|In Unicode||U+0023 # NUMBER SIGN (#)|
|Different from||U+266F ♯ MUSIC SHARP SIGN|
U+2317 ⌗ VIEWDATA SQUARE
U+22D5 ⋕ EQUAL AND PARALLEL TO
|See also||U+00A3 £ POUND SIGN|
U+2116 № NUMERO SIGN
The symbolis known variously in English-speaking regions as the number sign, hash, or pound sign. The symbol has historically been used for a wide range of purposes including the designation of an ordinal number and as a ligatured abbreviation for pounds avoirdupois – having been derived from the now-rare .
Since 2007, widespread usage of the symbol to introduce metadata tags on social media platforms has led to such tags being known as "hashtags", and from that, the symbol itself is sometimes called a hashtag.
The symbol is distinguished from similar symbols by its combination of level horizontal strokes and right-tilting vertical strokes.
It is believed that the symbol traces its origins to the symbol,[a] an abbreviation of the Roman term libra pondo, which translates as "pound weight". This abbreviation was printed with a dedicated ligature type element, with a horizontal line across, so that the lowercase letter would not be mistaken for the numeral . Ultimately, the symbol was reduced for clarity as an overlay of two horizontal strokes "=" across two slash-like strokes "//".
The symbol is described as the "number" character in an 1853 treatise on bookkeeping, and its double meaning is described in a bookkeeping text from 1880. The instruction manual of the Blickensderfer model 5 typewriter (c. 1896) appears to refer to the symbol as the "number mark". Some early-20th-century U.S. sources refer to it as the "number sign", although this could also refer to the numero sign. A 1917 manual distinguishes between two uses of the sign: "number (written before a figure)" and "pounds (written after a figure)". The use of the phrase "pound sign" to refer to this symbol is found from 1932 in U.S. usage. The term hash sign is found in South African writings from the late 1960s and from other non-North-American sources in the 1970s.
The symbol appears to have been used primarily in handwritten material; in the printing business, the numero symbol (№) and barred-lb (℔) were used for "number" and "pounds" respectively.[where?]
For mechanical devices, the symbol appeared on the keyboard of the Remington Standard typewriter (c. 1886). It appeared in many of the early teleprinter codes and from there was copied to ASCII, which made it available on computers and thus caused many more uses to be found for the character. The symbol was introduced on the bottom right button of touch-tone keypads in 1968, but that button was not extensively used until the advent of large-scale voicemail (PBX systems, etc.) in the early 1980s.
One of the uses in computers was to label the following text as having a different interpretation (such as a command or a comment) from the rest of the text. It was adopted for use within internet relay chat (IRC) networks circa 1988 to label groups and topics. This usage inspired Chris Messina to propose a similar system to be used on Twitter to tag topics of interest on the microblogging network; this became known as a hashtag. Although used initially and most popularly on Twitter, hashtag use has extended to other social media sites.
Pound sign or pound
Hash, hash mark, hashmark
#!is "hash, bang" or "shebang".
Octothorp, octothorpe, octathorp, octatherp
#instead, as does most documentation..
When ⟨#⟩ prefixes a number, it is read as "number". "A #2 pencil", for example, indicates "a number-two pencil". The abbreviations 'No.' and '№' are used commonly and interchangeably. The use of ⟨#⟩ as an abbreviation for "number" is common in informal writing, but use in print is rare. Where Americans might write "Symphony #5", British and Irish people usually write "Symphony No. 5".
When ⟨#⟩ is after a number, it is read as "pound" or "pounds", meaning the unit of weight. The text "5# bag of flour" would mean "five-pound bag of flour". The abbreviations "lb." and "℔" are used commonly and interchangeably. This usage is rare outside North America, where 'lb' or 'lbs' is used.
⟨#⟩ is not a replacement for the pound sign ⟨£⟩, but British typewriters and keyboards have a £ key where American keyboards have a # key. Many early computer and teleprinter codes (such as BS 4730 (the UK national variant of the ISO/IEC 646 character set) substituted '£' for '#' to make the British versions, thus it was common for the same binary code to display as
# on US equipment and
£ on British equipment ('$' was not substituted to avoid confusing dollars and pounds in financial communications).
#introduces a comment that goes to the end of the line. The combination
#!at the start of an executable file is a "shebang", "hash-bang" or "pound-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.
#!is the symbol of the CrunchBang Linux distribution.
#is used as a modifier to array syntax to return the index number of the last element in the array, e.g., an array's last element is at
$array[$#array]. The number of elements in the array is
$#array + 1, since Perl arrays default to using zero-based indices. If the array has not been defined, the return is also undefined. If the array is defined but has not had any elements assigned to it, e.g.,
@array = (), then
−1. See the section on Array functions in the Perl language structure article.
#is used to start a preprocessor directive. Inside macros, after
#define, it is used for various purposes; for example, the double pound (hash) sign
##is used for token concatenation.
#is placed by convention at the end of a command prompt to denote that the user is working as root.
#is used in a URL of a web page or other resource to introduce a "fragment identifier" – an id which defines a position within that resource. In HTML, this is known as an anchor link. For example, in the URL
https://en.wikipedia.org/wiki/Number_sign#Computingthe portion after the
Computing) is the fragment identifier, in this case denoting that the display should be moved to show the tag marked by
<span id="Computing">...</span>in the HTML.
#precedes the name of every channel that is available across an entire IRC network.
#is sometimes used to denote a permalink for that particular weblog entry.
#is often used to introduce numbered list items.
#is used in the Modula-2 and Oberon programming languages designed by Niklaus Wirth and in the Component Pascal language derived from Oberon to denote the not equal symbol, as a stand-in for the mathematical unequal sign , being more intuitive than
!=. For example:
IF i # 0 THEN ...
#is used for attributes such as in
#is the operator used to call a method.
#is a dispatching read macro character used to extend the S-expression syntax with short cuts and support for various data types (complex numbers, vectors and more).
#is the prefix for certain syntax with special meaning.
#, 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.
#, when used as a variable, becomes a pure function (a placeholder that is mapped to any variable meeting the conditions).
#, when prefixing a number, references an arguments for a user defined command. For instance
#is used with the
@seetag to introduce or separate a field, constructor, or method member from its containing class.
#is used to denote immediate mode addressing, e.g.,
LDA #10, which means "load accumulator A with the value 10" in MOS 6502 assembly language.
#is used to identify a color specified in hexadecimal format, e.g.,
#FFAA00. This usage comes from X11 color specifications, which inherited it from early assembler dialects that used
#to prefix hexadecimal constants, e.g.: ZX Spectrum Z80 assembly.
#. Lines starting with characters other than "#" are treated as comments.
@) are used as additional letters in identifiers, labels and data set names.
#is the Tally or Count function, and similarly in Lua,
#can be used as a shortcut to get the length of a table, or get the length of a string. Due to the ease of writing "#" over longer function names, this practice has become standard in the Lua community.
#is a reference to the root namespace while
##is a reference to the current space's parent namespace.
/d/ → [t] / _#means that becomes when it is the last segment in a word (i.e. when it appears before a word boundary).
In Unicode, several # characters are assigned. Other attested names in Unicode are: pound sign, hash, crosshatch, octothorpe.
|Unicode name||NUMBER SIGN||FULLWIDTH NUMBER SIGN||SMALL NUMBER SIGN|
|UTF-8||35||23||239 188 131||EF BC 83||239 185 159||EF B9 9F|
|GB 18030||35||23||163 163||A3 A3||169 124||A9 7C|
|Numeric character reference||#
|Named character reference||#|
|ASCII and extensions||35||23|
|EBCDIC (037, 500, UTF)||123||7B|
|Shift JIS||35||23||129 148||81 94|
|EUC-JP||35||23||161 244||A1 F4|
|EUC-KR / UHC||35||23||163 163||A3 A3|
|Big5||35||23||161 173||A1 AD||161 204||A1 CC|
|EUC-TW||35||23||161 236||A1 EC||162 173||A2 AD|
|Unicode name||KEYCAP NUMBER SIGN|
|Unicode||35 65039 8419||U+0023+FE0F+20E3|
|UTF-8||35 239 184 143 226 131 163||23 EF B8 8F E2 83 A3|
|GB 18030||35 132 49 130 53 129 54 184 54||23 84 31 82 35 81 36 B8 36|
|Numeric character reference||#
|Shift JIS (NTT Docomo)||249 133||F9 85|
|Shift JIS (SoftBank 3G)||247 176||F7 B0|
|Shift JIS (au by KDDI)||244 137||F4 89|
|7-bit JIS (au by KDDI and others)||123 105||7B 69|
At least three orthographically distinct number signs from other languages are also assigned:
On the standard US keyboard layout, thesymbol is ⇧ Shift+3. On standard UK and some other European keyboards, the same keystrokes produce the pound (sterling) sign, symbol, and # may be moved to a separate key above the right shift key. If there is no key, the symbol can be produced on Windows with Alt+35, on Mac OS with ⌥ Opt+3, and on Linux with Compose++.
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.
It is best to use the 'number mark' for plus; the hyphen for minus, and two hyphens for the sign =
business symbols pound.
In Australia, however, it was better known as the 'hash' sign and only used to mean 'number'.