Number sign

Template:Distinguish2 #

Number sign is a name for the symbol #, which is used for a variety of purposes including, in some countries, 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 35 (0x23 in hexadecimal). The html entity is # or #.

In the United States, the symbol is usually called the pound sign, and the key bearing this symbol on touch-tone phones is called the pound key. In Canada, this key is most frequently called the number sign key. In most English-speaking countries outside North America, the symbol is usually called the hash, and the corresponding telephone key is the hash 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 (or equivalents in local languages) refers instead to the "numero" sign № (Unicode code point U+2116), which is often written simply as No.

The symbol is easily confused with the musical symbol called sharp (♯). In both symbols, there are two pairs of parallel lines. The key difference is that the number sign has compulsory true-horizontal strokes while the sharp sign does not have them. Instead, the sharp sign has two slanted parallel lines which rise from left-to-right. Both signs may have true vertical lines; however, they are compulsory in the sharp, but optional in the number sign (#) depending on typeface or handwriting style. Thus only the number sign may have an italic appearance.

Usage and naming conventions in North America

Mainstream use in the U.S.A. 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. Most others use the abbreviation "lb." or "lbs."

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 "L B 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.

In engineering circles, the pound sign followed by 'per square inch' is used to describe pounds per square inch.

Usage in the UK

In the UK, the symbol is most often called the hash. It is never used to refer to pounds as a unit of weight (lb is commonly used for this) or currency. Furthermore, it is never called the pound sign since the term "pound sign" is understood to mean the currency symbol, £, for pound sterling.

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, South Africa and New Zealand, "hash key" refers to the # button on touch-tone telephones: "Please press the hash key."
  • Very common inside North America when reading computer text out loud when it is used to indicate a comment.

• 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 (a unit of weight) 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, considering it an acceptable 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".

• 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 colloquialism used for identification, based on the symbol's similarity to the board layout of tic-tac-toe (noughts and crosses).

In mathematics

• In set theory, #S is the cardinality of the set S. That is, for a set $S=\{s_{1},s_{2},s_{3},\dots ,s_{n}\},$ #S = n.
• In topology, where A and B are manifolds, A#B is the manifolds' connected sum. In knot theory (a branch of topology), where A and B are knots, A#B is the knots' knot sum.
• In number theory, n# is the primorial of n.

Computing

• # is one of the two standard special keys beyond digits 0 to 9 on a telephone keypad (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, but it is often used to indicate the end of a variable-length number such as an account number or item number.
• In many scripting languages and data file formats, especially ones that originated on Unix, the # introduces a comment that goes to the end of the line. The combination #! at the start of an executable file is a "shebang" or "hash-bang", used to tell the operating system which program to use to run the script (see magic number). This combination was chosen so it would be a comment in the scripting languages.
• In the C preprocessor, # is used to start a preprocessor directive.
• In the Unix shell, # is placed by convention at the end of a command prompt to indicate that the user is working as root.
• # is used in a URL of a webpage or other resource to introduce a "fragment identifier" – an id which defines a position within that resource. For example, in the URL http://en.wikipedia.org/wiki/Number_sign#Computing the portion after the # (Computing) is the fragment identifier, in this case indicating that the display should be moved to show the tag marked by <a name="Computing">...</a> in the HTML
• Internet Relay Chat: on (IRC) servers, # precedes the name of every channel that is available across an entire IRC network.
• In blogs, # is sometimes used to denote a permalink for that particular weblog entry.
• On social networking sites such as Twitter, # is used to denote a metadata tag, or "hashtag".
• In lightweight markup languages, such as wikitext, # is often used to introduce numbered list items.
• In OCaml, # is the operator used to call a method.
• In Common Lisp and Scheme, # is the prefix for certain syntax with special meaning.
• In Standard ML, #, when prefixed to a field name, becomes a projection function (function to access the field of a record or tuple); also, # prefixes a string literal to turn it into a character literal.
• In LaTeX, #, when prefixing a number, references an arguments for a user defined command. For instance \newcommand{\code}[1]{\texttt{#1}}.

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 or Poland # is used as a delimiter between different drugs on medical prescriptions.
• 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 is believed this usage stems from the practice of replacing the center letters of curse words in magazines and newspapers with symbols such as #,~,! 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'.
• In linguistic phonetics, # indicates a word boundary. For instance, /d/ -> [t] / _# means that /d/ becomes [t] when it is the last segment in a word (ie. when it appears before a word boundary).
• In linguistic syntax, # before an example sentence indicates that the sentence, although grammatical, does not convey the intended meaning.
• In Teletext and DVB subtitles in the UK, the # symbol is used to mark text that is sung either by a character or heard in background music. eg. # For he's a jolly good fellow #

On the keyboard

On standard US keyboard layouts, the # symbol is Shift+3. On standard UK keyboards, Shift+3 generates the pound currency symbol (£), and # is moved to a separate key above the right shift. On UK Apple Mac keyboards, # is generated by Option+3. On standard European keyboards, AltGr+3 generates the # symbol. Under Microsoft Windows and MS-DOS it can be also generated through the Alt code Alt-35.

External links

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