Editing Barcode (section)

{{short description|Optical machine-readable representation of data}}
{{for-multi|the taxonomic method|DNA barcoding|a code of conduct for barristers|Legal ethics}}
{{Use dmy dates|date=October 2024}} 
[[File:UPC-A-036000291452.svg|thumb|A [[Universal Product Code|UPC-A]] barcode]]
A '''barcode''' or '''bar code''' is a method of representing data in a visual, [[Machine-readable data|machine-readable form]]. Initially, barcodes represented data by varying the widths, spacings and sizes of parallel lines. These barcodes, now commonly referred to as linear or one-dimensional (1D), can be scanned by special [[optical scanner]]s, called [[barcode reader]]s, of which there are several types.

Later, two-dimensional (2D) variants were developed, using rectangles, dots, [[hexagon]]s and other patterns, called ''2D barcodes'' or ''matrix codes'', although they do not use bars as such. Both can be read using purpose-built 2D optical scanners, which exist in a few different forms<!-- including handled pistol-grip and stationary-->. Matrix codes can also be read by a digital camera connected to a microcomputer running software that takes a photographic image of the barcode and analyzes the image to deconstruct and decode the code. A [[mobile device]] with a built-in camera, such as a [[smartphone]], can function as the latter type of barcode reader using specialized [[application software]] and is suitable for both 1D and 2D codes.

[[File:Barcodes on British Railways rolling stock in 1962 (Modern Railways Dec 1962) 000130.jpg|thumb|Barcoded rolling stock in the UK, 1962]]
The barcode was invented by [[Norman Joseph Woodland]] and [[Bernard Silver]] and patented in the US in 1952.<ref name="patent">{{cite patent |country=US |number=2612994 |status=patent}}</ref> The invention was based on [[Morse code]]<ref>{{Cite web|url=https://www.stuffyoushouldknow.com/podcasts/how-barcodes-work.htm|title=How Barcodes Work|date=4 June 2019|website=Stuff You Should Know|language=en|access-date=5 June 2019|archive-date=5 June 2019|archive-url=https://web.archive.org/web/20190605080136/https://www.stuffyoushouldknow.com/podcasts/how-barcodes-work.htm|url-status=dead}}</ref> that was extended to thin and thick bars. However, it took over twenty years before this invention became commercially successful. UK magazine ''[[Modern Railways]]'' December 1962 pages 387–389 record how [[British Railways]] had already perfected a barcode-reading system capable of correctly reading rolling stock travelling at {{cvt|100|mph|km/h}} with no mistakes. An early use of one type of barcode in an industrial context was sponsored by the [[Association of American Railroads]] in the late 1960s. Developed by [[GTE|General Telephone and Electronics]] (GTE) and called [[KarTrak ACI]] (Automatic Car Identification), this scheme involved placing colored stripes in various combinations on steel plates which were affixed to the sides of railroad rolling stock. Two plates were used per car, one on each side, with the arrangement of the colored stripes encoding information such as ownership, type of equipment, and identification number.<ref name="Cranstone">{{cite web|url=http://www.nakina.net/other/aci/aci.html|title=A guide to ACI (Automatic Car Identification)/KarTrak|last=Cranstone|first=Ian|work=Canadian Freight Cars A resource page for the Canadian Freight Car Enthusiast|access-date=26 May 2013|archive-date=27 August 2011|archive-url=https://web.archive.org/web/20110827124711/http://www.nakina.net/other/aci/aci.html|url-status=live}}</ref> The plates were read by a trackside scanner located, for instance, at the entrance to a classification yard, while the car was moving past.<ref name="Keyes">{{cite web|last=Keyes|first=John|date=22 August 2003|title=KarTrak|url=http://johnkeyes.com/2003/08/kartrak|url-status=dead|archive-url=https://web.archive.org/web/20140310153027/http://johnkeyes.com/2003/08/kartrak|archive-date=10 March 2014|access-date=26 May 2013|work=John Keyes Boston photoblogger. Images from Boston, New England, and beyond.|publisher=John Keyes}}</ref> The project was abandoned after about ten years because the system proved unreliable after long-term use.<ref name="Cranstone" />

Barcodes became commercially successful when they were used to automate supermarket checkout systems, a task for which they have become almost universal. The Uniform Grocery Product Code Council had chosen, in 1973, the barcode design developed by [[George Laurer]]. Laurer's barcode, with vertical bars, printed better than the circular barcode developed by Woodland and Silver.<ref name=RobertsNYT>{{cite news |last1=Roberts |first1=Sam |title=George Laurer, Who Developed the Bar Code, Is Dead at 94 |url=https://www.nytimes.com/2019/12/11/technology/george-laurer-dead.html |access-date=13 December 2019 |work=[[The New York Times]] |date=11 December 2019 |archive-date=22 June 2020 |archive-url=https://web.archive.org/web/20200622055851/https://www.nytimes.com/2019/12/11/technology/george-laurer-dead.html?searchResultPosition=1 |url-status=live }}</ref> Their use has spread to many other tasks that are generically referred to as [[automatic identification and data capture]] (AIDC). The first successful system using barcodes was in the UK supermarket group [[Sainsbury's]] in 1972 using shelf-mounted barcodes which were developed by [[Plessey]].<ref name=":1">{{Cite journal |last=Brown |first=Derrick |date=Spring 2023 |title=The Birth of the Barcode |url=https://www.computerconservationsociety.org/resurrection/res101.htm#g |journal=The Journal of the [[Computer Conservation Society]] |issue=101 |issn=0958-7403}}</ref><ref>{{Cite web |last=Brown |first=Derrick |date=20 March 2023 |title=The Birth of the Barcode |url=https://www.bcs.org/articles-opinion-and-research/the-birth-of-the-barcode/ |url-status=live |archive-url=https://web.archive.org/web/20240806235748/https://www.bcs.org/articles-opinion-and-research/the-birth-of-the-barcode/ |archive-date=6 August 2024 |access-date=6 August 2024 |website=[[British Computer Society]]}}</ref> In June 1974, [[Marsh Supermarkets|Marsh supermarket]] in [[Troy, Ohio]] used a scanner made by [[PSC Inc.|Photographic Sciences Corporation]] to scan the [[Universal Product Code]] (UPC) barcode on a pack of [[Wrigley Company|Wrigley's]] chewing gum.<ref>{{cite news |last=Fox |first=Margalit |url=https://www.nytimes.com/2011/06/16/business/16haberman.html |title=Alan Haberman, Who Ushered in the Bar Code, Dies at 81 |work=[[The New York Times]] |date=15 June 2011 |access-date=24 February 2017 |archive-date=24 June 2017 |archive-url=https://web.archive.org/web/20170624163459/http://www.nytimes.com/2011/06/16/business/16haberman.html?_r=1&hp&gwh=7657EAA31B3069C9E728CC93FD2695E8 |url-status=live }}</ref>{{R|"RobertsNYT"}} [[QR code]]s, a specific type of 2D barcode, rose in popularity in the second decade of the 2000s due to the growth in smartphone ownership.<ref>{{cite news|title=Why QR codes are on the rise|url=https://www.economist.com/blogs/economist-explains/2017/11/economist-explains-0|author=G. F.|newspaper=The Economist|access-date=5 February 2018|language=en|date=2 November 2017|archive-date=5 February 2018|archive-url=https://web.archive.org/web/20180205184837/https://www.economist.com/blogs/economist-explains/2017/11/economist-explains-0|url-status=live}}</ref>

Other systems have made inroads in the [[automatic identification and data capture|AIDC]] market, but the simplicity, universality and low cost of barcodes has limited the role of these other systems, particularly before technologies such as [[radio-frequency identification]] (RFID) became available after 2023.