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Until the introduction of PC DOS in 1981, [[IBM]] had no influence in this because their 1970s operating systems used EBCDIC encoding instead of ASCII, and they were oriented toward punch-card input and line printer output on which the concept of "carriage return" was meaningless. IBM's PC DOS (also marketed as [[MS-DOS]] by Microsoft) inherited the convention by virtue of being loosely based on CP/M,<ref>{{cite web|url=http://dosmandrivel.blogspot.com/2007/08/is-dos-rip-off-of-cpm.html|title=Is DOS a Rip-Off of CP/M?|author=Tim Paterson|date=August 8, 2007|website=DosMan Drivel|author-link=Tim Paterson|access-date=April 19, 2018|archive-url=https://web.archive.org/web/20180420075137/http://dosmandrivel.blogspot.com/2007/08/is-dos-rip-off-of-cpm.html|archive-date=April 20, 2018|url-status=live}}</ref> and [[Windows]] in turn inherited it from MS-DOS.
Requiring two characters to mark the end of a line introduces unnecessary complexity and ambiguity as to how to interpret each character when encountered by itself. To simplify matters, [[plain text]] data streams, including files, on [[Multics]] used line feed (LF) alone as a line terminator.<ref>{{cite conference |url=http://www.multicians.org/jhs-jfo-terminals.pdf |title=Technical and human engineering problems in connecting terminals to a time-sharing system |author-last1=Ossanna |author-first1=J. F. |author-link1=Joe Ossanna |author-last2=Saltzer |author-first2=J. H. |author-link2=Jerry Saltzer |date=November 17–19, 1970 |publisher=[[AFIPS]] Press |book-title=Proceedings of the November 17–19, 1970, [[Fall Joint Computer Conference]] (FJCC) |pages=355–362 |quote=Using a "new-line" function (combined carriage-return and line-feed) is simpler for both man and machine than requiring both functions for starting a new line; the American National Standard X3.4-1968 permits the line-feed code to carry the new-line meaning. |access-date=January 29, 2013 |archive-url=https://web.archive.org/web/20120819085101/http://www.multicians.org/jhs-jfo-terminals.pdf |archive-date=August 19, 2012 |url-status=live }}</ref>{{rp|357}} The tty driver would handle the LF to CRLF conversion on output so files can be directly printed to terminal, and NL (newline)
Computers attached to the [[ARPANET]] included machines running operating systems such as TOPS-10 and [[TENEX (operating system)|TENEX]] using CR-LF line endings; machines running operating systems such as Multics using LF line endings; and machines running operating systems such as [[OS/360]] that represented lines as a character count followed by the characters of the line and which used EBCDIC rather than ASCII encoding. The [[Telnet]] protocol defined an ASCII "[[Network Virtual Terminal]]" (NVT), so that connections between hosts with different line-ending conventions and character sets could be supported by transmitting a standard text format over the network. Telnet used ASCII along with CR-LF line endings, and software using other conventions would translate between the local conventions and the NVT.<ref name="RFC-158">{{cite IETF |title=TELNET Protocol |rfc=158 |pages=4–5 |author-first=T. |author-last=O'Sullivan |date=1971-05-19 |publisher=[[Internet Engineering Task Force]] (IETF) |access-date=2013-01-28}}</ref> The [[File Transfer Protocol]] adopted the Telnet protocol, including use of the Network Virtual Terminal, for use when transmitting commands and transferring data in the default ASCII mode.<ref name="RFC-542">{{cite IETF |title=File Transfer Protocol |rfc=542 |author-first=Nancy J. |author-last=Neigus |date=1973-08-12 |publisher=[[Internet Engineering Task Force]] (IETF) |access-date=2013-01-28}}</ref><ref name="RFC-765">{{cite IETF |title=File Transfer Protocol |rfc=765 |author-first=Jon |author-last=Postel |author-link=Jon Postel |date=June 1980 |publisher=[[Internet Engineering Task Force]] (IETF) |access-date=2013-01-28}}</ref> This adds complexity to implementations of those protocols, and to other network protocols, such as those used for E-mail and the World Wide Web, on systems not using the NVT's CR-LF line-ending convention.<ref>{{cite web |url=https://www.mercurial-scm.org/wiki/EOLTranslationPlan |title=EOL translation plan for Mercurial |publisher=Mercurial |access-date=2017-06-24 |archive-url=https://web.archive.org/web/20160616235536/https://www.mercurial-scm.org/wiki/EOLTranslationPlan |archive-date=June 16, 2016 |url-status=live }}</ref><ref>{{cite web |title=Bare LFs in SMTP |url=http://cr.yp.to/docs/smtplf.html |author-first=Daniel J. |author-last=Bernstein |author-link=Daniel J. Bernstein |access-date=2013-01-28 |archive-url=https://web.archive.org/web/20111029013105/http://cr.yp.to/docs/smtplf.html |archive-date=October 29, 2011 |url-status=live }}</ref>
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