ARCNET

Attached Resource Computer NETwork (ARCNET or ARCnet) is a for local area networks. ARCNET was the first widely available networking system for microcomputers; it became popular in the 1980s for office automation tasks. It was later applied to embedded systems where certain features of the protocol are especially useful.

ARCNET was developed by principal development engineer John Murphy at Datapoint Corporation in 1976 under Victor Poor, and announced in 1977. It was originally developed to connect groups of their Datapoint 2200 terminals to talk to a shared 8" floppy disk system. As microcomputers took over from the Datapoint, ARCNET was re-purposed as LAN. It was the first loosely coupled LAN-based clustering solution, making no assumptions about the type of computers that would be connected. This was in contrast to contemporary larger and more expensive computer systems such as DECnet or SNA, where a homogeneous group of similar or proprietary computers were connected as a cluster.

The token-passing bus protocol of that I/O device-sharing network was subsequently applied to allowing processing nodes to communicate with each other for file-serving and computing scalability purposes. An application could be developed in DATABUS, Datapoint's proprietary COBOL-like language and deployed on a single computer with dumb terminals. When the number of users outgrew the capacity of the original computer, additional 'compute' resource computers could be attached via ARCNET, running the same applications and accessing the same data. If more storage was needed, additional disk resource computers could also be attached. This incremental approach broke new ground and by the end of the 1970s (before the first cassette-based IBM PC was announced in 1981) over ten thousand ARCNET LAN installations were in commercial use around the world, and Datapoint had become a Fortune 500 company. As microcomputers took over the industry, well-proven and reliable ARCNET was also offered as an inexpensive LAN for these machines.

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