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Echo (computing)
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<h2 id="terminological-confusion-echo-is-not-duplex">Terminological confusion: echo is not duplex</h2> <p>A displayed 'echo' is independent of 'duplex' (or any) telecommunications transmission protocol. Probably from technical ignorance, "half-duplex" and "full-duplex" are used as slang for 'local echo' (a/k/a echo on) and 'remote echo', respectively, as typically they accompany one another. Strictly incorrect, this causes confusion (see <a href="/facts/Duplex_(telecommunications)/LCULeVxr">duplex</a>). Typically 'local echo' accompanies half-duplex transmission, which effectively doubles channel bandwidth by not repeating (echoing) data back from its destination (remote), as is reserved-for with 'full duplex' (which has only half of the bandwidth of 'half duplex'). Half-duplex can be set to 'echo off' for no echo at all.<a class="footnote-ref" id="fnref:8" href="#fn:8"><sup>8</sup></a><a class="footnote-ref" id="fnref:9" href="#fn:9"><sup>9</sup></a> </p><p>One example of 'local echo' used together with 'remote echo' (requires full-duplex) is for error checking pairs of data characters or chunks (echoplex) ensuring their duplicity (or else its just an extraneous annoyance).<a class="footnote-ref" id="fnref:10" href="#fn:10"><sup>10</sup></a><a class="footnote-ref" id="fnref:11" href="#fn:11"><sup>11</sup></a> </p><p>Similarly, for another example, in the case of the <a href="/facts/TELNET/hxT0e85h">TELNET</a> communications protocol a local echo protocol operates on top of a full-duplex underlying protocol. The <a href="/facts/Transmission_Control_Protocol/WW4sPrt9">TCP</a> connection over which the TELNET protocol is layered provides a full-duplex connection, with no echo, across which data may be sent in either direction simultaneously.<a class="footnote-ref" id="fnref:12" href="#fn:12"><sup>12</sup></a> Whereas the <i>Network Virtual Terminal</i> that the TELNET protocol itself incorporates is a half-duplex device with (by default) local echo.<a class="footnote-ref" id="fnref:13" href="#fn:13"><sup>13</sup></a><a class="footnote-ref" id="fnref:14" href="#fn:14"><sup>14</sup></a> </p> <h2 id="the-devices-that-echo-locally">The devices that echo locally</h2> <p><a href="/facts/Terminal_(telecommunication)/GTHNGWI5">Terminals</a> are one of the things that may perform echoing for a connection. Others include modems, some form of intervening communications processor, or even the host system itself.<a class="footnote-ref" id="fnref:15" href="#fn:15"><sup>15</sup></a> For several common computer <a href="/facts/Operating_system/8XTuvMh2">operating systems</a>, it is the host system itself that performs the echoing, if appropriate (which it isn't for, say, entry of a user password when a terminal first connects and a user is prompted to log in). On <a href="/facts/OpenVMS/rAnHAgpD">OpenVMS</a>, for example, echoing is performed as necessary by the host system. Similarly, on <a href="/facts/Unix-like/YAKrAxzd">Unix-like</a> systems, local echo is performed by the operating system kernel's <i>terminal device driver</i>, according to the state of a device control flag, maintained in software and alterable by applications programs via an <a href="/facts/Ioctl/119Wrsz9">ioctl()</a> system call.<a class="footnote-ref" id="fnref:16" href="#fn:16"><sup>16</sup></a><a class="footnote-ref" id="fnref:17" href="#fn:17"><sup>17</sup></a> The actual terminals and modems connected to such systems should have <i>their</i> local echo facilities switched off (so that they operate in <i>no echo</i> mode), lest passwords be locally echoed at password prompts, and all other input appear echoed twice. This is as true for <a href="/facts/Terminal_emulator/yNfevBJd">terminal emulator</a> programs, such as <a href="/facts/C-Kermit/NFqqhPMf">C-Kermit</a>, running on a computer as it is for real terminals.<a class="footnote-ref" id="fnref:18" href="#fn:18"><sup>18</sup></a><a class="footnote-ref" id="fnref:19" href="#fn:19"><sup>19</sup></a> </p> <h2 id="controlling-local-echo">Controlling local echo</h2> <h3>Terminal emulators</h3> <p>Most terminal emulator programs have the ability to perform echo locally (which sometimes they misname "half-duplex"):<a class="footnote-ref" id="fnref:20" href="#fn:20"><sup>20</sup></a> </p> <ul><li>In the C-Kermit terminal emulator program, local echo is controlled by the SET TERMINAL ECHO command, which can be either SET TERMINAL ECHO LOCAL (which enables local echoing within the terminal emulator program itself) or SET TERMINAL ECHO REMOTE (where disables local echoing, leaving that up to another device in the communications channel—be that the modem or the remote host system—to perform as appropriate).<a class="footnote-ref" id="fnref:21" href="#fn:21"><sup>21</sup></a></li> <li>In <a href="/facts/ProComm/N8DSGVxK">ProComm</a> it is the Alt+E combination, which is a hot key that may be used at any time to toggle local echo on and off.<a class="footnote-ref" id="fnref:22" href="#fn:22"><sup>22</sup></a></li> <li>In the Terminal program that came with <a href="/facts/Microsoft_Windows_3.1/zYnWyaC6">Microsoft Windows 3.1</a>, local echo is controlled by a checkbox in the "Terminal Preferences" dialogue box accessed from the menu of the terminal program's window.<a class="footnote-ref" id="fnref:23" href="#fn:23"><sup>23</sup></a><a class="footnote-ref" id="fnref:24" href="#fn:24"><sup>24</sup></a><a class="footnote-ref" id="fnref:25" href="#fn:25"><sup>25</sup></a></li></ul> <h3>Modems</h3> <p>The <a href="/facts/Hayes_command_set/jqgtsCtH">Hayes AT commands</a> that control local echo (in command mode) are E0 for off and E1 for on. For local echo (in data mode), the commands are F1 and F0 respectively. Note the reversal of the suffixed digits. Unlike the "E" commands, the "F" commands are not part of the EIA/TIA-602 standard.<a class="footnote-ref" id="fnref:26" href="#fn:26"><sup>26</sup></a><a class="footnote-ref" id="fnref:27" href="#fn:27"><sup>27</sup></a> </p> <h3>Host systems</h3> <p>Some host systems perform local echo themselves, in their device drivers and so forth. </p> <ul><li>In Unix and POSIX-compatible systems, local echo is a flag in the <a href="/facts/POSIX_terminal_interface/Y4qgsGD0">POSIX terminal interface</a>, settable programmatically with the tcsetattr() function.<a class="footnote-ref" id="fnref:28" href="#fn:28"><sup>28</sup></a><a class="footnote-ref" id="fnref:29" href="#fn:29"><sup>29</sup></a> The echoing is performed by the operating system's terminal device (in some way that is not specified by the POSIX standard). The standard utility program that alters this flag programmatically is the stty command, using which the flag may be altered from <a href="/facts/Shell_script/NE7YvsBD">shell scripts</a> or an interactive shell.<a class="footnote-ref" id="fnref:30" href="#fn:30"><sup>30</sup></a> The command to turn local echo (by the host system) on is stty echo and the command to turn it off is stty -echo.<a class="footnote-ref" id="fnref:31" href="#fn:31"><sup>31</sup></a><a class="footnote-ref" id="fnref:32" href="#fn:32"><sup>32</sup></a></li> <li>On OpenVMS systems, the operating system's terminal driver normally performs echoing.<a class="footnote-ref" id="fnref:33" href="#fn:33"><sup>33</sup></a> The <i>terminal characteristic</i> that controls whether it does this is the ECHO characteristic, settable with the DCL command SET TERMINAL /ECHO and unsettable with SET TERMINAL /NOECHO.<a class="footnote-ref" id="fnref:34" href="#fn:34"><sup>34</sup></a> <a class="footnote-ref" id="fnref:35" href="#fn:35"><sup>35</sup></a></li></ul> <h2 id="footnotes">Footnotes</h2> <h3>What supports what</h3> <h3>Sources used</h3> <ul><li>Bagad, V.S.; Dhotre, I.A. (2009). <i>Data Communication & Networking</i>. Technical Publications. <a href="/facts/ISBN_(identifier)/15AdSPa9">ISBN</a> 978-81-8431-759-6.</li> <li>Black, Uyless D. (1987). <a href="https://archive.org/details/datacommunicatio0000blac_w5w1"><i>Data communications and distributed networks</i></a> (2nd ed.). Prentice-Hall. <a href="/facts/ISBN_(identifier)/15AdSPa9">ISBN</a> 978-0-8359-1341-6.</li> <li>Bigelow, Stephen J. (2000). <a href="https://archive.org/details/pctechnicianstro0000bige"><i>PC Technician's Troubleshooting Pocket Reference</i></a> (2nd ed.). McGraw-Hill Professional. <a href="/facts/ISBN_(identifier)/15AdSPa9">ISBN</a> 978-0-07-212945-8.</li> <li>Cowart, Robert (1992). <a href="https://archive.org/details/masteringwindows00cowa"><i>Mastering Windows 3.1</i></a>. Sybex. <a href="/facts/ISBN_(identifier)/15AdSPa9">ISBN</a> 978-0-89588-842-6.</li> <li>Daintith, John (2004). "echo". <i>Oxford dictionary of computing</i> (5th ed.). Oxford University Press. <a href="/facts/ISBN_(identifier)/15AdSPa9">ISBN</a> 978-0-19-860877-6.</li> <li>Da Cruz, Frank; Gianone, Christine M. (1997). <i>Using C-Kermit: communication software</i> (2nd ed.). Digital Press. <a href="/facts/ISBN_(identifier)/15AdSPa9">ISBN</a> 978-1-55558-164-0.</li> <li>Duffy, Michael D. (2002). <i>Getting started with OpenVMS: a guide for new users</i>. Digital Press. <a href="/facts/ISBN_(identifier)/15AdSPa9">ISBN</a> 978-1-55558-279-1.</li> <li>Durda, Frank (2004). <a href="https://web.archive.org/web/20101124090434/http://nemesis.lonestar.org/reference/telecom/modems/at/plain-at.html">"Section 3: Unprefixed AT Commands"</a>. <i>The AT Command Set Reference</i>. Archived from <a href="http://nemesis.lonestar.org./reference/telecom/modems/at/plain-at.html">the original</a> on 2010-11-24. Retrieved 2011-01-23.</li> <li>Graf, Rudolf F. (1999). "echo". <i>Modern dictionary of electronics</i> (6th ed.). Newnes. <a href="/facts/ISBN_(identifier)/15AdSPa9">ISBN</a> 978-0-7506-9866-5.</li> <li>Hill Associates (2002). <a href="https://archive.org/details/telecommunicatio00hill"><i>Telecommunications: a beginner's guide</i></a>. Network professional's library. McGraw-Hill Professional. <a href="/facts/ISBN_(identifier)/15AdSPa9">ISBN</a> 978-0-07-219356-5.</li> <li><a href="https://web.archive.org/web/20110707211131/http://bandwidthco.com/whitepapers/netforensics/telnet/Telnet%20and%20the%20Telnet%20Protocol.pdf">"Telnet and the Telnet Protocol"</a> (PDF). <a href="/facts/IBM/QszA7nwd">IBM</a>. June 1995. Archived from <a href="http://bandwidthco.com./whitepapers/netforensics/telnet/Telnet%20and%20the%20Telnet%20Protocol.pdf">the original</a> (PDF) on 2011-07-07. Retrieved 2011-01-23.</li> <li>Jordan, Larry E.; Churchill, Bruce (1987). <i>Communications and networking for the IBM PC & compatibles</i> (2nd ed.). Brady. <a href="/facts/ISBN_(identifier)/15AdSPa9">ISBN</a> 978-0-89303-634-8.</li> <li>Leffler, Samuel J.; <a href="/facts/Marshall_Kirk_McKusick/NH1M5PrV">McKusick, Marshall Kirk</a>; Karels, Michael J.; <a href="/facts/John_Quarterman/olezNFQK">Quarterman, John S.</a> (1989). "Terminal Handling". <a href="https://archive.org/details/designimplementa0000unse"><i>The Design and implementation of the 4.3BSD UNIX operating system</i></a>. Addison-Wesley series in computer science. Addison-Wesley. <a href="/facts/ISBN_(identifier)/15AdSPa9">ISBN</a> 978-0-201-06196-3.</li> <li>Leisner, K. M.; Cook, David B. (1990). <i>VAX DCL programmer's reference VMS 5</i>. Van Nostrand Reinhold. <a href="/facts/ISBN_(identifier)/15AdSPa9">ISBN</a> 978-0-442-31834-5.</li> <li>Miller, David Donald (1992). <i>VAX/VMS: operating system concepts</i>. VAX-VMS Series. Digital Press. <a href="/facts/ISBN_(identifier)/15AdSPa9">ISBN</a> 978-1-55558-065-0.</li> <li><a href="/facts/Peter_Norton/KpEtRdIL">Norton, Peter</a>; Kent, Peter (1993). <i>Peter Norton's user's guide to Windows 3.1</i>. Bantam Books. <a href="/facts/ISBN_(identifier)/15AdSPa9">ISBN</a> 978-0-553-37148-2.</li> <li>Ramey, Chet, ed. (2009). <a href="http://tiswww.case.edu./php/chet/readline/readline.html#SEC43">"2.5 Readline Signal Handling"</a>. <i>GNU Readline Library</i>.</li> <li><a href="/facts/Jon_Postel/7FIv4teq">Postel, Jon</a>; Reynolds, J. (May 1983). <a href="http://tools.ietf.org/html/rfc0857#section-4">"Motivation for the Option"</a>. <i>RFC 0857: Telnet Echo Option</i>.</li> <li>Robbins, Kay A.; Robbins, Steven (2003). <a href="https://archive.org/details/unixsystemsprogr0000robb"><i>UNIX systems programming: communication, concurrency, and threads</i></a> (2nd ed.). Prentice Hall PTR. <a href="/facts/ISBN_(identifier)/15AdSPa9">ISBN</a> 978-0-13-042411-2.</li> <li>Rosch, Winn L. (1999). <a href="https://archive.org/details/winnlroschhardwa00rosc_1"><i>Winn L. Rosch hardware bible</i></a> (5th ed.). Que. <a href="/facts/ISBN_(identifier)/15AdSPa9">ISBN</a> 978-0-7897-1743-6.</li> <li>Sheldon, Thomas (1991). <i>Windows 3: the complete reference</i>. Osborne McGraw-Hill. <a href="/facts/ISBN_(identifier)/15AdSPa9">ISBN</a> 978-0-07-881679-6.</li> <li>Sobell, Mark G.; Seebach, Peter (2006). <i>A practical guide to Unix for Mac OS X users</i>. Prentice Hall PTR. <a href="/facts/ISBN_(identifier)/15AdSPa9">ISBN</a> 978-0-13-186333-0.</li> <li>Socolofsky, T.; Kale, C. (January 1991). <a href="http://tools.ietf.org/html/rfc1180#section-7">"Transmission Control Protocol"</a>. <i>RFC 1180: A TCP/IP Tutorial</i>. <a href="/facts/Doi_(identifier)/muM9Etpq">doi</a>:<a href="https://doi.org/10.17487%2FRFC1180">10.17487/RFC1180</a>.</li> <li>Weik, Martin H. (2000). <i>Computer Science and Communications Dictionary</i>. Vol. 1. Springer. <a href="/facts/ISBN_(identifier)/15AdSPa9">ISBN</a> 978-0-7923-8425-0. {{cite encyclopedia}}: Missing or empty |title= (help)</li> <li>Woggon, Michele (1995). <i>Telecommunications using ProComm & ProComm Plus made easy</i>. Prentice Hall. <a href="/facts/ISBN_(identifier)/15AdSPa9">ISBN</a> 978-0-13-148412-2.</li> <li>"local echo". <i>Advanced learner's dictionary of journalism</i>. Advanced Learner's Dictionary Series. Anmol Publications PVT LTD. 2000. <a href="/facts/ISBN_(identifier)/15AdSPa9">ISBN</a> 978-81-261-0469-7.</li></ul> <h2 id="references">References</h2> <ol> <li id="fn:1"><p>Graf 1999, p. 230. - Graf, Rudolf F. (1999). "echo". Modern dictionary of electronics (6th ed.). Newnes. ISBN 978-0-7506-9866-5. <a href="#fnref:1" class="footnote-back-ref">↩</a></p></li> <li id="fn:2"><p>Anmol 2000, p. 80. - "local echo". Advanced learner's dictionary of journalism. Advanced Learner's Dictionary Series. Anmol Publications PVT LTD. 2000. ISBN 978-81-261-0469-7. <a href="#fnref:2" class="footnote-back-ref">↩</a></p></li> <li id="fn:3"><p>Rosch 1999, p. 1161. - Rosch, Winn L. (1999). Winn L. Rosch hardware bible (5th ed.). Que. ISBN 978-0-7897-1743-6. <a href="https://archive.org/details/winnlroschhardwa00rosc_1" target="_blank">https://archive.org/details/winnlroschhardwa00rosc_1</a> <a href="#fnref:3" class="footnote-back-ref">↩</a></p></li> <li id="fn:4"><p>Weik 2000, "echo check" p. 478. - Weik, Martin H. (2000). Computer Science and Communications Dictionary. Vol. 1. Springer. ISBN 978-0-7923-8425-0. <a href="#fnref:4" class="footnote-back-ref">↩</a></p></li> <li id="fn:5"><p>Weik 2000, "echoplex" p.479. - Weik, Martin H. (2000). Computer Science and Communications Dictionary. Vol. 1. Springer. ISBN 978-0-7923-8425-0. <a href="#fnref:5" class="footnote-back-ref">↩</a></p></li> <li id="fn:6"><p>Jordan & Churchill 1987, p. 24. - Jordan, Larry E.; Churchill, Bruce (1987). Communications and networking for the IBM PC & compatibles (2nd ed.). Brady. ISBN 978-0-89303-634-8. <a href="#fnref:6" class="footnote-back-ref">↩</a></p></li> <li id="fn:7"><p>Hill Associates 2002, p. 341. - Hill Associates (2002). Telecommunications: a beginner's guide. Network professional's library. McGraw-Hill Professional. ISBN 978-0-07-219356-5. <a href="https://archive.org/details/telecommunicatio00hill" target="_blank">https://archive.org/details/telecommunicatio00hill</a> <a href="#fnref:7" class="footnote-back-ref">↩</a></p></li> <li id="fn:8"><p>Daintith 2004, p. 171. - Daintith, John (2004). "echo". Oxford dictionary of computing (5th ed.). Oxford University Press. ISBN 978-0-19-860877-6. <a href="#fnref:8" class="footnote-back-ref">↩</a></p></li> <li id="fn:9"><p>Jordan & Churchill 1987, p. 24. - Jordan, Larry E.; Churchill, Bruce (1987). Communications and networking for the IBM PC & compatibles (2nd ed.). Brady. ISBN 978-0-89303-634-8. <a href="#fnref:9" class="footnote-back-ref">↩</a></p></li> <li id="fn:10"><p>Bagad & Dhotre 2009, p. 9–4. - Bagad, V.S.; Dhotre, I.A. (2009). Data Communication & Networking. Technical Publications. ISBN 978-81-8431-759-6. <a href="#fnref:10" class="footnote-back-ref">↩</a></p></li> <li id="fn:11"><p>Black 1987, p. 203. - Black, Uyless D. (1987). Data communications and distributed networks (2nd ed.). Prentice-Hall. ISBN 978-0-8359-1341-6. <a href="https://archive.org/details/datacommunicatio0000blac_w5w1" target="_blank">https://archive.org/details/datacommunicatio0000blac_w5w1</a> <a href="#fnref:11" class="footnote-back-ref">↩</a></p></li> <li id="fn:12"><p>Socolofsky & Kale 1991, p. 24. - Socolofsky, T.; Kale, C. (January 1991). "Transmission Control Protocol". RFC 1180: A TCP/IP Tutorial. doi:10.17487/RFC1180. <a href="http://tools.ietf.org/html/rfc1180#section-7" target="_blank">http://tools.ietf.org/html/rfc1180#section-7</a> <a href="#fnref:12" class="footnote-back-ref">↩</a></p></li> <li id="fn:13"><p>IBM 1995, p. 2. - "Telnet and the Telnet Protocol" (PDF). IBM. June 1995. Archived from the original (PDF) on 2011-07-07. Retrieved 2011-01-23. <a href="https://web.archive.org/web/20110707211131/http://bandwidthco.com/whitepapers/netforensics/telnet/Telnet%20and%20the%20Telnet%20Protocol.pdf" target="_blank">https://web.archive.org/web/20110707211131/http://bandwidthco.com/whitepapers/netforensics/telnet/Telnet%20and%20the%20Telnet%20Protocol.pdf</a> <a href="#fnref:13" class="footnote-back-ref">↩</a></p></li> <li id="fn:14"><p>Postel & Reynolds 1983, p. 2. - Postel, Jon; Reynolds, J. (May 1983). "Motivation for the Option". RFC 0857: Telnet Echo Option. <a href="http://tools.ietf.org/html/rfc0857#section-4" target="_blank">http://tools.ietf.org/html/rfc0857#section-4</a> <a href="#fnref:14" class="footnote-back-ref">↩</a></p></li> <li id="fn:15"><p>Daintith 2004, p. 171. - Daintith, John (2004). "echo". Oxford dictionary of computing (5th ed.). Oxford University Press. ISBN 978-0-19-860877-6. <a href="#fnref:15" class="footnote-back-ref">↩</a></p></li> <li id="fn:16"><p>Duffy 2002, p. 43. - Duffy, Michael D. (2002). Getting started with OpenVMS: a guide for new users. Digital Press. ISBN 978-1-55558-279-1. <a href="#fnref:16" class="footnote-back-ref">↩</a></p></li> <li id="fn:17"><p>Leffler et al. 1989, p. 38,262,272. - Leffler, Samuel J.; McKusick, Marshall Kirk; Karels, Michael J.; Quarterman, John S. (1989). "Terminal Handling". The Design and implementation of the 4.3BSD UNIX operating system. Addison-Wesley series in computer science. Addison-Wesley. ISBN 978-0-201-06196-3. <a href="https://archive.org/details/designimplementa0000unse" target="_blank">https://archive.org/details/designimplementa0000unse</a> <a href="#fnref:17" class="footnote-back-ref">↩</a></p></li> <li id="fn:18"><p>Duffy 2002, p. 43. - Duffy, Michael D. (2002). Getting started with OpenVMS: a guide for new users. Digital Press. ISBN 978-1-55558-279-1. <a href="#fnref:18" class="footnote-back-ref">↩</a></p></li> <li id="fn:19"><p>Da Cruz & Gianone 1997, p. 158–159. - Da Cruz, Frank; Gianone, Christine M. (1997). Using C-Kermit: communication software (2nd ed.). Digital Press. ISBN 978-1-55558-164-0. <a href="#fnref:19" class="footnote-back-ref">↩</a></p></li> <li id="fn:20"><p>Bigelow 2000, p. 308. - Bigelow, Stephen J. (2000). PC Technician's Troubleshooting Pocket Reference (2nd ed.). McGraw-Hill Professional. ISBN 978-0-07-212945-8. <a href="https://archive.org/details/pctechnicianstro0000bige" target="_blank">https://archive.org/details/pctechnicianstro0000bige</a> <a href="#fnref:20" class="footnote-back-ref">↩</a></p></li> <li id="fn:21"><p>Da Cruz & Gianone 1997, p. 158–159. - Da Cruz, Frank; Gianone, Christine M. (1997). Using C-Kermit: communication software (2nd ed.). Digital Press. ISBN 978-1-55558-164-0. <a href="#fnref:21" class="footnote-back-ref">↩</a></p></li> <li id="fn:22"><p>Woggon 1995, p. 101. - Woggon, Michele (1995). Telecommunications using ProComm & ProComm Plus made easy. Prentice Hall. ISBN 978-0-13-148412-2. <a href="#fnref:22" class="footnote-back-ref">↩</a></p></li> <li id="fn:23"><p>Cowart 1992, p. 283. - Cowart, Robert (1992). Mastering Windows 3.1. Sybex. ISBN 978-0-89588-842-6. <a href="https://archive.org/details/masteringwindows00cowa" target="_blank">https://archive.org/details/masteringwindows00cowa</a> <a href="#fnref:23" class="footnote-back-ref">↩</a></p></li> <li id="fn:24"><p>Sheldon 1991, p. 678. - Sheldon, Thomas (1991). Windows 3: the complete reference. Osborne McGraw-Hill. ISBN 978-0-07-881679-6. <a href="#fnref:24" class="footnote-back-ref">↩</a></p></li> <li id="fn:25"><p>Norton & Kent 1993, p. 347. - Norton, Peter; Kent, Peter (1993). Peter Norton's user's guide to Windows 3.1. Bantam Books. ISBN 978-0-553-37148-2. <a href="#fnref:25" class="footnote-back-ref">↩</a></p></li> <li id="fn:26"><p>Bigelow 2000, p. 308. - Bigelow, Stephen J. (2000). PC Technician's Troubleshooting Pocket Reference (2nd ed.). McGraw-Hill Professional. ISBN 978-0-07-212945-8. <a href="https://archive.org/details/pctechnicianstro0000bige" target="_blank">https://archive.org/details/pctechnicianstro0000bige</a> <a href="#fnref:26" class="footnote-back-ref">↩</a></p></li> <li id="fn:27"><p>Durda 2004. - Durda, Frank (2004). "Section 3: Unprefixed AT Commands". The AT Command Set Reference. Archived from the original on 2010-11-24. Retrieved 2011-01-23. <a href="https://web.archive.org/web/20101124090434/http://nemesis.lonestar.org/reference/telecom/modems/at/plain-at.html" target="_blank">https://web.archive.org/web/20101124090434/http://nemesis.lonestar.org/reference/telecom/modems/at/plain-at.html</a> <a href="#fnref:27" class="footnote-back-ref">↩</a></p></li> <li id="fn:28"><p>Robbins & Robbins 2003, p. 204–205. - Robbins, Kay A.; Robbins, Steven (2003). UNIX systems programming: communication, concurrency, and threads (2nd ed.). Prentice Hall PTR. ISBN 978-0-13-042411-2. <a href="https://archive.org/details/unixsystemsprogr0000robb" target="_blank">https://archive.org/details/unixsystemsprogr0000robb</a> <a href="#fnref:28" class="footnote-back-ref">↩</a></p></li> <li id="fn:29"><p>In the older and superseded Seventh Edition Unix terminal interface, BSD version 4 terminal interface, and System III/System V terminal interface, it was settable via the ioctl() system call.[24] <a href="/wiki/Seventh_Edition_Unix_terminal_interface" target="_blank">/wiki/Seventh_Edition_Unix_terminal_interface</a> <a href="#fnref:29" class="footnote-back-ref">↩</a></p></li> <li id="fn:30"><p>Robbins & Robbins 2003, p. 203. - Robbins, Kay A.; Robbins, Steven (2003). UNIX systems programming: communication, concurrency, and threads (2nd ed.). Prentice Hall PTR. ISBN 978-0-13-042411-2. <a href="https://archive.org/details/unixsystemsprogr0000robb" target="_blank">https://archive.org/details/unixsystemsprogr0000robb</a> <a href="#fnref:30" class="footnote-back-ref">↩</a></p></li> <li id="fn:31"><p>Sobell & Seebach 2006, p. 855. - Sobell, Mark G.; Seebach, Peter (2006). A practical guide to Unix for Mac OS X users. Prentice Hall PTR. ISBN 978-0-13-186333-0. <a href="#fnref:31" class="footnote-back-ref">↩</a></p></li> <li id="fn:32"><p>This may not seem to work if used interactively. It does work. It's just immediately overridden. Some shells, such as tcsh, reset the terminal modes, including turning local echo off, when they are about to prompt for input. They actually place the terminal into non-canonical mode with local echo off, and handle echoing themselves, restoring the prior terminal attributes when the input line has been read. Any shell or other program that uses GNU readline also exhibits this interaction with stty -echo.[27][28] <a href="/wiki/Tcsh" target="_blank">/wiki/Tcsh</a> <a href="#fnref:32" class="footnote-back-ref">↩</a></p></li> <li id="fn:33"><p>Miller 1992, p. 30. - Miller, David Donald (1992). VAX/VMS: operating system concepts. VAX-VMS Series. Digital Press. ISBN 978-1-55558-065-0. <a href="#fnref:33" class="footnote-back-ref">↩</a></p></li> <li id="fn:34"><p>Leisner & Cook 1990, p. 136,158. - Leisner, K. M.; Cook, David B. (1990). VAX DCL programmer's reference VMS 5. Van Nostrand Reinhold. ISBN 978-0-442-31834-5. <a href="#fnref:34" class="footnote-back-ref">↩</a></p></li> <li id="fn:35"><p>Note that this is not the same as the LOCAL_ECHO terminal characteristic, settable with the DCL command SET TERMINAL /LOCAL_ECHO and unsettable with SET TERMINAL /NOLOCAL_ECHO. That characteristic controls whether the terminal itself performs local echo.[14][30] <a href="#fnref:35" class="footnote-back-ref">↩</a></p></li> </ol>