Slashed zero

A slashed zero is a special way to write the number zero with a line through it. This helps tell the difference between the number zero and the letter O.

People use this symbol in many places, like in computers, science, and engineering. It was very common a long time ago when people wrote programs on special cards by hand. The line through the zero made sure there was no confusion when the cards were read by machines.

This symbol is still useful today in many kinds of technology and writing where mixing up zero and O could cause problems.

Usage

The slashed zero is a special way to write the number zero with a line through it. This helps people not mix it up with the letter "O". Many different jobs and areas use this special zero.

Computer programmers, people who talk on amateur radio, and those in the military all use the slashed zero. It was also used in old weather reporting systems. In science, it can help tell the number zero from the symbol for oxygen. Doctors and nurses use it too, so they don’t confuse zero with the letter O when they write about health. You can even see this special zero on car license plates in New Zealand.

History

The slashed zero is a zero with a line through it. It has been used since the 1200s and 1300s.

When typewriters were popular, there was no special key for the slashed zero. People made it by typing an "O" or a zero, then using backspace, and adding a slash.

The slashed zero was also used in old telegraph machines and early computer systems. In the 1970s and 1980s, it became popular in computer culture. Some bands and artists used it in their names and artwork, like the band Underground Zerø and the artwork of Young-Hae Chang Heavy Industries. It helped people tell the number zero apart from the letter "O" in writing and coding.

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Similar symbols

The slashed zero can look like other symbols and this may cause confusion. For a full list of similar symbols, you can see the disambiguation page for the symbol Ø.

Representation in Unicode

In Unicode, the slashed zero is a special way to show the number zero (0), which is the Arabic digit. By adding something called Variation Selector 1 after the zero, we get a version with a short diagonal line through it, like this: 0︀.

This is different from another symbol that looks similar, used to mean the empty set. Unicode has its own way to show that symbol.

Before Unicode version 9.0, there wasn't a special code for the slashed zero. This meant that only certain fonts could show it, and you needed the right font on your system to see it properly.

Combining solidus

Before Unicode had a standard way to show the slashed zero, people used a trick with two characters: the normal zero followed by a small slash symbol. But this could sometimes look messy if the zero already had a slash in the font. There was no perfect way to always show an unslashed zero safely.

Rendering

If a font has a special feature called zero, it can show a slashed zero instead of a regular zero.

In HTML, you can make slashed zeros appear by using CSS rules like font-variant-numeric: slashed-zero or font-feature-settings: 'zero'. This makes the zero look like 0 on your screen.

Typography

In many font designs, the line through a slashed zero does not go past the round shape of the zero. This is different from some special symbols like the Scandinavian vowel "Ø", the empty set symbol "∅", and the diameter symbol "⌀".

However, in Japanese fonts, the line through the zero often goes beyond the round shape.

Older printers sometimes did not change the zero but made the letter O look like an upside-down Q or a fancy capital O.

In the Fixedsys font, the zero has two small lines inside it that look like a white "S".

In the FE-Schrift font, used on German car license plates, the zero is a rectangle with a small diagonal crack near the top right corner.

Typefaces

Some fonts on computers show a special zero with a line through it so it looks different from the letter O. Examples include Terminal on Windows, Consolas on newer Windows versions and Office, Menlo, Monaco, and SF Mono on macOS, and Roboto Mono.

Other fonts use a zero with a dot in the middle, such as DejaVu Sans Mono, Andale Mono, IBM Plex Mono, Source Code Pro, and Cascadia Code, which is the default font for Windows Terminal and Visual Studio Code.

Variations

The zero with a dot in the center started on IBM 3270 displays. It can look like the Greek letter theta, but they are different. On old screens, it might look like the number 8. Sometimes the dot can turn into a line.

IBM and some early computers used a letter O with a slash, while the digit 0 looked normal. This was hard for people from Denmark, the Faroe Islands, and Norway because their letters O and Ø looked too similar. Later, most machines changed it so the letter O looked normal and the digit zero had a slash. This was common from the 1970s to the 1990s. But today, many printers no longer use this slashed zero.

Some Burroughs/Unisys machines and the free typeface Atkinson Hyperlegible show a zero with a reversed slash, like the no symbol, 🛇.