Symbols for zero

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

Contents

Glyphs

Text figures 036.svg

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).

A comparison of the letter O and the number 0 Zero o comparison.svg
A comparison of the letter O and the number 0

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 [1] Typewriters originally made no distinction in shape between O and 0; some models did not even have a separate key for the digit 0.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 , 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 (). [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 Deutsches Kfz-Kennzeichen fur Behordenfahrzeuge (Nummernbereich 3).jpg
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] [ better source needed ] 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

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

See also

References

  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.
  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.
  3. "Check in for your Flight Reservation".