View source for Symbols for zero

{{Short description|Symbol representing the number or digit 0}}
The modern numerical digit [[0 (number)|0]] is usually written as a circle, an ellipse or a rounded square or rectangle.

==Glyphs==
[[File:Text figures 036.svg|71px|left]]

In most modern [[typeface]]s, the height of the 0 character is the same as the other digits. However, in typefaces with [[text figures]], the character is often shorter ([[x-height]]).

[[File:Zero o comparison.svg|A comparison of the letter O and the number 0|right]]

Traditionally, many print typefaces made the capital letter [[O]] more rounded than the narrower, elliptical digit 0.<ref name="bemer"/> [[Typewriter]]s originally made no distinction in shape between O and 0; some models did not even have a separate key for the digit 0. The distinction came into prominence on modern character [[Visual display unit|displays]].<ref name="bemer"/>

The digit 0 with a dot in the centre seems to have originated as an option on [[IBM 3270]] displays. Its appearance has continued with [[Taligent]]'s command line typeface [[Andalé Mono]]. One variation used a short vertical bar instead of the dot. This could be confused with the [[Greek alphabet|Greek letter]] [[Theta]] on a badly focused display, but in practice there was no confusion because theta was not (then) a displayable character and very little used anyway.

An alternative, the [[slashed zero]] (looking similar to the letter O except for the slash), was primarily used in hand-written coding sheets before transcription to punched cards or tape, and is also used in old-style [[ASCII]] graphic sets descended from the default typewheel on the [[Teletype Model 33]] ASR. This form is similar to the symbol <math>\emptyset</math>, or "∅" ([[Unicode]] character U+2205), representing the [[empty set]], as well as to the letter [[Ø]] used in several [[North Germanic languages|Scandinavian languages]]. Some [[Burroughs Corporation|Burroughs]]/[[Unisys]] equipment displays a digit 0 with a ''reversed'' slash.

The opposing convention that has the letter O ''with'' a slash and the digit 0 ''without'' was advocated by [[SHARE (computing)|SHARE]], a prominent [[IBM]] user group,<ref name="bemer"/> and recommended by IBM for writing [[Fortran|FORTRAN]] programs,<ref name="einarsson"/> and by a few other early mainframe makers; this is even more problematic for Scandinavians because it means two of their letters collide. Others advocated the opposite convention,<ref name="bemer"/> including IBM for writing [[Algol]] programs.<ref name="einarsson"/> Another convention used on some early [[line printer]]s left digit 0 unornamented but added a tail or hook to the capital O so that it resembled an inverted [[Q]] (like U+213A [[℺]]) or cursive capital letter-O (<math>\mathcal O</math>).<ref name="bemer"/>

Some fonts designed for use with computers made one of the capital-O–digit-0 pair more rounded and the other more angular (closer to a rectangle). The [[TI-99/4A]] computer has a more angular capital O and a more rounded digit 0, whereas others made the choice the other way around.
[[File:Deutsches Kfz-Kennzeichen für Behördenfahrzeuge (Nummernbereich 3).jpg|thumb|German license plate with slit zeros]]

The typeface used on most European [[vehicle registration plate]]s distinguishes the two symbols partially in this manner (having a more rectangular or wider shape for the capital O than the digit 0), but in several countries a further distinction is made by slitting open the digit 0 on the upper right side (as in [[Vehicle registration plates of Germany|German plates]] using the ''[[FE-Schrift|fälschungserschwerende Schrift]]'', "forgery-impeding typeface").

Sometimes the digit 0 is used either exclusively, or not at all, to avoid confusion altogether. For example, confirmation numbers<ref name="SW"/> used by [[Southwest Airlines]] use only the capital letters O and I instead of the digits 0 and 1, while [[Canadian postal code]]s use only the digits 1 and 0 and never the capital letters O and I, although letters and numbers always alternate.

==Other==
{{gallery
|height=100
|width=100
|title=Other representations of zero
|File:7-segment abcdef.svg
|alt1=Usual appearance of zero on seven-segment displays
|Usual appearance of zero on seven-segment displays
|File:7-segment cdeg.svg
|alt2=Unusual smaller appearance of zero on seven-segment displays
|Unusual smaller appearance of zero on seven-segment displays
|File:ICS Zero.svg
|alt3=International maritime signal flag for zero
|[[International maritime signal flags|International maritime signal flag]] for 0
}}
On the [[seven-segment display]]s of calculators, watches, and household appliances, 0 is usually written with six line segments, though on some historical calculator models it was written with four line segments.

The international maritime signal flag has five plus signs in an X arrangement.

==Zero symbols in Unicode== <!-- If editing this list, FYI {{unichar}} now provides the canonical name automagically, so only the codepoint number is required. -->
{{Div col|colwidth=20em}}
* {{unichar|0030|DIGIT ZERO}}
* {{unichar|0660|ARABIC-INDIC DIGIT ZERO}}
* {{unichar|06DF|ARABIC SMALL HIGH ROUNDED ZERO}}
* {{unichar|06E0|ARABIC SMALL HIGH UPRIGHT RECTANGULAR ZERO}}
* {{unichar|06F0|EXTENDED ARABIC-INDIC DIGIT ZERO}}
* {{unichar|07C0|NKO DIGIT ZERO}}
* {{unichar|0966|DEVANAGARI DIGIT ZERO}}
* {{unichar|09E6|BENGALI DIGIT ZERO}}
* {{unichar|0A66|GURMUKHI DIGIT ZERO}}
* {{unichar|0AE6|GUJARATI DIGIT ZERO}}
* {{unichar|0B66|ORIYA DIGIT ZERO}}
* {{unichar|0BE6|TAMIL DIGIT ZERO}}
* {{unichar|0C66|TELUGU DIGIT ZERO}}
* {{unichar|0C78|TELUGU FRACTION DIGIT ZERO FOR ODD POWERS OF FOUR}}
* {{unichar|0CE6|KANNADA DIGIT ZERO}}
* {{unichar|0D66|MALAYALAM DIGIT ZERO}}
* {{unichar|0DE6|SINHALA LITH DIGIT ZERO}}
* {{unichar|0E50|THAI DIGIT ZERO}}
* {{unichar|0ED0|LAO DIGIT ZERO}}
* {{unichar|0F20|TIBETAN DIGIT ZERO}}
* {{unichar|0F33|TIBETAN DIGIT HALF ZERO}}
* {{unichar|1040|MYANMAR DIGIT ZERO}}
* {{unichar|1090|MYANMAR SHAN DIGIT ZERO}}
* {{unichar|17E0|KHMER DIGIT ZERO}}
* {{unichar|1810|MONGOLIAN DIGIT ZERO}}
* {{unichar|1946|LIMBU DIGIT ZERO}}
* {{unichar|19D0|NEW TAI LUE DIGIT ZERO}}
* {{unichar|1A80|TAI THAM HORA DIGIT ZERO}}
* {{unichar|1A90|TAI THAM THAM DIGIT ZERO}}
* {{unichar|1B50|BALINESE DIGIT ZERO}}
* {{unichar|1BB0|SUNDANESE DIGIT ZERO}}
* {{unichar|1C40|LEPCHA DIGIT ZERO}}
* {{unichar|1C50|OL CHIKI DIGIT ZERO}}
* {{unichar|2070|SUPERSCRIPT ZERO}}
* {{unichar|2080|SUBSCRIPT ZERO}}
* {{unichar|2189|VULGAR FRACTION ZERO THIRDS}}
* {{unichar|24EA|CIRCLED DIGIT ZERO}}
* {{unichar|24FF|NEGATIVE CIRCLED DIGIT ZERO}}
* {{unichar|3007|IDEOGRAPHIC NUMBER ZERO}}
* {{unichar|3358|IDEOGRAPHIC TELEGRAPH SYMBOL FOR HOUR ZERO}}
* {{unichar|A620|VAI DIGIT ZERO}}
* {{unichar|A8D0|SAURASHTRA DIGIT ZERO}}
* {{unichar|A8E0|COMBINING DEVANAGARI DIGIT ZERO}}
* {{unichar|A900|KAYAH LI DIGIT ZERO}}
* {{unichar|A9D0|JAVANESE DIGIT ZERO}}
* {{unichar|A9F0|MYANMAR TAI LAING DIGIT ZERO}}
* {{unichar|AA50|CHAM DIGIT ZERO}}
* {{unichar|ABF0|MEETEI MAYEK DIGIT ZERO}}
* {{unichar|FF10|FULLWIDTH DIGIT ZERO}}
* {{unichar|1018A|GREEK ZERO SIGN}}
* {{unichar|104A0|OSMANYA DIGIT ZERO}}
* {{unichar|10D30|HANIFI ROHINGYA DIGIT ZERO}}
* {{unichar|11066|BRAHMI DIGIT ZERO}}
* {{unichar|110F0|SORA SOMPENG DIGIT ZERO}}
* {{unichar|11136|CHAKMA DIGIT ZERO}}
* {{unichar|111D0|SHARADA DIGIT ZERO}}
* {{unichar|112F0|KHUDAWADI DIGIT ZERO}}
* {{unichar|11366|COMBINING GRANTHA DIGIT ZERO}}
* {{unichar|11450|NEWA DIGIT ZERO}}
* {{unichar|114D0|TIRHUTA DIGIT ZERO}}
* {{unichar|11650|MODI DIGIT ZERO}}
* {{unichar|116C0|TAKRI DIGIT ZERO}}
* {{unichar|11730|AHOM DIGIT ZERO}}
* {{unichar|118E0|WARANG CITI DIGIT ZERO}}
* {{unichar|11950|DIVES AKURU DIGIT ZERO}}
* {{unichar|11C50|BHAIKSUKI DIGIT ZERO}}
* {{unichar|11D50|MASARAM GONDI DIGIT ZERO}}
* {{unichar|11DA0|GUNJALA GONDI DIGIT ZERO}}
* {{unichar|16A60|MRO DIGIT ZERO}}
* {{unichar|16B50|PAHAWH HMONG DIGIT ZERO}}
* {{unichar|16E80|MEDEFAIDRIN DIGIT ZERO}}
* {{unichar|1D2E0|MAYAN NUMERAL ZERO}}
* {{unichar|1D7CE|MATHEMATICAL BOLD DIGIT ZERO}}
* {{unichar|1D7D8|MATHEMATICAL DOUBLE-STRUCK DIGIT ZERO}}
* {{unichar|1D7E2|MATHEMATICAL SANS-SERIF DIGIT ZERO}}
* {{unichar|1D7EC|MATHEMATICAL SANS-SERIF BOLD DIGIT ZERO}}
* {{unichar|1D7F6|MATHEMATICAL MONOSPACE DIGIT ZERO}}
* {{unichar|1E140|NYIAKENG PUACHUE HMONG DIGIT ZERO}}
* {{unichar|1E2F0|WANCHO DIGIT ZERO}}
* {{unichar|1E950|ADLAM DIGIT ZERO}}
* {{unichar|1F100|DIGIT ZERO FULL STOP}}
* {{unichar|1F101|DIGIT ZERO COMMA}}
* {{unichar|1F10B|DINGBAT CIRCLED SANS-SERIF DIGIT ZERO}}
* {{unichar|1F10C|DINGBAT NEGATIVE CIRCLED SANS-SERIF DIGIT ZERO}}
* {{unichar|1F10D|CIRCLED ZERO WITH SLASH}}
* {{unichar|1FBF0|SEGMENTED DIGIT ZERO}}
* {{unichar|E0030|TAG DIGIT ZERO}}
{{Div col end}}
{{Contains special characters
| special    = uncommon [[Unicode]] characters
| fix        = Help:Multilingual support
| image      = Replacement character.svg
| link       = Specials (Unicode block)#Replacement character
| alt        = <?>
| compact    = yes
|section = table
}} <!-- Please leave this rubric at the end of the table because if placed at the top, only two columns can be formed. And in any case, the unusual symbols are at the end. -->

==See also==
*{{slink|Arabic numeral variations#Slashed zero}}
*{{slink|Regional handwriting variation#Arabic numerals}}
*[[Ø (disambiguation)]]<!-- a fairly comprehensive overview of characters and symbols that resemble Ø -->
*[[Zero width (disambiguation)]]

==References==
{{reflist|refs=
<ref name="bemer">{{cite journal |author-first=Robert William |author-last=Bemer |author-link=Robert William Bemer |title=Towards standards for handwritten zero and oh: much ado about nothing (and a letter), or a partial dossier on distinguishing between handwritten zero and oh |journal=Communications of the ACM |volume=10 |issue=8 |date=August 1967 |pages=513–518 |doi=10.1145/363534.363563|s2cid=294510 }}</ref>
<ref name="einarsson">{{cite web |author-first1=Bo |author-last1=Einarsson |author-first2=Yurij |author-last2=Shokin |title=Fortran 90 for the Fortran 77 Programmer |url=http://www.nsc.liu.se/~boein/f77to90/a7.html |at=Appendix 7: "The historical development of Fortran |date=2007-05-24 |url-status=live |archive-url=https://web.archive.org/web/20170228230542/https://www.nsc.liu.se/~boein/f77to90/a7.html |archive-date=2017-02-28}}</ref>
<ref name="SW">{{Cite web|url=http://southwest.com/content/travel_center/retrieveCheckinDoc.html|title=Check in for your Flight Reservation}}</ref> 
}}

{{Mathematical symbols notation language}}

[[Category:0 (number)]]
[[Category:Mathematical symbols]]