LANs connect computers and other devices such as printers in a limited physical area, such as an office. LANs are connected by permanent cables that allow rapid data transfer. A LAN will generally comprise several personal computers, shared peripheral devices such as printers and scanners, and a central file server with high-capacity disk storage. A LAN requires special operating system software to allow the various devices connected to the LAN to communicate with each other. In addition to the benefits derived from users sharing common data and programs, use of LANs allows systems administrators to impose standards on users and to ensure data is systematically backed up.
WANs can allow geographically dispersed computers to communicate with each and to share data.
For example, and EMB with several different offices, each with its own LAN, can have an EMB-wide WAN, allowing data to be shared across the organisation. WANs can be used to link computers from anywhere in the world, with access to appropriate telecommunications. WANs can be linked by cables or optical fibres, or by microwave links or radio links, using ground-based or satellite transmitters. WANs tend to be organisation-specific, allowing an organisation to connect all its employees into one network regardless of their physical locations. The largest WAN is the internet , a collection of networks linking millions of computer users around the world.