There are two ways to interact with Unix and Unix programs: through a text-only interface, or via a windows interface --- the Unix windowing system is called X. Which mode of interaction you use depends upon how you are accessing to the network, the software on the machine you are sitting at, and how fast your connection to the network is. But even if you are running X, one of the first things you are likely to open is an “xterm” , a text-only command window. Unix users tend to launch programs from the text-only interface. If the program itself supports windows, mice, etc., then they can point and click to their heart's content.

In this section, we'll concentrate on access via ssh, an internet protocol for issuing interactive commands to remote machines. Window-based X access will be introduced later.

There is an older text-based protocol for giving commands to Unix called "telnet". telnet is still used for a variety of purposes, but has fallen out of favor because it sends everything (including your login name and password) in plain-text format, leaving you vulnerable to someone else on your network eavesdropping via "packet sniffers".

By contrast, ssh encrypts all your communications, so you are safe even if someone is eavedropping. As of Summer 2008, the ODU CS dept will no longer support telnet connections.