Many offices decide to network because they have more than one computer and want to share one broadband Internet connection.

There are side benefits as well, including file sharing, which includes pictures, music and more with all users on the network. Each user can share a single printer or multi function device like a fax / scanner on the network.

If the network has a  wireless  port, Desktop & Laptop computers can be set up where they're convenient  and not just where there's a wire. And laptop computer users are free to roam almost anywhere in, or around, the network — without losing their connection, utilizing all the network resources as they go...

To sum it up, a network is convenient & cost effective.