| Mark: | |unicode = |see also = The symbol is known variously in English-speaking regions as the number sign,[1] hash,[2] or pound sign.[3] 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 .[4] Since 2007, widespread usage of the symbol to introduce metadata tags on social media platforms has led to such tags being known as "hashtags",[5] and from that, the symbol itself is sometimes called a hashtag.[6] The symbol is distinguished from similar symbols by its combination of level horizontal strokes and right-tilting vertical strokes. HistoryIt is believed that the symbol traces its origins to the symbol, an abbreviation of the Roman term libra pondo, which translates as "pound weight".[7] The abbreviation "lb" was printed as a dedicated ligature including a horizontal line across (which indicated abbreviation).[8] Ultimately, the symbol was reduced for clarity as an overlay of two horizontal strokes "=" across two slash-like strokes "//".[9] The symbol is described as the "number" character in an 1853 treatise on bookkeeping,[10] and its double meaning is described in a bookkeeping text from 1880.[11] The instruction manual of the Blickensderfer model 5 typewriter appears to refer to the symbol as the "number mark".[12] Some early-20th-century U.S. sources refer to it as the "number sign",[13] although this could also refer to the numero sign .[14] A 1917 manual distinguishes between two uses of the sign: "number (written before a figure)" and "pounds (written after a figure)".[15] The use of the phrase "pound sign" to refer to this symbol is found from 1932 in U.S. usage.[16] The term hash sign is found in South African writings from the late 1960s[17] and from other non-North-American sources in the 1970s. For mechanical devices, the symbol appeared on the keyboard of the Remington Standard typewriter .[18] 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.[19] This usage inspired Chris Messina to propose a similar system to be used on Twitter to tag topics of interest on the microblogging network;[20] [21] this became known as a hashtag. Although used initially and most popularly on Twitter, hashtag use has extended to other social media sites.[22] NamesNumber sign "Number sign" is the name chosen by the Unicode consortium. Most common in Canada[23] and the northeastern United States. American telephone equipment companies which serve Canadian callers often have an option in their programming to denote Canadian English, which in turn instructs the system to say number sign to callers instead of pound.[24] Pound sign or pound In the United States, the "#" key on a phone is commonly referred to as the pound sign, pound key, or simply pound. Dialing instructions to an extension such as #77, for example, can be read as "pound seven seven".[25] This name is rarely used outside the United States, where the term pound sign is understood to mean the currency symbol £.Hash, hash mark, hashmark In the United Kingdom,[26] Australia,[27] and some other countries, it is generally called a "hash" (probably from "hatch", referring to cross-hatching[28]). Programmers also use this term; for instance is "hash, bang" or "shebang".Hashtag Derived from the previous, the word "hashtag" is often used when reading social media messages aloud, indicating the start of a hashtag. For instance, the text "#foo" is often read out loud as "hashtag foo" (as opposed to "hash foo"). This leads to the common belief that the symbol itself is called hashtag. Twitter documentation refers to it as "the hashtag symbol".[29] Hex "Hex" is commonly used in Singapore and Malaysia, as spoken by many recorded telephone directory-assistance menus: "Please enter your phone number followed by the 'hex' key". The term "hex" is discouraged in Singapore in favour of "hash". In Singapore, a hash is also called "hex" in apartment addresses, where it precedes the floor number.[30] [31] , octothorpe, octathorp, octatherp Most scholars believe the word was invented by workers at the Bell Telephone Laboratories by 1968,[32] who needed a word for the symbol on the telephone keypad. Don MacPherson is said to have created the word by combining octo and the last name of Jim Thorpe, an Olympic medalist.[33] Howard Eby and Lauren Asplund claim to have invented the word as a joke in 1964, combining octo with the syllable therp which, because of the "th" digraph, was hard to pronounce in different languages.[34] The Merriam-Webster New Book of Word Histories, 1991, has a long article that is consistent with Doug Kerr's essay, which says "octotherp" was the original spelling, and that the word arose in the 1960s among telephone engineers as a joke. Other hypotheses for the origin of the word include the last name of James Oglethorpe[35] or using the Old English word for village, thorp, because the symbol looks like a village surrounded by eight fields.[36] [37] The word was popularized within and outside Bell Labs.[38] The first appearance of "octothorp" in a US patent is in a 1973 filing. This patent also refers to the six-pointed asterisk (✻) used on telephone buttons as a "sextile".[39] Sharp Use of the name "sharp" is due to the symbol's resemblance to . The same derivation is seen in the name of the Microsoft programming languages C#, J# and F#. Microsoft says that the name C# is pronounced 'see sharp'."[40] According to the ECMA-334 C# Language Specification, the name of the language is written "C#" (" (U+0043) followed by the # (U+0023)") and pronounced "C Sharp".[41] Square On telephones, the International Telecommunication Union specification ITU-T E.161 3.2.2 states: "The symbol may be referred to as the square or the most commonly used equivalent term in other languages."[42] Formally, this is not a number sign but rather another character, . The real or virtual keypads on almost all modern telephones use the simple instead, as does most documentation.Other Names that may be seen include:[43] crosshatch, crunch, fence, flash, garden fence, garden gate, gate, grid, hak, mesh, oof, pig-pen, punch mark, rake, scratch, scratch mark, tic-tac-toe, and unequal. UsageWhen prefixes a number, it is read as "number". "A #2 pencil", for example, indicates "a number-two pencil". The abbreviations 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.[44] 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.[45] 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). Mathematics
|S| S=\{s1,s2,s3,...,sn\} si \#S=n=|S|. a\midb
Computing
Other uses
UnicodeThe number sign was assigned code 35 (hex 0x23) in ASCII where it was inherited by many character sets. In EBCDIC it is often at 0x7B or 0xEC. Unicode characters with "number sign" in their names:
Additionally, a Unicode named sequence is defined for the grapheme cluster (#️⃣).[62] On keyboardsOn the standard US keyboard layout, the symbol is . 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, on Mac OS with, and on Linux with . See also
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