Kermit (protocol)
Encyclopedia
Kermit is a computer file
transfer/management 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 emulation
, script
programming, and character set conversion across many different computer hardware
and OS
platforms.
and binary file
transfers on both full-duplex and half-duplex 8 bit and 7-bit 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, Columbia University's Kermit group claim performance is equal to or better than other protocols such as ZMODEM
, YMODEM
, and XMODEM
, especially on poor connections. On connections over RS-232
Statistical Multiplexers
where some control characters do not transmit, Kermit can be configured to work, unlike protocols like XMODEM that require all 256 bytes be transmitted.
or DEC
DECSYSTEM-20
mainframe computer
s and removable media
on microcomputer
s (initially 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.
Kermit can be used as a bootstrap. For example CP/M machines used many different floppy disk
formats, which meant that one machine could not normally read disks from another CP/M machine, and Kermit was used as part of a process to enable the transfer of applications and data between CP/M machines and other machines with different operating systems. PIP
with a very low baud
rate (because it had no built-in error correction) could 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 very simple version of the Kermit protocol could be hand coded in binary in less than 2K using DDT, the CP/M Dynamic Debugging Tool. Once that was done the simple version of Kermit could be used to download a fully functional version. That version could then be used to transfer any CP/M application or data.
The Kermit protocol evolved through the 1980s into a de facto
data communications standard for transferring files between dissimilar computer systems. Kermit software has been used for tasks ranging from simple student assignments to solving compatibility
problems aboard the International Space Station
. It was ported to a wide variety of mainframe, minicomputer
and microcomputer systems. Most versions had a user interface based on the original TOPS-20 Kermit. The MS-DOS
version of Kermit was developed in 1983. Later versions of some Kermit implementations also support network as well as serial
connections.
Implementations that are presently supported include 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.
Kermit was initially developed by and distributed for free by the Columbia University, until 1986 when Columbia founded the Kermit Project which took over development and started charging fees for commercial use. The project is self-sufficient.. As of July 1st 2011, the Columbia University ceases to host this project and releases it to open source.
In 2011-06-21, Columbia University's Kermit Project released a beta version of C-Kermit v9.0 under an Open Source
Revised 3-Clause BSD License
from The Muppets
. The program's icon
in the Apple Macintosh version was a depiction of Kermit the Frog. A backronym
was nevertheless created, perhaps to avoid trademark issues, KL10
Error-Free Reciprocal Microprocessor Interchange over TTY lines.
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. As of version 9.0 (starting with the first test release after Alpha.09), 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.
Computer file
A computer file is a block of arbitrary information, or resource for storing information, which is available to a computer program and is usually based on some kind of durable storage. A file is durable in the sense that it remains available for programs to use after the current program has finished...
transfer/management 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 emulation
Terminal emulator
A terminal emulator, terminal application, term, or tty for short, is a program that emulates a video terminal within some other display architecture....
, script
Scripting language
A scripting language, script language, or extension language is a programming language that allows control of one or more applications. "Scripts" are distinct from the core code of the application, as they are usually written in a different language and are often created or at least modified by the...
programming, and character set conversion across many different computer hardware
Computer hardware
Personal computer hardware are component devices which are typically installed into or peripheral to a computer case to create a personal computer upon which system software is installed including a firmware interface such as a BIOS and an operating system which supports application software that...
and OS
Operating system
An operating system is a set of programs that manage computer hardware resources and provide common services for application software. The operating system is the most important type of system software in a computer system...
platforms.
Technical
The Kermit protocol supports textText file
A text file is a kind of computer file that is structured as a sequence of lines of electronic text. A text file exists within a computer file system...
and binary file
Binary file
A binary file is a computer file which may contain any type of data, encoded in binary form for computer storage and processing purposes; for example, computer document files containing formatted text...
transfers on both full-duplex and half-duplex 8 bit and 7-bit serial
RS-232
In telecommunications, RS-232 is the traditional name for a series of standards for serial binary single-ended data and control signals connecting between a DTE and a DCE . It is commonly used in computer serial ports...
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
Sliding Window Protocol
A sliding window protocol is a feature of packet-based data transmission protocols. Sliding window protocols are used where reliable in-order delivery of packets is required, such as in the Data Link Layer as well as in the Transmission Control Protocol .Conceptually, each portion of the...
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
Columbia University
Columbia University in the City of New York is a private, Ivy League university in Manhattan, New York City. Columbia is the oldest institution of higher learning in the state of New York, the fifth oldest in the United States, and one of the country's nine Colonial Colleges founded before the...
Kermit Software collection, Columbia University's Kermit group claim performance is equal to or better than other protocols such as ZMODEM
ZMODEM
ZMODEM is a file transfer protocol developed by Chuck Forsberg in 1986, in a project funded by Telenet in order to improve file transfers on their X.25 network...
, YMODEM
YMODEM
YMODEM is a protocol for file transfer used between modems. YMODEM was developed by Chuck Forsberg as the successor to XMODEM and MODEM7, and was first implemented in his CP/M YAM program...
, and XMODEM
XMODEM
XMODEM is a simple file transfer protocol developed as a quick hack by Ward Christensen for use in his 1977 MODEM.ASM terminal program. XMODEM became extremely popular in the early bulletin board system market, largely because it was so simple to implement...
, especially on poor connections. On connections over RS-232
RS-232
In telecommunications, RS-232 is the traditional name for a series of standards for serial binary single-ended data and control signals connecting between a DTE and a DCE . It is commonly used in computer serial ports...
Statistical Multiplexers
Statistical multiplexing
Statistical multiplexing is a type of communication link sharing, very similar to dynamic bandwidth allocation . In statistical multiplexing, a communication channel is divided into an arbitrary number of variable bit-rate digital channels or data streams. The link sharing is adapted to the...
where some control characters do not transmit, Kermit can be configured to work, unlike protocols like XMODEM that require all 256 bytes be transmitted.
History
Kermit was developed at Columbia University in 1981 to allow students to transfer files between IBMIBM
International Business Machines Corporation or IBM is an American multinational technology and consulting corporation headquartered in Armonk, New York, United States. IBM manufactures and sells computer hardware and software, and it offers infrastructure, hosting and consulting services in areas...
or DEC
Digital Equipment Corporation
Digital Equipment Corporation was a major American company in the computer industry and a leading vendor of computer systems, software and peripherals from the 1960s to the 1990s...
DECSYSTEM-20
DECSYSTEM-20
The DECSYSTEM-20 was a 36-bit Digital Equipment Corporation PDP-10 mainframe computer running the TOPS-20 operating system.PDP-10 computers running the TOPS-10 operating system were labeled DECsystem-10 as a way of differentiating them from the PDP-11...
mainframe computer
Mainframe computer
Mainframes are powerful computers used primarily by corporate and governmental organizations for critical applications, bulk data processing such as census, industry and consumer statistics, enterprise resource planning, and financial transaction processing.The term originally referred to the...
s and removable media
Removable media
In computer storage, removable media refers to storage media which is designed to be removed from the computer without powering the computer off.Some types of removable media are designed to be read by removable readers and drives...
on microcomputer
Microcomputer
A microcomputer is a computer with a microprocessor as its central processing unit. They are physically small compared to mainframe and minicomputers...
s (initially Intertec Superbrain
Intertec Superbrain
The Intertec Superbrain was an all-in-one commercial microcomputer first sold by Intertec in 1979. The machine ran the operating system CP/M and was somewhat unusual in that it used dual Z80 CPUs, the second being used as a disk controller...
s running CP/M
CP/M
CP/M was a mass-market operating system created for Intel 8080/85 based microcomputers by Gary Kildall of Digital Research, Inc...
). IBM mainframes used an EBCDIC
EBCDIC
Extended Binary Coded Decimal Interchange Code is an 8-bit character encoding used mainly on IBM mainframe and IBM midrange computer operating systems....
character set and CP/M and DEC machines used ASCII
ASCII
The American Standard Code for Information Interchange is a character-encoding scheme based on the ordering of the English alphabet. ASCII codes represent text in computers, communications equipment, and other devices that use text...
, so conversion between the two character sets was one of the early functions built into Kermit.
Kermit can be used as a bootstrap. For example CP/M machines used many different floppy disk
Floppy disk
A floppy disk is a disk storage medium composed of a disk of thin and flexible magnetic storage medium, sealed in a rectangular plastic carrier lined with fabric that removes dust particles...
formats, which meant that one machine could not normally read disks from another CP/M machine, and Kermit was used as part of a process to enable the transfer of applications and data between CP/M machines and other machines with different operating systems. PIP
Peripheral Interchange Program
Peripheral Interchange Program was a utility to transfer files on and between devices on Digital Equipment Corporation's computers. It was first implemented on the PDP-6 architecture by Harrison "Dit" Morse early in the 1960s...
with a very low baud
Baud
In telecommunications and electronics, baud is synonymous to symbols per second or pulses per second. It is the unit of symbol rate, also known as baud rate or modulation rate; the number of distinct symbol changes made to the transmission medium per second in a digitally modulated signal or a...
rate (because it had no built-in error correction) could be used to transfer a small simple version of Kermit from one machine to another over a null modem
Null modem
Null modem is a communication method to connect two DTEs directly using an RS-232 serial cable. The name stems from the historical use of the RS-232 cable to connect two teleprinter devices to modems in order to communicate with one another; null modem communication was possible by instead using...
cable, or failing that, a very very simple version of the Kermit protocol could be hand coded in binary in less than 2K using DDT, the CP/M Dynamic Debugging Tool. Once that was done the simple version of Kermit could be used to download a fully functional version. That version could then be used to transfer any CP/M application or data.
The Kermit protocol evolved through the 1980s into a de facto
De facto
De facto is a Latin expression that means "concerning fact." In law, it often means "in practice but not necessarily ordained by law" or "in practice or actuality, but not officially established." It is commonly used in contrast to de jure when referring to matters of law, governance, or...
data communications standard for transferring files between dissimilar computer systems. Kermit software has been used for tasks ranging from simple student assignments to solving compatibility
Software incompatibility
Software incompatibility is a characteristic of software components or systems which cannot operate satisfactorily together on the same computer, or on different computers linked by a computer network. They may be components or systems which are intended to operate cooperatively or independently...
problems aboard the International Space Station
International Space Station
The International Space Station is a habitable, artificial satellite in low Earth orbit. The ISS follows the Salyut, Almaz, Cosmos, Skylab, and Mir space stations, as the 11th space station launched, not including the Genesis I and II prototypes...
. It was ported to a wide variety of mainframe, minicomputer
Minicomputer
A minicomputer is a class of multi-user computers that lies in the middle range of the computing spectrum, in between the largest multi-user systems and the smallest single-user systems...
and microcomputer systems. Most versions had a user interface based on the original TOPS-20 Kermit. The MS-DOS
MS-DOS
MS-DOS is an operating system for x86-based personal computers. It was the most commonly used member of the DOS family of operating systems, and was the main operating system for IBM PC compatible personal computers during the 1980s to the mid 1990s, until it was gradually superseded by operating...
version of Kermit was developed in 1983. Later versions of some Kermit implementations also support network as well as serial
Serial port
In computing, a serial port is a serial communication physical interface through which information transfers in or out one bit at a time...
connections.
Implementations that are presently supported include C
C (programming language)
C is a general-purpose computer programming language developed between 1969 and 1973 by Dennis Ritchie at the Bell Telephone Laboratories for use with the Unix operating system....
-Kermit (for Unix
Unix
Unix is a multitasking, multi-user computer operating system originally developed in 1969 by a group of AT&T employees at Bell Labs, including Ken Thompson, Dennis Ritchie, Brian Kernighan, Douglas McIlroy, and Joe Ossanna...
and OpenVMS
OpenVMS
OpenVMS , previously known as VAX-11/VMS, VAX/VMS or VMS, is a computer server operating system that runs on VAX, Alpha and Itanium-based families of computers. Contrary to what its name suggests, OpenVMS is not open source software; however, the source listings are available for purchase...
) and Kermit 95 (for versions of Microsoft Windows
Microsoft Windows
Microsoft Windows is a series of operating systems produced by Microsoft.Microsoft introduced an operating environment named Windows on November 20, 1985 as an add-on to MS-DOS in response to the growing interest in graphical user interfaces . Microsoft Windows came to dominate the world's personal...
from Windows 95
Windows 95
Windows 95 is a consumer-oriented graphical user interface-based operating system. It was released on August 24, 1995 by Microsoft, and was a significant progression from the company's previous Windows products...
onwards and OS/2
OS/2
OS/2 is a computer operating system, initially created by Microsoft and IBM, then later developed by IBM exclusively. The name stands for "Operating System/2," because it was introduced as part of the same generation change release as IBM's "Personal System/2 " line of second-generation personal...
), but other versions remain available as well.
Kermit was initially developed by and distributed for free by the Columbia University, until 1986 when Columbia founded the Kermit Project which took over development and started charging fees for commercial use. The project is self-sufficient.. As of July 1st 2011, the Columbia University ceases to host this project and releases it to open source.
In 2011-06-21, Columbia University's Kermit Project released a beta version of C-Kermit v9.0 under an Open Source
Open source
The term open source describes practices in production and development that promote access to the end product's source materials. Some consider open source a philosophy, others consider it a pragmatic methodology...
Revised 3-Clause BSD License
Naming and copyright
Kermit was named after Kermit the FrogKermit the Frog
Kermit the Frog is puppeteer Jim Henson's most famous Muppet creation, first introduced in 1955. He is the protagonist of many Muppet projects, most notably as the host of The Muppet Show, and has appeared in various sketches on Sesame Street, in commercials and in public service announcements over...
from The Muppets
The Muppets
The Muppets are a group of puppet characters created by Jim Henson starting in 1954–55. Although the term is often used to refer to any puppet that resembles the distinctive style of The Muppet Show, the term is both an informal name and legal trademark owned by the Walt Disney Company in reference...
. The program's icon
Icon (computing)
A computer icon is a pictogram displayed on a computer screen and used to navigate a computer system or mobile device. The icon itself is a small picture or symbol serving as a quick, intuitive representation of a software tool, function or a data file accessible on the system. It functions as an...
in the Apple Macintosh version was a depiction of Kermit the Frog. A backronym
Backronym
A backronym or bacronym is a phrase constructed purposely, such that an acronym can be formed to a specific desired word. Backronyms may be invented with serious or humorous intent, or may be a type of false or folk etymology....
was nevertheless created, perhaps to avoid trademark issues, KL10
PDP-10
The PDP-10 was a mainframe computer family manufactured by Digital Equipment Corporation from the late 1960s on; the name stands for "Programmed Data Processor model 10". The first model was delivered in 1966...
Error-Free Reciprocal Microprocessor Interchange over TTY lines.
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. As of version 9.0 (starting with the first test release after Alpha.09), 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.