View source for Kermit (protocol)

{{Short description|File transfer protocol}}
{{Use dmy dates|date=March 2021}}
{{Infobox networking protocol
|       title = Kermit
|        logo = 
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|    is stack = 
|     purpose = [[File transfer]]
|   developer = Columbia University
|        date = {{Start date and age| 1981 |  |  }}<!--Fill in: Year (4 digits), month and day (2 digits)-->
|    based on = 
|  influenced = 
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|       ports = 
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}}

'''Kermit''' is a [[computer file]] transfer and management [[Communication protocol|protocol]] and a set of communications software tools primarily used in the early years of personal computing in the 1980s. It provides a consistent approach to file transfer, [[terminal emulator|terminal emulation]], [[scripting language|script]] programming, and [[character set]] conversion across many different [[computer hardware]] and [[operating system]] platforms.

==Technical==
The Kermit protocol supports [[Text file|text]] and [[binary file]] transfers on both full-duplex and half-duplex 8-bit and 7-bit [[RS-232|serial]] connections in a system- and medium-independent fashion, and is implemented on hundreds of different computer and operating system platforms. On full-duplex connections, a [[sliding window protocol]] is used with selective retransmission which provides excellent performance and error recovery characteristics. On 7-bit connections, locking shifts provide efficient transfer of 8-bit data. When properly implemented, as in the [[Columbia University]] Kermit Software collection, its authors claim performance is equal to or better than other protocols such as [[ZMODEM]], [[YMODEM]], and [[XMODEM]], especially on poor connections.<ref>Some of the sentences in the Technical section are based on text copied, on 30 October 2004, from the [[Free On-line Dictionary of Computing]], which is licensed under the [[GFDL]].</ref> On connections over [[RS-232]] [[Statistical time-division multiplexing|Statistical Multiplexers]] where some [[ASCII#ASCII control characters|control characters]] cannot be transmitted,{{Citation needed|date=August 2011}} Kermit can be configured to work, unlike protocols like XMODEM that require the connection to be transparent (i.e. all 256 possible values of a byte to be transferable).

Kermit can be used as a means to [[Bootstrapping|bootstrap]] other software, even itself. To distribute Kermit through non [[8-bit clean]] networks Columbia developed '''.boo''', a [[binary-to-text encoding]] system similar to [[BinHex]]. For instance, [[IBM PC compatible]]s and [[Apple computer]]s with a [[Compatibility card|Compatibility Card]] installed can connect to otherwise incompatible systems such as a [[mainframe computer]] to receive [[MS-DOS]] Kermit in .boo format. Users can then [[type-in program|type in a "baby Kermit"]] in [[BASIC]] on their personal computers that downloads Kermit and converts it into binary.<ref name="dacruz19860320">{{cite mailing list | url=http://www.columbia.edu/kermit/ftp/e/mail.86a | title=Re: Printable Encodings for Binary Files | publisher=Kermit Project, Columbia University | mailing-list=Info-Kermit Digest | date=1986-03-20 | access-date=1 March 2016 | author=da Cruz, Frank}}</ref><ref name="fuller19891011">{{cite mailing list | url=http://www.columbia.edu/kermit/ftp/e/mail.89b | title=Kermit Bootstrapping | publisher=Kermit Project, Columbia University | mailing-list=Info-Kermit Digest | date=1989-10-11 | access-date=5 March 2016 |author1=Fuller, Bill |author2=da Cruz, Frank }}</ref>

Similarly, [[CP/M]] machines use many different [[floppy disk]] formats, which means that one machine often cannot read disks from another CP/M machine, and Kermit is used as part of a process to transfer applications and data between CP/M machines and other machines with different operating systems. The CP/M file-copy program [[Peripheral Interchange Program|PIP]] can usually access a computer's serial ([[RS-232]]) port, and if configured to use a very low [[baud]] rate (because it has no built-in error correction) can be used to transfer a small, simple version of Kermit from one machine to another over a [[null modem]] cable, or failing that, a very simple version of the Kermit protocol can be hand coded in binary in less than 2K using DDT, the CP/M Dynamic Debugging Tool. Once done, the simple version of Kermit can be used to download a fully functional version. That version can then be used to transfer any CP/M application or data.<ref>{{Cite web|first=C. |last=Gianone |title=CP/M-80 KERMIT VERSION 4.11 USER GUIDE|publisher=Columbia University Center for Computing Activities|location=New York|date=23 April 1991|url=http://www.z80.eu/downloads/cpkermit.txt}} See "Figure 1-1:  Bootstrap program for Kermit-80 and CP/M Version 2.2"</ref>

Newer versions of Kermit included [[scripting language]] and automation of commands.<ref>[http://www.columbia.edu/kermit/k95.html columbia.edu Kermit 95]</ref> The Kermit scripting language evolved from its [[TOPS-20]] EXEC-inspired command language<ref>{{cite web |title=C-Kermit / Kermit 95 Scripting Tutorial and Library|url=http://www.kermitproject.org/ckscripts.html#introduction}}</ref> and was influenced syntactically and semantically by [[ALGOL 60]], [[C (programming language)|C]], [[BLISS|BLISS-10]], [[PL/I]], [[SNOBOL]], and [[Lisp (programming language)|LISP]].<ref>{{cite web |title=C-Kermit / Kermit 95 Scripting Tutorial and Library |url=https://kermitproject.org/ckscripts.html#intro }}</ref>

The correctness of the Kermit protocol has been verified with formal methods.<ref>{{Cite book|title=Specification and validation methods|last=Huggins|first=James K.|publisher=Oxford University Press|year=1995|isbn=0-19-853854-5|editor-last=Börger|editor-first=Egon|location=New York|pages=247–293|chapter=Kermit: specification and verification|chapter-url=http://www.kermitproject.org/proof.pdf}}</ref>

==History==
In the late 1970s, most of Columbia University's [[mainframe computer]]s had &le;64 kilobytes of total memory to work with.  Kermit was developed at the university so students could move files between them and [[floppy disk]]s at various [[microcomputer]]s around campus,<ref name="kermit198406">{{cite news | url=https://archive.org/stream/byte-magazine-1984-06/1984_06_BYTE_09-06_Computers_and_Education#page/n251/mode/2up | title=Kermit: A File-Transfer Protocol for Universities / Part 1: Design Considerations and Specifications | work=BYTE | date=June 1984 | access-date=23 October 2013 |author1=da Cruz, Frank |author2=Catchings, Bill | pages=251}}</ref><ref name="kermit198407">{{cite news | url=https://archive.org/stream/byte-magazine-1984-07/1984_07_BYTE_09-07_Computers_and_Video#page/n141/mode/2up | title=Kermit: A File-Transfer Protocol for Universities / Part 2: States and Transitions, Heuristic Rules, and Examples | work=BYTE | date=July 1984 | access-date=23 October 2013 |author1=da Cruz, Frank |author2=Catchings, Bill | pages=141}}</ref>{{r|ISS}} such as [[IBM]] or [[Digital Equipment Corporation|DEC]] [[DECSYSTEM-20]] mainframes and [[Intertec Superbrain]]s running [[CP/M]]. IBM mainframes used an [[EBCDIC]] character set and CP/M and DEC machines used [[ASCII]], so conversion between the two character sets was one of the early functions built into Kermit.

The protocol was originally designed in 1981 by Frank da Cruz and Bill Catchings.<ref name="Bai2004">{{cite book|author=Ying Bai|title=The Windows Serial Port Programming Handbook|url=https://books.google.com/books?id=iJzje_1tJA4C&pg=PA65|date=19 November 2004|publisher=CRC Press|isbn=978-0-203-34196-4|page=65}}</ref><ref name="RawlingsRawlings1986">{{cite book|author1=Christopher J. Rawlings|author2=S. Rawlings|title=Software Directory for Molecular Biology|url=https://books.google.com/books?id=CDNdDwAAQBAJ&pg=PA20|date=11 November 1986|publisher=Macmillan International Higher Education|isbn=978-1-349-08234-6|pages=20}}</ref>{{Better source|date=November 2025}} The first file transfer with Kermit occurred in April 1981.

Columbia University coordinated development of versions of Kermit for many different computers at the university and elsewhere, and distributed the software for free; Kermit for the new [[IBM Personal Computer]] became especially popular. In 1986 the university founded the Kermit Project, which took over development and started charging fees for commercial use; the project was financially self-sufficient.<ref name="ISS"/> For non-commercial use, Columbia University stated that<ref name="doupnik19880111">{{cite mailing list | url=http://www.columbia.edu/kermit/ftp/e/mail.88a | title=Announcing MS-DOS Kermit 2.30 | publisher=Kermit Project, Columbia University | mailing-list=Info-Kermit Digest | date=1988-01-11 | access-date=3 March 2016 |author1=Doupnik, Joe |author2=da Cruz, Frank }}</ref>

{{Blockquote|Kermit is for everyone to use and share. Once you get it, feel free to pass it along to your friends and colleagues. Although it is copyrighted and not in the public domain, we only ask that you not attempt to sell it for profit, and that you use it only for peaceful and humane purposes.}}

By 1988 Kermit was available on more than 300 computers and operating systems.<ref name="dacruz19880729">{{cite mailing list | url=http://www.columbia.edu/kermit/ftp/e/mail.88b | title=Kermits Needed | publisher=Kermit Project, Columbia University | mailing-list=Info-Kermit Digest | date=1988-07-29 | access-date=3 March 2016 | author=da Cruz, Frank}}</ref> The protocol became a [[de facto]] data communications standard<ref name="good">{{Cite web|url=http://www.masternewmedia.org/2003/12/26/standards_do_we_really_need.htm|title=Standards: Do We Really Need Them?|last=Good|first=Robin|date=23 December 2003|work=masternewmedia.org|access-date=27 April 2009}}</ref> for transferring files between dissimilar computer systems, and by the early 1990s it could convert multilingual [[character encoding]]s. Kermit software has been used in many countries, for tasks ranging from simple student assignments to solving [[Software incompatibility|compatibility]] problems aboard the [[International Space Station]].<ref name="ISS">[http://www.spacedaily.com/news/iss-03zq.html ''International Space Station Incorporates Kermit''] (December 2003)</ref> It was ported to a wide variety of mainframe, [[minicomputer]] and microcomputer systems down to handhelds and electronic pocket calculators. Most versions had a user interface based on the original TOPS-20 Kermit. Later versions of some Kermit implementations also support network as well as [[serial port|serial]] connections.

Implementations that are presently supported include '''[[C (programming language)|C]]-Kermit''' (for [[Unix]] and [[OpenVMS]]) and '''Kermit 95''' (for versions of [[Microsoft Windows]] from [[Windows 95]] onwards and [[OS/2]]), but other versions remain available as well.

As of 1 July 2011, Columbia University ceased to host this project and released it as [[open source]]. In June 2011, the Kermit Project released a beta version of C-Kermit v9.0 under the [[BSD licenses#3-clause license ("BSD License 2.0", "Revised BSD License", "New BSD License", or "Modified BSD License")|Revised 3-Clause BSD License]].<ref>{{cite web | url=http://www.columbia.edu/kermit/ck90.html | publisher=Columbia University's Kermit Project | title=C-Kermit 9.0 Beta Test |date=21 June 2011 | access-date=22 June 2011}}</ref>

As well as the implementations developed and/or distributed by Columbia University, the Kermit protocol was implemented in a number of third-party communications software packages, among others [[ProComm]] and [[ProComm Plus]].<ref name="Woggon1995">{{cite book|author=Michele Woggon|title=Telecommunications Using ProComm & ProComm Plus Made Easy|date=1 January 1995|publisher=Prentice Hall|isbn=978-0-13-148412-2|pages=30–31}}</ref><ref name="BruceElliott1991">{{cite book|author1=Walter R. Bruce|author2=Alan C. Elliott|title=Using Procomm Plus|date=1 April 1991|publisher=Que Corp.|isbn=978-0-88022-704-9|pages=139–143}}</ref><ref name="Krause1991">{{cite book|author=Joanne Krause|title=ProComm Plus 2.0 at Work|year=1991|publisher=Addison-Wesley Longman, Incorporated|isbn=978-0-201-57789-1|pages=109, 205}}</ref><ref name="Wang1994">{{cite book|author=Wally Wang|title=ProComm plus 2 for Windows for dummies|url=https://books.google.com/books?id=MdLmJONA9goC|year=1994|publisher=IDG Books|page=127|isbn=9781568842196}}</ref><ref name="CallahanAnis1990">{{cite book|author1=Mike Callahan|author2=Nick Anis|title=Dr. File Finder's Guide to Shareware|year=1990|publisher=Osborne McGraw-Hill|isbn=978-0-07-881646-8|page=386}}</ref> The term "SuperKermit" was coined by third-party vendors to refer to higher speed Kermit implementations offering features such as full duplex operation,<ref>{{cite book|title=Dictionary of Computer and Internet Words: An A to Z Guide to Hardware, Software, and Cyberspace|url=https://archive.org/details/dictionaryofcomp00bost|url-access=registration|year=2001|publisher=Houghton Mifflin Harcourt|isbn=0-618-10137-3|page=[https://archive.org/details/dictionaryofcomp00bost/page/150 150]}}</ref> sliding windows,<ref name="Johnston1986">{{cite journal|last=Johnston|first=Christopher|date=28 October 1986|title=Kermit|url=https://books.google.com/books?id=MK_-L8Mr1u4C&pg=PA132|journal=PC Magazine|publisher=Ziff Davis, Inc.|volume=5|issue=18|page=132|issn=0888-8507}}</ref><ref name="CallahanAnis1990b">{{citation|author1=Mike Callahan|author2=Nick Anis|title=Dr. File Finder's Guide to Shareware|year=1990|publisher=Osborne McGraw-Hill|isbn=978-0-07-881646-8|page=235}}</ref><ref name="Fist2012">{{citation|author=S.A. Fist|title=The Informatics Handbook: A guide to multimedia communications and broadcasting|url=https://books.google.com/books?id=R0_xBwAAQBAJ&pg=PA372|date=6 December 2012|publisher=Springer Science & Business Media|isbn=978-1-4615-2093-1|page=372}}</ref><ref name="BlankenhornMaxwell1992">{{citation|author1=Dana Blankenhorn|author2=Kimberly Maxwell|title=Technology edge: a guide to field computing|year=1992|publisher=New Riders Publishing|isbn=978-1-56205-091-7|page=286}}</ref><ref name="Becker1991">{{cite book|author=Philip L. Becker|title=Introduction to PC communications|date=September 1991|publisher=Que|isbn=978-0-88022-747-6|page=69}}</ref><ref name="Glossbrenner1993">{{cite book|author=Alfred Glossbrenner|title=Power DOS!: learn to run your PC like a master|date=31 March 1993|publisher=Random House Information Group|isbn=978-0-679-73924-1|page=[https://archive.org/details/powerdoslearntor0000glos/page/368 368]|url=https://archive.org/details/powerdoslearntor0000glos/page/368}}</ref> and long packets; however, that term was deprecated by the original Kermit team at Columbia University, who saw these as simply features of the core Kermit protocol.<ref>{{Cite web|url=http://www.columbia.edu/kermit/faq-c-sup.html|title=Kermit FAQ - What Is SuperKermit?|website=www.columbia.edu|access-date=2019-08-16}}</ref>

==Naming and copyright==
Kermit was named after [[Kermit the Frog]] from [[The Muppets]], with permission from [[Henson Associates]].<ref name="aboutkermit">{{Cite web |last=da Cruz |first=Frank |date=2025-02-15 |title=About Kermit |url=https://www.kermitproject.org/kermit.html |access-date=2025-04-08 |website=The Kermit Project}}</ref> The program's [[icon (computing)|icon]] in the [[Apple Macintosh]] version was a depiction of Kermit the Frog. A [[backronym]] was created, perhaps to avoid trademark issues, [[PDP-10|'''''K'''L10'']] '''E'''rror-Free '''R'''eciprocal '''M'''icroprocessor '''I'''nterchange over '''T'''TY lines,<ref>{{cite web|title=Superbrain Video Computer System|url=https://www.staff.ncl.ac.uk/roger.broughton/museum/micros/sb.htm|website=www.staff.ncl.ac.uk|access-date=24 February 2017|archive-date=15 February 2017|archive-url=https://web.archive.org/web/20170215192857/https://www.staff.ncl.ac.uk/roger.broughton/museum/micros/sb.htm|url-status=dead}}</ref> but the developers stopped using the backronym after obtaining permission.<ref name="kermitname">{{Cite web |last=da Cruz |first=Frank |date=September 2011 |title=Kermit Software Source Code Archive |url=https://www.kermitproject.org/archive.html |access-date=2025-04-08 |website=Kermit Project}}</ref>

Kermit is an open protocol—anybody can base their own program on it, but some Kermit software and source code is copyright by Columbia University.<ref>{{Cite web |title=Kermit Software: Frequently Asked Questions |url=http://www.columbia.edu/kermit/faq.html#license |url-status=dead |archive-url=https://web.archive.org/web/20230523081033/http://www.columbia.edu/kermit/faq.html |archive-date=2023-05-23 |access-date= |website=Columbia University}}</ref><ref>The preceding sentence is based on text copied, on 30 October 2004, from the [[Free On-line Dictionary of Computing]], which is licensed under the [[GFDL]].</ref> The final license page said:<ref>{{Cite web |title=C-Kermit 8.0 - Interactive Communication, File Transfer, and Scripting across Serial Ports, Modems, Secure Telnet, Secure Shell (SSH), FTP and HTTP for Unix, VMS, QNX, ... |url=http://www.columbia.edu/kermit/ck80.html#license |url-status=dead |archive-url=https://web.archive.org/web/20230316142007/http://www.columbia.edu/kermit/ck80.html#license |archive-date=2023-03-16 |access-date= |website=Columbia University}}</ref>
{{blockquote|As of version 9.0 (starting with the first Beta test), C-Kermit has an Open Source license, the Revised 3-Clause BSD License. Everybody can use it as they wish for any purpose, including redistribution and resale. It may be included with any operating system where it works or can be made to work, including both free and commercial versions of Unix and Hewlett-Packard (formerly DEC) VMS (OpenVMS). Technical support will be available from Columbia University only through 30 June 2011.}}

==See also==
* [[IND$FILE]]
* [[BLAST (protocol)]]
* [[XMODEM]]
* [[YMODEM]]

==References==
{{Reflist}}

==Further reading==
* {{cite book |title=Kermit: A File Transfer Protocol |last=da Cruz |first=Frank |location=Bedford |publisher=[[Digital Press]] |year=1987 |isbn=0-932376-88-6 |oclc=751527576 |url-access=registration |url=https://archive.org/details/kermitfiletransf0000dacr }}
* {{cite book |url=http://www.computerhistory.org/collections/catalog/102746411 |title=Kermit oral history panel |date=6 April 2012 |publisher=[[Computer History Museum]] }}
* {{cite book |url=http://www.computerhistory.org/collections/catalog/102721894 |title=Frank da Cruz Kermit records |last=da Cruz |first=Frank |publisher=Computer History Museum}}
* {{cite interview |url=http://www.computerhistory.org/collections/catalog/102746462 |title=Doupnik, Joe oral history |last=Doupnik |first=Joe |interviewer=Alex Bochannek |date=13 July 2012 |website=Computer History Museum}}

==External links==
* {{Official website}}
* {{cite web |url=http://kermit.columbia.edu/archive.html |title=Kermit Software Archive |last=da Cruz |first=Frank |website=Columbia University IT}}

{{Modem file transfer protocols}}
{{Authority control}}

{{DEFAULTSORT:Kermit}}
[[Category:1981 software]]
[[Category:BBS file transfer protocols]]
[[Category:Communication software]]
[[Category:File transfer protocols]]
[[Category:Terminal emulators]]
[[Category:Columbia University]]