Slashed zero

The slashed zero is a representation of the number '0' (zero), with a slash through it. The slashed zero glyph is often used to distinguish the digit "zero" ("0") from the Latin script letter "O" anywhere that the distinction needs emphasis, particularly in encoding systems, scientific and engineering applications, computer programming (such as software development), and telecommunications. It thus helps to differentiate characters that would otherwise be homoglyphs. It was commonly used during the punched card era, when programs were typically written out by hand, to avoid ambiguity when the character was later typed on a card punch.

Unlike in the Scandinavian vowel 'Ø' and the "empty set" symbol '∅', the slash of a slashed zero usually does not extend past the ellipse in most typographic designs. However, the slashed zero is sometimes approximated by overlaying zero and slash characters, producing the character "0̸".

In character encoding terms, it has no explicit codepoint, but it is an alternate glyph (in addition to the open zero glyph) for the zero character.

The slashed zero long predates computers, and is known to have been used in the twelfth and thirteenth centuries. It is used in many Baudot teleprinter applications, specifically the keytop and typepallet that combines "P" and slashed zero. Additionally, the slashed zero is used in many ASCII graphic sets descended from the default typewheel on the Teletype Model 33.

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