to protect the users' connections against failures within a network, power in a small desktop device. Users who required pure comput- be they the multiplexer itself or the network links. The techniques ing power, but not necessarily access to remote information, include channel re-routeing (many channels from a failed link to a benefited directly from this migration to PCs. Development of Local Area Networks (LANs) 56/7 PCs were also purchased in an effort to improve productivity by for interconnecting PCs. In addition, many LANs also connect automating manual processes, such as word processing, filing and mainframe and mini computer systems. accounting. At this point in time, the vast majority of PCs were installed as 56.4.3 LAN applications stand alone devices. That is to say, they were not attached to any other devices, except perhaps a printer. External communications, Local Area Networks can be utilised to provide any or all of the such as to other PCs within the same work area did not exist. following facilities (see Figure 56.9): However, as the computing power of the PC increased, and the need to make use of, and share the information on PCs also increased The interconnection of all computers, terminals, PCs and other connectivity, or networking, became a necessity. workstations within a department or building. 2. The effective communication between all devices attached to 56.4.2 Evolution of Local Area Networks the network, regardless of their vendor. 3. The sharing of expensive peripheral resources attached to the network such as disks, printers and plotters, central processors, The requirement for computer connectivity led to the development and databases. of the modern day Local Area Network (LAN). 4. The standardisation of wiring, hardware and software required The first LANs to appear on the market in the early 1980s were for communication and applications. represented by many different proprietary networking schemes 5. The establishment of a foundation for continued growth and the from a multitude 