Editing Digital data (section)

== Symbol to digital conversion ==
{{original research|section|date=August 2016}}
Since symbols (for example, [[alphanumeric]] [[Character (computing)|characters]]) are not continuous, representing symbols digitally is rather simpler than conversion of continuous or analog information to digital. Instead of [[sampling (signal processing)|sampling]] and [[quantization (signal processing)|quantization]] as in [[analog-to-digital conversion]], such techniques as [[polling (computer science)|polling]] and [[Character encoding|encoding]] are used.

A symbol input device usually consists of a group of switches that are polled at regular intervals to see which switches are switched. Data will be lost if, within a single polling interval, two switches are pressed, or a switch is pressed, released, and pressed again. This polling can be done by a specialized processor in the device to prevent burdening the main [[Central processing unit|CPU]].<ref>{{Cite book |last1=Heinrich |first1=Lutz J. |url=https://books.google.com/books?id=Uq4FCgAAQBAJ&dq=Digitale+Daten+lexikon&pg=PA198 |title=Wirtschaftsinformatik-Lexikon |last2=Heinzl |first2=Armin |last3=Roithmayr |first3=Friedrich |date=2014-08-29 |publisher=Walter de Gruyter GmbH & Co KG |isbn=978-3-486-81590-0 |language=de}}</ref> When a new symbol has been entered, the device typically sends an [[interrupt]], in a specialized format, so that the CPU can read it.

For devices with only a few switches (such as the buttons on a [[joystick]]), the status of each can be encoded as bits (usually 0 for released and 1 for pressed) in a single word. This is useful when combinations of key presses are meaningful, and is sometimes used for passing the status of modifier keys on a keyboard (such as shift and control). But it does not scale to support more keys than the number of bits in a single byte or word.

Devices with many switches (such as a [[computer keyboard]]) usually arrange these switches in a scan matrix, with the individual switches on the intersections of x and y lines. When a switch is pressed, it connects the corresponding x and y lines together. Polling (often called scanning in this case) is done by activating each x line in sequence and detecting which y lines then have a [[digital signal|signal]], thus which keys are pressed. When the keyboard processor detects that a key has changed state, it sends a signal to the CPU indicating the scan code of the key and its new state. The symbol is then [[Code|encoded]] or converted into a number based on the status of modifier keys and the desired [[character encoding]].

A custom [[Character encoding|encoding]] can be used for a specific application with no loss of data. However, using a standard encoding such as [[ASCII]] is problematic if a symbol such as 'ß' needs to be converted but is not in the standard.

It is estimated that in the year 1986, less than 1% of the world's technological capacity to store information was digital and in 2007 it was already 94%.<ref name="HilbertLopez2011">{{cite magazine |url=https://www.science.org/doi/10.1126/science.1200970 |title=The World's Technological Capacity to Store, Communicate, and Compute Information |author1=Martin Hilbert |author2=Priscila López |magazine=[[Science (journal)|Science]] |volume=332 |issue=6025 |pages=60–65 |date=10 February 2011 |doi=10.1126/science.1200970 |archive-url=https://web.archive.org/web/20110531133712/http://www.sciencemag.org/content/suppl/2011/02/08/science.1200970.DC1/Hilbert-SOM.pdf |archive-date=31 May 2011 |url-status=live}} Also {{cite magazine |url=https://www.science.org/doi/suppl/10.1126/science.1200970/suppl_file/hilbert-som.pdf |title=Supporting online material for The World's Technological Capacity to Store, Communicate, and Compute Information |magazine=[[Science (journal)|Science]] |doi=10.1126/science.1200970 |archive-url=https://web.archive.org/web/20110531133712/http://www.sciencemag.org/content/suppl/2011/02/08/science.1200970.DC1/Hilbert-SOM.pdf |archive-date=31 May 2011 |url-status=live}} Free access to the article through here: {{URL|https://www.martinhilbert.net/WorldInfoCapacity.html/}}</ref> The year 2002 is assumed to be the year when humankind was able to store more information in digital than in analog format (the "beginning of the [[digital age]]").<ref name="Hilbertvideo2011">{{Cite web |title=video animation on The World's Technological Capacity to Store, Communicate, and Compute Information from 1986 to 2010 | date=11 June 2011 |url=https://www.youtube.com/watch?v=iIKPjOuwqHo |via=YouTube |access-date=6 November 2013 |archive-date=21 February 2013 |archive-url=https://web.archive.org/web/20130221144621/https://www.youtube.com/watch?v=iIKPjOuwqHo |url-status=live }}</ref><ref name=":0" />