecommunications and computer networking, multiplexing (sometimes contracted to muxing) is a method by which multiple analog or digital signals are combined into one signal over a shared medium. The aim is to share a scarce resource— ...

4-digit, seven-segment display with only 12 pins 7segment multiplexing.gif, A 4-digit display scanning by columns to make the number 1.234 8-digit-multiplex-7-segment-LED-X-Ray.tif, X-Ray of an 8-digit 7-segment multiplexed LED display from a 1970s calculator

Characters

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

hexagon In geometry, a hexagon (from Greek , , meaning "six", and , , meaning "corner, angle") is a six-sided polygon. The total of the internal angles of any simple (non-self-intersecting) hexagon is 720°. Regular hexagon A regular hexagon is de ...

s, though

trapezoid In geometry, a trapezoid () in North American English, or trapezium () in British English, is a quadrilateral that has at least one pair of parallel sides. The parallel sides are called the ''bases'' of the trapezoid. The other two sides are ...

s and

s can also be used); though in the case of

adding machine An adding machine is a class of mechanical calculator, usually specialized for bookkeeping calculations. Consequently, the earliest adding machines were often designed to read in particular currencies. Adding machines were ubiquitous office ...

s, 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

. The individual segments are referred to by the letters "a" to "g", and an optional

decimal point FIle:Decimal separators.svg, alt=Four types of separating decimals: a) 1,234.56. b) 1.234,56. c) 1'234,56. d) ١٬٢٣٤٫٥٦., Both a comma and a full stop (or period) are generally accepted decimal separators for international use. The apost ...

(an "eighth segment", referred to as DP) is sometimes used for the display of non-integer numbers. 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". 7-segment

Decimal

The

numerical digit A numerical digit (often shortened to just digit) or numeral is a single symbol used alone (such as "1"), or in combinations (such as "15"), to represent numbers in positional notation, such as the common base 10. The name "digit" origin ...

s 0 to 9 are the most common characters displayed on seven-segment displays. The most common patterns used for each of these are: : 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':For example the fx-50F calculator from

Casio is a Japanese multinational electronics manufacturing corporation headquartered in Shibuya, Tokyo, Japan. Its products include calculators, mobile phones, digital cameras, electronic musical instruments, and analogue and digital watches. It ...

and other models from the same manufacturer. : In Unicode 13.0, 10 codepoints had been given for segmented digits 0–9 in the

Symbols for Legacy Computing Symbols for Legacy Computing is a Unicode block containing graphic characters that were used for various home computers from the 1970s and 1980s and in teletext broadcasting standards. It includes characters from the Amstrad CPC, MSX, Mattel Aqua ...

block, to replicate early computer fonts that included seven-segment versions of the digits. The official reference shows the less-common four-segment "7".

Hexadecimal

The

binary-coded decimal In computing and electronic systems, binary-coded decimal (BCD) is a class of binary encodings of decimal numbers where each digit is represented by a fixed number of bits, usually four or eight. Sometimes, special bit patterns are used f ...

(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 Hexadecimal (also known as base-16 or simply hex) is a Numeral system#Positional systems in detail, positional numeral system that represents numbers using a radix (base) of sixteen. Unlike the decimal system representing numbers using ten symbo ...

(hex) digits can be represented by four bits too. Since there are a limited number of segments in seven-segment displays, a couple of the hexadecimal digits are required to be displayed as lowercase letters, otherwise the uppercase letter "B" would be the same as the digit "8", and the uppercase letter "D" would be the same as the digit "0". The digit "6" must also be displayed with the topmost segment as to avoid ambiguity with the letter "b". : Early decoder IC's often produced random patterns or duplicates of digits for 10-15, as they were designed to use as few gates as possible and only required to produce 0-9.

Letters

Many letters of the

Latin alphabet The Latin alphabet, also known as the Roman alphabet, is the collection of letters originally used by the Ancient Rome, ancient Romans to write the Latin language. Largely unaltered except several letters splitting—i.e. from , and from � ...

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 "I", "O", "S", "Z" conflict with the common seven-segment representation of digits "1", "0", 5", "2", and the lowercase letter "g" with digit "9". Upper case 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'. : The following are some real world English word examples seen on actual electronic equipment (first line appeared on some

s): :, , , , , :, , , , , , :, , , , , ,

References

External links

Interactive Demonstration of a Seven Segment Display

Interfacing 7-Segment Display with AVR Microcontroller
{{Display technology Display technology