X.PC is a deprecated communications protocol developed by

McDonnell-Douglas McDonnell Douglas was a major United States, American Aerospace manufacturer, aerospace manufacturing corporation and defense contractor, formed by the merger of McDonnell Aircraft and the Douglas Aircraft Company in 1967. Between then and its o ...

for connecting a

personal computer A personal computer (PC) is a multi-purpose microcomputer whose size, capabilities, and price make it feasible for individual use. Personal computers are intended to be operated directly by an end user, rather than by a computer expert or tec ...

to its

Tymnet Tymnet was an international data communications network headquartered in Cupertino, California that used virtual call packet-switched technology and X.25, SNA/ SDLC, BSC and Async interfaces to connect host computers (servers) at thousands of lar ...

packet-switched In telecommunications, packet switching is a method of grouping data into '' packets'' that are transmitted over a digital network. Packets are made of a header and a payload. Data in the header is used by networking hardware to direct the pac ...

public data

telecommunications network A telecommunications network is a group of nodes interconnected by telecommunications links that are used to exchange messages between the nodes. The links may use a variety of technologies based on the methodologies of circuit switching, message ...

. It is a subset of

X.25 X.25 is an ITU-T standard protocol suite for packet-switched data communication in wide area networks (WAN). It was originally defined by the International Telegraph and Telephone Consultative Committee (CCITT, now ITU-T) in a series of drafts ...

, a

CCITT The ITU Telecommunication Standardization Sector (ITU-T) is one of the three sectors (divisions or units) of the International Telecommunication Union (ITU). It is responsible for coordinating standards for telecommunications and Information Commu ...

standard for packet-switched networks. It is a

full-duplex A duplex communication system is a point-to-point system composed of two or more connected parties or devices that can communicate with one another in both directions. Duplex systems are employed in many communications networks, either to allow ...

, asynchronous and error-correcting

network protocol A communication protocol is a system of rules that allows two or more entities of a communications system to transmit information via any kind of variation of a physical quantity. The protocol defines the rules, syntax, semantics and synchroniza ...

that supports up to 15 simultaneous channels. It maintains automatic error correction during any communications session between two or more computers. X.PC was originally developed to enable connections up to 9600

baud In telecommunication and electronics, baud (; symbol: Bd) is a common unit of measurement of symbol rate, which is one of the components that determine the speed of communication over a data channel. It is the unit for symbol rate or modulatio ...

. Unlike MNP, a competing standard proposed by

Microcom Microcom, Inc., was a major modem vendor during the 1980s, although never as popular as the "big three", Hayes, U.S. Robotics (USR) and Telebit. Nevertheless, Microcom holds an important place in modem history for introducing the MNP error-cor ...

, X.PC was placed in the

public domain The public domain (PD) consists of all the creative work A creative work is a manifestation of creative effort including fine artwork (sculpture, paintings, drawing, sketching, performance art), dance, writing (literature), filmmaking, ...

for royalty-free usage. MNP, on the other hand, initially required a $2,500 licensing fee. Microcom battled X.PC for acceptance in the marketplace, and eventually released MNP 1 through 3 into the public domain to compete."MNP vs. X.PC. Will either triumph?"
''Network World'', 27 January 1986, p. 51 At the time, several modem manufacturers supported MNP in their products, Microcom and Racal-Vadic being major examples. Several companies announced support for X.PC, including Hayes, but none of the companies announcing support offered it in their modems. X.PC quickly disappeared, and Microcom would go on to release MNP 4 and 5 into the public domain as well.

References

External links

*http://www.mactech.com/articles/mactech/Vol.02/02.01/ProtocolStandards/ Network protocols X.25 {{telecom-stub