Symbols for zero

Last updated August 14, 2023

The modern numerical digit 0 is usually written as a circle, an ellipse or a rounded square or rectangle.

Glyphs

In most modern typefaces, 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).

Traditionally, many print typefaces made the capital letter O more rounded than the narrower, elliptical digit 0.^[1] Typewriters originally made no distinction in shape between O and 0; some models did not even have a separate key for the digit 0.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 displays.^[1]

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 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 $\emptyset$ , or "∅" (Unicode character U+2205), representing the empty set, as well as to the letter Ø used in several Scandinavian languages. Some 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, a prominent IBM user group,^[1] and recommended by IBM for writing FORTRAN programs,^[2] 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,^[1] including IBM for writing Algol programs.^[2] Another convention used on some early line printers 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 ( ${\mathcal {O}}$ ).^[1]

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.

German license plate with slit zeros

The typeface used on most European vehicle registration plates 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 German plates using the 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^[3] used by Southwest Airlines use only the capital letters O and I instead of the digits 0 and 1, while Canadian postal codes use only the digits 1 and 0 and never the capital letters O and I, although letters and numbers always alternate.

Other

Other representations of zero

Usual appearance of zero on seven-segment displays
Unusual smaller appearance of zero on seven-segment displays
International maritime signal flag for 0

On the seven-segment displays 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

U+00300DIGIT ZERO
U+0660٠ARABIC-INDIC DIGIT ZERO
U+06DF۟ARABIC SMALL HIGH ROUNDED ZERO
U+06E0۠ARABIC SMALL HIGH UPRIGHT RECTANGULAR ZERO
U+06F0۰EXTENDED ARABIC-INDIC DIGIT ZERO
U+07C0߀NKO DIGIT ZERO
U+0966०DEVANAGARI DIGIT ZERO
U+09E6০BENGALI DIGIT ZERO
U+0A66੦GURMUKHI DIGIT ZERO
U+0AE6૦GUJARATI DIGIT ZERO
U+0B66୦ORIYA DIGIT ZERO
U+0BE6௦TAMIL DIGIT ZERO
U+0C66౦TELUGU DIGIT ZERO
U+0C78౸TELUGU FRACTION DIGIT ZERO FOR ODD POWERS OF FOUR
U+0CE6೦KANNADA DIGIT ZERO
U+0D66൦MALAYALAM DIGIT ZERO
U+0DE6෦SINHALA LITH DIGIT ZERO
U+0E50๐THAI DIGIT ZERO
U+0ED0໐LAO DIGIT ZERO
U+0F20༠TIBETAN DIGIT ZERO
U+0F33༳TIBETAN DIGIT HALF ZERO
U+1040၀MYANMAR DIGIT ZERO
U+1090႐MYANMAR SHAN DIGIT ZERO
U+17E0០KHMER DIGIT ZERO
U+1810᠐MONGOLIAN DIGIT ZERO
U+1946᥆LIMBU DIGIT ZERO
U+19D0᧐NEW TAI LUE DIGIT ZERO
U+1A80᪀TAI THAM HORA DIGIT ZERO
U+1A90᪐TAI THAM THAM DIGIT ZERO
U+1B50᭐BALINESE DIGIT ZERO
U+1BB0᮰SUNDANESE DIGIT ZERO
U+1C40᱀LEPCHA DIGIT ZERO
U+1C50᱐OL CHIKI DIGIT ZERO
U+2070⁰SUPERSCRIPT ZERO
U+2080₀SUBSCRIPT ZERO
U+2189↉VULGAR FRACTION ZERO THIRDS
U+24EA⓪CIRCLED DIGIT ZERO
U+24FF⓿NEGATIVE CIRCLED DIGIT ZERO
U+3007〇IDEOGRAPHIC NUMBER ZERO
U+3358㍘IDEOGRAPHIC TELEGRAPH SYMBOL FOR HOUR ZERO
U+A620꘠VAI DIGIT ZERO
U+A8D0꣐SAURASHTRA DIGIT ZERO
U+A8E0꣠COMBINING DEVANAGARI DIGIT ZERO
U+A900꤀KAYAH LI DIGIT ZERO
U+A9D0꧐JAVANESE DIGIT ZERO
U+A9F0꧰MYANMAR TAI LAING DIGIT ZERO
U+AA50꩐CHAM DIGIT ZERO
U+ABF0꯰MEETEI MAYEK DIGIT ZERO
U+FF10０FULLWIDTH DIGIT ZERO
U+1018A𐆊GREEK ZERO SIGN
U+104A0𐒠OSMANYA DIGIT ZERO
U+10D30𐴰HANIFI ROHINGYA DIGIT ZERO
U+11066𑁦BRAHMI DIGIT ZERO
U+110F0𑃰SORA SOMPENG DIGIT ZERO
U+11136𑄶CHAKMA DIGIT ZERO
U+111D0𑇐SHARADA DIGIT ZERO
U+112F0𑋰KHUDAWADI DIGIT ZERO
U+11366𑍦COMBINING GRANTHA DIGIT ZERO
U+11450𑑐NEWA DIGIT ZERO
U+114D0𑓐TIRHUTA DIGIT ZERO
U+11650𑙐MODI DIGIT ZERO
U+116C0𑛀TAKRI DIGIT ZERO
U+11730𑜰AHOM DIGIT ZERO
U+118E0𑣠WARANG CITI DIGIT ZERO
U+11950𑥐DIVES AKURU DIGIT ZERO
U+11C50𑱐BHAIKSUKI DIGIT ZERO
U+11D50𑵐MASARAM GONDI DIGIT ZERO
U+11DA0𑶠GUNJALA GONDI DIGIT ZERO
U+16A60𖩠MRO DIGIT ZERO
U+16B50𖭐PAHAWH HMONG DIGIT ZERO
U+16E80𖺀MEDEFAIDRIN DIGIT ZERO
U+1D2E0𝋠MAYAN NUMERAL ZERO
U+1D7CE𝟎MATHEMATICAL BOLD DIGIT ZERO
U+1D7D8𝟘MATHEMATICAL DOUBLE-STRUCK DIGIT ZERO
U+1D7E2𝟢MATHEMATICAL SANS-SERIF DIGIT ZERO
U+1D7EC𝟬MATHEMATICAL SANS-SERIF BOLD DIGIT ZERO
U+1D7F6𝟶MATHEMATICAL MONOSPACE DIGIT ZERO
U+1E140𞅀NYIAKENG PUACHUE HMONG DIGIT ZERO
U+1E2F0𞋰WANCHO DIGIT ZERO
U+1E950𞥐ADLAM DIGIT ZERO
U+1F100🄀DIGIT ZERO FULL STOP
U+1F101🄁DIGIT ZERO COMMA
U+1F10B🄋DINGBAT CIRCLED SANS-SERIF DIGIT ZERO
U+1F10C🄌DINGBAT NEGATIVE CIRCLED SANS-SERIF DIGIT ZERO
U+1F10D🄍CIRCLED ZERO WITH SLASH
U+1FBF0🯰SEGMENTED DIGIT ZERO
U+E0030TAG DIGIT ZERO

You may need rendering support to display the uncommon Unicode characters in this table correctly.

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References

1 2 3 4 5 Bemer, Robert William (August 1967). "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". Communications of the ACM. 10 (8): 513–518. doi:10.1145/363534.363563. S2CID 294510.
1 2 Einarsson, Bo; Shokin, Yurij (2007-05-24). "Fortran 90 for the Fortran 77 Programmer". Appendix 7: "The historical development of Fortran. Archived from the original on 2017-02-28.
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[bemer-1] 1 2 3 4 5 Bemer, Robert William (August 1967). "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". Communications of the ACM. 10 (8): 513–518. doi:10.1145/363534.363563. S2CID 294510.

[einarsson-2] 1 2 Einarsson, Bo; Shokin, Yurij (2007-05-24). "Fortran 90 for the Fortran 77 Programmer". Appendix 7: "The historical development of Fortran. Archived from the original on 2017-02-28.

[SW-3] "Check in for your Flight Reservation".

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