The slashed zero, , is a representation of the
Arabic digit
The ten Arabic numerals (0, 1, 2, 3, 4, 5, 6, 7, 8, and 9) are the most commonly used numerical digit, symbols for writing Number, numbers. The term often also implies a positional notation number with a decimal base, in particular when contra ...
zero
0 (zero) is a number representing an empty quantity. Adding (or subtracting) 0 to any number leaves that number unchanged; in mathematical terminology, 0 is the additive identity of the integers, rational numbers, real numbers, and compl ...
("0") with a
slash
Slash may refer to:
* Slash (punctuation), the "/" character
Arts and entertainment Fictional characters
* Slash (Marvel Comics)
* Slash (''Teenage Mutant Ninja Turtles'')
Music
* Harry Slash & The Slashtones, an American rock band
* Nash th ...
through it. This variant zero glyph is often used to distinguish the digit zero from the
Latin script
The Latin script, also known as the Roman script, is a writing system based on the letters of the classical Latin alphabet, derived from a form of the Greek alphabet which was in use in the ancient Greek city of Cumae in Magna Graecia. The Gree ...
letter
O anywhere that the distinction needs emphasis, particularly in
encoding
In communications and Data processing, information processing, code is a system of rules to convert information—such as a letter (alphabet), letter, word, sound, image, or gesture—into another form, sometimes data compression, shortened or ...
systems, scientific and engineering applications,
computer programming
Computer programming or coding is the composition of sequences of instructions, called computer program, programs, that computers can follow to perform tasks. It involves designing and implementing algorithms, step-by-step specifications of proc ...
(such as
software development
Software development is the process of designing and Implementation, implementing a software solution to Computer user satisfaction, satisfy a User (computing), user. The process is more encompassing than Computer programming, programming, wri ...
), and telecommunications. It thus helps to differentiate characters that would otherwise be
homoglyph
In orthography and typography, a homoglyph is one of two or more graphemes, character (computing), characters, or glyphs with shapes that appear identical or very similar but may have differing meaning. The designation is also applied to sequence ...
s. It was commonly used during the
punch card
A punched card (also punch card or punched-card) is a stiff paper-based medium used to store digital information via the presence or absence of holes in predefined positions. Developed over the 18th to 20th centuries, punched cards were wide ...
era, when programs were typically written out by hand, to avoid ambiguity when the character was later typed on a
card punch
A computer punched card reader or just computer card reader is a computer input device used to read Computer program, computer programs in either source or executable form and Data (computing), data from punched cards. A computer card punch is a ...
.
Usage

The slashed zero is used in a number of fields in order to avoid confusion with the letter "O". It is used by
computer programmer
A programmer, computer programmer or coder is an author of computer source code someone with skill in computer programming.
The professional titles ''software developer'' and ''software engineer'' are used for jobs that require a progr ...
s, in recording
amateur radio
Amateur radio, also known as ham radio, is the use of the radio frequency radio spectrum, spectrum for purposes of non-commercial exchange of messages, wireless experimentation, self-training, private recreation, radiosport, contesting, and emer ...
call signs and in military radio, as logs of such contacts tend to contain both letters and numerals.
The slashed zero was used on teleprinter circuits for weather applications. In this usage it was sometimes called communications zero.
The slashed zero can be used in
stoichiometry
Stoichiometry () is the relationships between the masses of reactants and Product (chemistry), products before, during, and following chemical reactions.
Stoichiometry is based on the law of conservation of mass; the total mass of reactants must ...
to avoid confusion with the symbol for
oxygen
Oxygen is a chemical element; it has chemical symbol, symbol O and atomic number 8. It is a member of the chalcogen group (periodic table), group in the periodic table, a highly reactivity (chemistry), reactive nonmetal (chemistry), non ...
(capital O).
The slashed zero is also used in charting and documenting in the medical and healthcare fields to avoid confusion with the letter "O". It also denotes an absence of something (similar to the usage of an "
empty set
In mathematics, the empty set or void set is the unique Set (mathematics), set having no Element (mathematics), elements; its size or cardinality (count of elements in a set) is 0, zero. Some axiomatic set theories ensure that the empty set exi ...
" character), such as a sign or a symptom.
Slashed zeros are used on
New Zealand number plates.
History
The slashed zero predates computers, and is known to have been used in the twelfth and thirteenth centuries.
In the days of the
typewriter
A typewriter is a Machine, mechanical or electromechanical machine for typing characters. Typically, a typewriter has an array of Button (control), keys, and each one causes a different single character to be produced on paper by striking an i ...
, there was no key for the slashed zero. Typists could generate it by first typing either an uppercase "O" or a zero and then
backspace
Backspace (, ⌫) is the keyboard key that in typewriters originally pushed the carriage one position backwards, and in modern computer systems typically moves the display cursor one position backwards,The meaning of "backwards" depends on the dir ...
, followed by typing the slash key. The result would look very much like a slashed zero.
It is used in many
Baudot teleprinter
A teleprinter (teletypewriter, teletype or TTY) is an electromechanical device that can be used to send and receive typed messages through various communications channels, in both point-to-point (telecommunications), point-to-point and point- ...
applications, specifically the keytop and typepallet that combines "P" and slashed zero.
[ Additionally, the slashed zero is used in many ]ASCII
ASCII ( ), an acronym for American Standard Code for Information Interchange, is a character encoding standard for representing a particular set of 95 (English language focused) printable character, printable and 33 control character, control c ...
graphic sets descended from the default typewheel on the Teletype Model 33
The Teletype Model 33 is an electromechanical teleprinter designed for light-duty office use. It is less rugged and cost less than earlier Teletype models. The Teletype Corporation introduced the Model 33 as a commercial product in 1963, after ...
.[
The use of the slashed zero by many computer systems of the 1970s and 1980s inspired the 1980s ]space rock
Space rock is a music genre characterized by loose and lengthy song structures centered on instrumental textures that typically produce a hypnotic, otherworldly sound. It may feature distorted and reverberation-laden guitars, minimal drummin ...
band Underground Zerø
Underground Zerø is a British space rock band, based in Norfolk, UK. The band is also known as UZØ. While the band is often referred to as "Underground Zero" or "Underground Zer0" in print, the official name of the band includes the slashed ze ...
to use a heavy metal umlaut
A metal umlaut (also known as röck döts) is a diacritic that is sometimes used gratuitously or decoratively over letters in the names of mainly hard rock or heavy metal bands—for example, those of Blue Öyster Cult, Queensrÿche, Motörhea ...
Scandinavian vowel
A vowel is a speech sound pronounced without any stricture in the vocal tract, forming the nucleus of a syllable. Vowels are one of the two principal classes of speech sounds, the other being the consonant. Vowels vary in quality, in loudness a ...
'' ø'' in the band's name and as the band logo on all their album covers.
Along with the Westminster
Westminster is the main settlement of the City of Westminster in Central London, Central London, England. It extends from the River Thames to Oxford Street and has many famous landmarks, including the Palace of Westminster, Buckingham Palace, ...
, MICR
Magnetic ink character recognition code, known in short as MICR code, is a character recognition technology used mainly by the banking industry to streamline the processing and clearance of cheques and other documents. MICR encoding, called the ...
, and OCR-A
OCR-A is a font issued in 1966 and first implemented in 1968. A special font was needed in the early days of computer optical character recognition, when there was a need for a font that could be recognized not only by the computers of that day, b ...
fonts, the slashed zero became one of the things associated with hacker culture
The hacker culture is a subculture of individuals who enjoy—often in collective effort—the intellectual challenge of creatively overcoming the limitations of software systems or electronic hardware (mostly digital electronics), ...
in the 1980s. Some cartoons depicted computer users talking in binary code
A binary code represents plain text, text, instruction set, computer processor instructions, or any other data using a two-symbol system. The two-symbol system used is often "0" and "1" from the binary number, binary number system. The binary cod ...
with 1s and 0s using a ''slashed zero'' for the 0.
Slashed zeroes have been used in the Flash-based artwork of Young-Hae Chang Heavy Industries, notably in their 2003 work, ''Operation Nukorea''. The reason for their use is unknown, but has been conjectured to be related to themes of "negation, erasure, and absence".[
]
Similar symbols
The ''slashed zero'' has the disadvantage that it can be confused with several other symbols. See the disambiguation page for the symbol Ø for a comprehensive listing.
Representation in Unicode and HTML
In Unicode
Unicode or ''The Unicode Standard'' or TUS is a character encoding standard maintained by the Unicode Consortium designed to support the use of text in all of the world's writing systems that can be digitized. Version 16.0 defines 154,998 Char ...
, slashed zero is considered a standardized typographic variation of the Arabic digit
The ten Arabic numerals (0, 1, 2, 3, 4, 5, 6, 7, 8, and 9) are the most commonly used numerical digit, symbols for writing Number, numbers. The term often also implies a positional notation number with a decimal base, in particular when contra ...
zero , which is code point . Appending Variation Selector 1 after the zero creates the "short diagonal stroked form", on this browser it produces .
Note that the above should not be confused with the "slashed zero variant of the empty set
In mathematics, the empty set or void set is the unique Set (mathematics), set having no Element (mathematics), elements; its size or cardinality (count of elements in a set) is 0, zero. Some axiomatic set theories ensure that the empty set exi ...
", , as popularized by Donald Knuth's TeX
Tex, TeX, TEX, may refer to:
People and fictional characters
* Tex (nickname), a list of people and fictional characters with the nickname
* Tex Earnhardt (1930–2020), U.S. businessman
* Joe Tex (1933–1982), stage name of American soul singer ...
. Unicode represents that character as the empty set (∅) with variation selector 1.
Prior to Unicode 9.0, there was no code point
A code point, codepoint or code position is a particular position in a Table (database), table, where the position has been assigned a meaning. The table may be one dimensional (a column), two dimensional (like cells in a spreadsheet), three dime ...
defined for altering the visual appearance of zero. This meant that the slashed zero glyph
A glyph ( ) is any kind of purposeful mark. In typography, a glyph is "the specific shape, design, or representation of a character". It is a particular graphical representation, in a particular typeface, of an element of written language. A ...
was displayed for only—''and then always''—in fonts whose designer chose the option. Successful display on a particular local system depended on making sure that such a font was available — either via the system's font files or via font embedding
Font embedding is the inclusion of font files inside an electronic document for display across different platforms. Font embedding is controversial because it allows licensed fonts to be freely distributed.
History
Font embedding has been possibl ...
— and selected. (See also, Combining solidus below.)
In HTML
Hypertext Markup Language (HTML) is the standard markup language for documents designed to be displayed in a web browser. It defines the content and structure of web content. It is often assisted by technologies such as Cascading Style Sheets ( ...
, slashed zero can be enabled by using CSS property font-variant-numeric: slashed-zero or alternatively font-feature-settings: 'zero'. If the font has support for OpenType
OpenType is a format for scalable computer fonts. Derived from TrueType, it retains TrueType's basic structure but adds many intricate data structures for describing typographic behavior. OpenType is a registered trademark of Microsoft Corpora ...
feature tag zero
, slashed zero will be substituted.
Typography
In most typographic designs, the slash of a slashed zero usually does not extend past the ellipse. Compare this to the Scandinavian vowel
A vowel is a speech sound pronounced without any stricture in the vocal tract, forming the nucleus of a syllable. Vowels are one of the two principal classes of speech sounds, the other being the consonant. Vowels vary in quality, in loudness a ...
" Ø", the "empty set
In mathematics, the empty set or void set is the unique Set (mathematics), set having no Element (mathematics), elements; its size or cardinality (count of elements in a set) is 0, zero. Some axiomatic set theories ensure that the empty set exi ...
" symbol "∅" and the diameter symbol ⌀
In geometry, a diameter of a circle is any straight line segment that passes through the centre of the circle and whose endpoints lie on the circle. It can also be defined as the longest chord of the circle. Both definitions are also valid for ...
.
A convention common on early line printer
Printer may refer to:
Technology
* Printer (publishing), a person
* Printer (computing), a hardware device
* Optical printer for motion picture films
People
* Nariman Printer (fl. c. 1940), Indian journalist and activist
* James Printer (1640 ...
s left zero unornamented but added a tail or hook to the letter-O so that it resembled an inverted Q (like U+213A ℺
A signature mark, in traditional bookbinding, is a letter, number or combination of either or both, which is printed at the bottom of the first page, or leaf, of a section.
The section is itself referred to as a signature, also called collatio ...
) or cursive
Cursive (also known as joined-up writing) is any style of penmanship in which characters are written joined in a flowing manner, generally for the purpose of making writing faster, in contrast to block letters. It varies in functionality and m ...
capital letter-O ().[
In the ]Fixedsys
''Fixedsys'' is a family of Bitmap font, raster monospaced fonts. The name means ''fixed system'', because its glyphs are monospace or fixed-width (although bolded characters are wider than non-bolded, unlike other monospace fonts such as Courier ...
typeface, the numeral 0 has two internal barbs along the lines of the slash. This appears much like a white "S" within the black borders of the zero.
In the FE-Schrift
The or ('forgery-impeding typeface') is a sans serif typeface introduced for use on license plate, licence plates. Its monospaced letters and numbers are slightly disproportionate to prevent easy modification and to improve machine readabil ...
typeface, used on German car license plates, the zero is rectangular and has an "insinuated" slash: a diagonal crack just beneath the top right curve.
Typefaces
Typeface
A typeface (or font family) is a design of Letter (alphabet), letters, Numerical digit, numbers and other symbols, to be used in printing or for electronic display. Most typefaces include variations in size (e.g., 24 point), weight (e.g., light, ...
s commonly found on personal computers
A personal computer, commonly referred to as PC or computer, is a computer designed for individual use. It is typically used for tasks such as Word processor, word processing, web browser, internet browsing, email, multimedia playback, and PC ...
that use the slashed zero include:
* Terminal in Microsoft
Microsoft Corporation is an American multinational corporation and technology company, technology conglomerate headquartered in Redmond, Washington. Founded in 1975, the company became influential in the History of personal computers#The ear ...
's Windows
Windows is a Product lining, product line of Proprietary software, proprietary graphical user interface, graphical operating systems developed and marketed by Microsoft. It is grouped into families and subfamilies that cater to particular sec ...
line.
* Consolas
Consolas is a monospaced typeface designed by Luc(as) de Groot. It is a part of the ClearType Font Collection, a suite of fonts that take advantage of Microsoft's ClearType font rendering technology. It has been included with Windows since Windo ...
in Microsoft
Microsoft Corporation is an American multinational corporation and technology company, technology conglomerate headquartered in Redmond, Washington. Founded in 1975, the company became influential in the History of personal computers#The ear ...
's Windows Vista
Windows Vista is a major release of the Windows NT operating system developed by Microsoft. It was the direct successor to Windows XP, released five years earlier, which was then the longest time span between successive releases of Microsoft W ...
, Windows 7
Windows 7 is a major release of the Windows NT operating system developed by Microsoft. It was Software release life cycle#Release to manufacturing (RTM), released to manufacturing on July 22, 2009, and became generally available on October 22, ...
, Microsoft Office 2007
Microsoft Office 2007 (codenamed Office 12) is an office suite for Windows, developed and published by Microsoft. It was officially revealed on March 9, 2006 and was the 12th version of Microsoft Office. It was released to manufacturing on Novemb ...
and Microsoft Visual Studio 2010
* Menlo in macOS
macOS, previously OS X and originally Mac OS X, is a Unix, Unix-based operating system developed and marketed by Apple Inc., Apple since 2001. It is the current operating system for Apple's Mac (computer), Mac computers. With ...
* Monaco
Monaco, officially the Principality of Monaco, is a Sovereign state, sovereign city-state and European microstates, microstate on the French Riviera a few kilometres west of the Regions of Italy, Italian region of Liguria, in Western Europe, ...
in macOS
macOS, previously OS X and originally Mac OS X, is a Unix, Unix-based operating system developed and marketed by Apple Inc., Apple since 2001. It is the current operating system for Apple's Mac (computer), Mac computers. With ...
* SF Mono in macOS
macOS, previously OS X and originally Mac OS X, is a Unix, Unix-based operating system developed and marketed by Apple Inc., Apple since 2001. It is the current operating system for Apple's Mac (computer), Mac computers. With ...
[
* The ]Fedora
A fedora () is a hat with a soft brim and indented crown.Kilgour, Ruth Edwards (1958). ''A Pageant of Hats Ancient and Modern''. R. M. McBride Company. It is typically creased lengthwise down the crown and "pinched" near the front on both sides ...
Linux distribution ships with a tweaked variant of the Liberation typeface which adds a slash to the zero; this is not present on most other Linux distributions.
* ProFont
ProFont is a monospace typeface, font available in many formats. It is intended to be used for programming in Integrated development environment, IDE environments and it is available in Bitmap font, bitmap and TrueType versions for various Platfor ...
* Roboto
Roboto () is a typeface family developed by Google. The first typeface was created as the system font for its Android (operating system), Android operating system, and released in 2011 for Android Ice Cream Sandwich, Android 4.0 "Ice Cream Sa ...
Mono
Dotted zero typefaces:
* The DejaVu family of typefaces has a "DejaVu Sans Mono" variant with a dotted zero.
*Andalé Mono
Andalé Mono (for technical reasons also Andale Mono) is a monospaced sans-serif typeface designed by Steve Matteson for terminal emulation and software development environments, originally for the Taligent project by Apple Inc. and IBM. Andalé M ...
has a dotted zero.
* IBM Plex Mono uses a dotted zero.
*Source Code Pro
Source Code Pro is a monospaced sans serif typeface created by Paul D. Hunt for Adobe Systems. It is the second open-source font family from Adobe, distributed under the SIL Open Font License.
Source Code Pro (2012)
Source Code Pro is a set ...
and its associated typefaces use a dotted zero.
*Cascadia Code
Cascadia Code is a purpose-built monospaced TrueType font for Windows Terminal. It includes programming ligatures and was designed to enhance the look and feel of Windows Terminal, terminal applications and text editors such as Visual Studio and ...
, the default font for Windows Terminal
Windows Terminal is a Tabbed, multi-tabbed terminal emulator developed by Microsoft for Windows 10 and later as a replacement for Windows Console. It can run any command-line app in a separate tab. It is preconfigured to run Windows Command Pro ...
, Visual Studio
Visual Studio is an integrated development environment (IDE) developed by Microsoft. It is used to develop computer programs including web site, websites, web apps, web services and mobile apps. Visual Studio uses Microsoft software development ...
, and Visual Studio Code
Visual Studio Code, commonly referred to as VS Code, is an integrated development environment developed by Microsoft for Windows, Linux, macOS and web browsers. Features include support for debugging, syntax highlighting, intelligent code comp ...
, uses a dotted zero.
Variations
Dotted zero
The zero with a dot in the center seems to have originated as an option on IBM 3270
The IBM 3270 is a family of Block-oriented terminal, block oriented display and printer computer terminals introduced by IBM in 1971
and normally used to communicate with IBM mainframes. The 3270 was the successor to the IBM 2260 display ter ...
display controllers. The dotted zero may appear similar to the Greek letter
The Greek alphabet has been used to write the Greek language since the late 9th or early 8th century BC. It was derived from the earlier Phoenician alphabet, and is the earliest known alphabetic script to systematically write vowels as wel ...
theta
Theta (, ) uppercase Θ or ; lowercase θ or ; ''thē̂ta'' ; Modern: ''thī́ta'' ) is the eighth letter of the Greek alphabet, derived from the Phoenician letter Teth 𐤈. In the system of Greek numerals, it has a value of 9.
Gree ...
(particularly capital theta, Θ), but the two have different glyphs
A glyph ( ) is any kind of purposeful mark. In typography, a glyph is "the specific shape, design, or representation of a character". It is a particular graphical representation, in a particular typeface, of an element of written language. A ...
. In raster fonts, the theta usually has a horizontal line connecting, or nearly touching, the sides of an O; while the dotted zero simply has a dot in the middle. However, on a low-definition display, such a form can be confused with a numeral 8. In some fonts the IPA letter for a bilabial click
The bilabial clicks are a family of click consonants that sound like a smack of the lips. They are found as phonemes only in the small Tuu language family (currently two languages, one down to its last speaker), in the ǂ’Amkoe language ...
(ʘ) looks similar to the dotted zero.
Alternatively, the dot can become a vertical trace, for example by adding a "combining short vertical line overlay" (U+20D3)
. It may be coded as 0⃓
giving 0⃓.
Dotted zero is used on vehicle registration plates of Slovakia
Vehicles registered in Slovakia were generally assigned to one of the districts ('' okres'') and from 1997 until 2022, the license plate coding () generally consisted of seven characters and takes the form XX-NNNLL, where XX was a two letter code ...
since 2023.
Official templates of Slovak license plates (in Slovak)
Slashed letter 'O'
IBM
International Business Machines Corporation (using the trademark IBM), nicknamed Big Blue, is an American Multinational corporation, multinational technology company headquartered in Armonk, New York, and present in over 175 countries. It is ...
(and a few other early mainframe makers) used a convention in which the letter O had a slash and the digit 0 did not.[ This is even more problematic for ]Danes
Danes (, ), or Danish people, are an ethnic group and nationality native to Denmark and a modern nation identified with the country of Denmark. This connection may be ancestral, legal, historical, or cultural.
History
Early history
Denmark ...
, Faroese, and Norwegians
Norwegians () are an ethnic group and nation native to Norway, where they form the vast majority of the population. They share a common culture and speak the Norwegian language. Norwegians are descended from the Norsemen, Norse of the Early ...
because it means two of their letters — the O and slashed O ( Ø) — are visually similar.
This was later flipped and most mainframe chain or band printers used the opposite convention (letter O printed as is, and digit zero printed with a slash). This was the de facto standard from 1970s to 1990s. However current use of network laser printers that use PC style fonts caused the demise of the slashed zero in most companies — only a few configured laser printers to use it.
Combining solidus
Before Unicode
Unicode or ''The Unicode Standard'' or TUS is a character encoding standard maintained by the Unicode Consortium designed to support the use of text in all of the world's writing systems that can be digitized. Version 16.0 defines 154,998 Char ...
standardized the slashed variation of zero (0︀) seen above, it did allow composite characters which were used historically to obtain a crude typographic approximation
A typographic approximation is a replacement of an element of the writing system (usually a glyph) with another glyph or glyphs. The replacement may be a nearly homographic character, a digraph, or a character string. An approximation is differe ...
where a slash is drawn upon a zero. It is treated literally as "a zero that is slashed", and it is coded as two characters: a standard zero followed by either "combining short solidus overlay" or "combining long solidus overlay" . However, besides confusing the meaning of the digit zero, it will make a mess if the zero is already slashed in the font. There is no way to specify an unslashed zero that can always be safely overprinted. Laying a slash over letter O also risks wrong appearance and confusion.
For example, placing the "long solidus", which may be written in HTML
Hypertext Markup Language (HTML) is the standard markup language for documents designed to be displayed in a web browser. It defines the content and structure of web content. It is often assisted by technologies such as Cascading Style Sheets ( ...
as , appears as . Using the "short solidus overlay" after a standard zero character is coded as and produces the following: .
Reversed slash
Some Burroughs/Unisys
Unisys Corporation is a global technology solutions company founded in 1986 and headquartered in Blue Bell, Pennsylvania. The company provides cloud, AI, digital workplace, logistics, and enterprise computing services.
History Founding
Unis ...
equipment displays a zero with a ''reversed'' slash, similar to the no symbol
The general prohibition sign, also known informally as the no symbol, 'do not' sign, circle-backslash symbol, nay, interdictory circle, prohibited symbol, is a red circle with a 45-degree diagonal, diagonal line inside the circle from upper-lef ...
, , as does the free typeface Atkinson Hyperlegible
Atkinson Hyperlegible is a freely available typeface built around a grotesque sans-serif core, intended to be optimally legible for readers who are partially visually impaired, with all characters maximally distinguishable from one another. It w ...
.
See also
*0 (number)
0 (zero) is a number representing an empty quantity. Adding (or subtracting) 0 to any number leaves that number unchanged; in mathematical terminology, 0 is the additive identity of the integers, rational numbers, real numbers, and complex ...
*
*Names for the number 0 in English
" Zero" is the usual name for the number 0 in English. In British English "nought" is also used and in American English "naught" is used occasionally for zero, but (as with British English) "naught" is more often used as an archaic word for nothi ...
* Arabic numeral variations#Slashed zero
* Regional handwriting variation#Arabic numerals
References
Sources
*; .
External links
*{{citation , chapter-url= http://www.catb.org/~esr/jargon/html/0/numeral-zero.html , chapter= 0 , title= The Jargon File , publisher= Eric S Raymond.
Underground Zerø Album Cover
Underground Zerø Band Logo
Typographical symbols
Numeral systems
0 (number)