Number sign

Number sign is a name for the symbol #, which is used for a variety of purposes including the designation of a number (for example, "#1" stands for "number one"). "Number sign" is the preferred Unicode name for the code point. Its Unicode code point is U+0023, and its ASCII value is 0x23 (hexadecimal).

In most English-speaking countries outside North America, the symbol is usually called the hash mark, hash sign, or hash symbol. It is also a "hash key" on touch-tone phones in these areas. As used in the United States on touch-tone telephones, the key on phones is referred to as the pound key, with the symbol being called the pound sign. In Canada, this key is most frequently called the number sign key. Beginning in the 1960s, telephone engineers have attempted to coin a special name for this symbol, with variant spellings including octothorp, octothorpe, octathorp, and octatherp. None has become universal or widely accepted.

In non-English speaking nations, other names for this symbol are also used. In many parts of the world, including parts of Europe, Canada, Australia, and Russia, "number sign" is the name of the "numero" sign № (Unicode code point U+2116), which is often written simply as No. In some of those countries, the # sign is not used to indicate a number.

The symbol is easily confused with the musical symbol called sharp (♯). In both marks, there are two pairs of lines that are parallel to each other, and each mark has one pair of lines which is rectilinear and one pair which is not. The key difference is that the sharp has perpendicular vertical strokes, with two diagonal "horizontal" strokes (that is, the horizontals are not truly horizontal, in the sharp). By contrast, the number sign (#) does have two truly horizontal strokes, combined with two diagonal "verticals" (or double slashes, as in this sign, these "vertical" strokes are not perfectly vertical).

Usage in North America

The mainstream use in the U.S. as follows: when it precedes a number, it is read as "number", as in "a #2 pencil" (spoken aloud as: "a number two pencil"); however, when it follows a number it is read as "pounds" referring to the unit of weight, as in "5# of sugar" (spoken aloud as "five pounds of sugar"). The first form is more widely used by the general population while the second form is more specifically used in the food service and grocery/produce industries, or other fields where units of pounds (as weight) need to be hand-written frequently or repetitively.

Naming conventions in North America

In most regions of the United States, the symbol is traditionally called the pound sign, but in others, the number sign. This derives from a series of abbreviations for pound, the unit of weight. At first "lb." was used; however, printers later designed a font containing a special symbol of an "lb" with a line through the verticals so that the lowercase letter "l" would not be mistaken for the numeral/digit "1". Unicode character U+2114 (℔) is called the "LB Bar Symbol", and it is a cursive development of this symbol. Ultimately, the symbol was reduced for clarity as an overlay of two horizontal strokes "=" across two forward-slash-like strokes "//".

In Canada, the symbol is traditionally referred to as the number sign. Major telephone equipment manufacturers, such as Nortel, have an option in their programming to indicate Canadian Pronunciation, which in turn instructs the system to say "Number Sign" to callers instead of "Pound Sign." This same option causes the system to say "zed" instead of the United States' "zee" for the letter Z.

Usage in the UK

The hash sign is rarely used in the UK to designate a number like in North America. It is never used to refer to pounds as a unit of weight, as lb is commonly used for this. Furthermore, # would never be called the pound sign in the UK since the term "pound sign" is universally understood to mean the £ (pound sterling) character.

Other names in English

The symbol has many other names (and uses) in English. (Those in bold are listed as alternative names in the Unicode documentation.)

• Comment sign
  • from its use in many shell scripts and some programming languages (such as Perl) to introduce comments.

• Crosshatch
  • describing the form of the symbol.

• Crunch
  • named for its resemblance to broken glass, and following the convention of giving punctuation marks onomatopoetic nicknames (as in 'bang' for the exclamation mark, 'ding' for the dollar sign, and 'splat' for the asterisk).

• Fence, gate, grid, gridlet
  • describing the resemblance of such objects to this glyph.

• hash / hash mark / hash sign
  • "Hash" is a common name for the mark used in the English-speaking world outside North America.
  • In Ireland, the UK, Australia, India and New Zealand, "hash key" refers to the # button on touch-tone telephones; "Please press the hash key."

• Hex
  • Common usage in Singapore and Malaysia – as spoken by many recorded telephone directory-assistance menus: 'Please enter your phone number followed by the hex (sic: number sign) key'

• mesh
  • introduced in the so-called "tonsil" (a humorous play on "appendix") of the Intercal reference manual, and often reproduced in The Hacker's Dictionary.

• octothorp / octothorpe / octathorp / octatherp
  • See wiktionary:octothorpe for etymology; see also www.octothorp.us.
  • See Doug Kerr's Octatherp article for detailed alternative etymology of octotherp.
  • See Encore magazine article "Pressing matters: touch-tone phones spark debates" for another attribution to Bell engineers, by 1968. Lauren Asplund, who provided the article, says that he and a colleague were the source of octothorp at AT&T engineering in New York in 1964. The term octothorpe was coined by Bell Labs but opposed by Western Electric and therefore never gained any popularity.[1]
  • The Merriam-Webster New Book of Word Histories, 1991, has a long article that is consistent with Doug Kerr's essay, in that it says octotherp was the original spelling, and that the word arose in the 1960s among telephone engineers.
  • The first appearance of octothorp in a U.S. patent is in a 1973 filing which also refers to the asterisk (*) as a sextile.
  • http://www.worldwidewords.org/weirdwords/ww-oct1.htm tells of three possible etymologies, none corroborated, and says it was not in print until 1974.

• pound
  • Used as the symbol for the pound (the unit of mass) in the U.S. (where lb. would be used in the UK and Canada; note that lb. or lbs. is common in the U.S. as well and is used by the general public more often than #). It is never called the pound sign in the UK, where that term always denotes the symbol for pounds sterling (£) rather than that for pounds weight (lb).
    • Keith Gordon Irwin, in The Romance of Writing p. 125, says: "The Italian libbra (from the old Latin word libra, 'balance') represented a weight almost exactly equal to the avoirdupois pound of England. The Italian abbreviation of lb with a line drawn across the letters was used for both weights. The business clerks' hurried way of writing the abbreviation appears to have been responsible for the # sign used for pound."
  • To add to the confusion, the pound symbol '#' appears above the numeral 3 on a US-English layout keyboard but on a UK-English keyboard the character above the 3 is the pound sign - '£'
  • Used in the U.S. and Canada on touch-tone telephones – "Please press the pound key"

• sharp
  • resemblance to the glyph used in music notation, U+266F (♯). Since most fonts do not contain the sharp sign, many works use the number sign as an acceptably erroneous orthographic error.
  • so called in the name of the Microsoft-invented programming language, C#. However Microsoft says at Frequently Asked Questions About C#:
    It's not the "hash" (or pound) symbol as most people believe. It's actually supposed to be the musical sharp symbol. However, because the sharp symbol is not present on the standard keyboard, it's easier to type the hash ("#") symbol. The name of the language is, of course, pronounced "see sharp".
    According to the ECMA-334 C# Language Specification, section 6, Acronyms and abbreviations, the name of the language is written "C#" ("LATIN CAPITAL LETTER C (U+0043) followed by the NUMBER SIGN # (U+0023)") and pronounced "C Sharp".
  • In computing a shebang is the inexact contraction of sharp and bang the typical names of the # and ! signs used at the beginning of executable text files. Also sometimes spoken as "hash-bang," with similar derivation.

• Space
  • used by editors to indicate where space should be inserted in a proof. This can mean (1) a line space (the space between two adjacent lines denoted by line # in the margin), (2) a hair space (the space between two letters in a word, denoted by hr #) (3) a word space, or letter space (the space between two words on a line, two letter spaces being ##). Em- and en-spaces (being the length of a letter m and n, respectively) are indicated by a square-shaped em- or en-quad character (? and ??, respectively).

• Square
  • occasionally used in the UK (e.g. sometimes in BT publications and automatic messages) – especially during the Prestel era, when the symbol was a page address delimiter
  • the International Telecommunications Union specification ITU-T E.161 3.2.2 states: "The # is to be known as a 'square' or the most commonly used equivalent term in other languages."

• Tic-Tac-Toe sign
  • A colloqialism used for identification, based on the symbol's similarity to the board layout of Tic Tac Toe.

Telecommunications and Internet usage

• Telephone Keypads: as found on a telephone keypad, # is one of the two standard special keys beyond digits 0 to 9 (the other being the star key, *). It generates a compound tone mixing 941 Hz and 1477 Hz. Its function depends on services provided by a given telephone-based service.

• URL: # is used immediately after the URL of a webpage or other resource to introduce a "fragment identifier" – a name or id which defines a position within that resource or a section of the document. For example, in the URL http://en.wikipedia.org/wiki/Number_sign#Other_uses the portion after the # (Other_uses) is the fragment identifier (a link such as this will take you to a section in a web page, such as the 'Other uses' section of this article). A relative reference to the fragment from within the document itself can start with the number sign, and consist of just the fragment identifier: <a href="#top">TOC</a> refers to an anchor named "top" on the current web page.

• Internet Relay Chat: on (IRC) servers, # precedes the name of every channel that is available across an entire IRC network.

• HTML code: In blogs, # is sometimes used to denote a permalink for that particular weblog entry.

• Unix Code: In the Unix shell, # is placed by convention at the end of a command prompt to indicate that the user is working as root. In Unix scripting, for example, it is used in combination with an exclamation mark ("#!") to produce a "shebang" or "hash-bang", used to tell the operating system which program to use to run the script (see magic number).

Other uses

• Press releases: the notation "###" indicates "end", i.e. that there is no further copy to come.

• Chess notation, # after a move denotes checkmate, being easier to type than the traditional ++.

• Prescription drug delimiter: in some countries, such as Norway, # is used as a delimiter between different drugs on medical prescriptions.

• Denote "hashtag": on social networking sites such as Twitter, the hash symbol is used to denote a metadata tag, or "hashtag".

• Copy writing and Editing: Technical writers often use three hash signs ("###") as a marker in text where more content will be added or there are errors to be corrected.

• Sometimes used by bloggers and forum users as a 'middle finger' gesture. It's believed this usage stems from the practice of replacing the center letters of curse words in magazines and newspapers with symbols such and #,~,! etc.

• Mining: In underground mining, the hash sign is sometimes used as a shorthand for "seam" or "shaft". An example would be "4#", which would mean "four shaft" or "four seam" depending on the context.

• Medical shorthand: # is often used as medical shorthand for 'fracture'.

External links

• Encore magazine article "Pressing matters: touch-tone phones spark debates" for another attribution to Bell engineers.