DOS is a type of operating system known as a Line Interface. It is very different to what you might be used to using Windows or a Mac, which use GUIs (goo-ies), or Graphical Interfaces. Windows XP is a GUI and makes use of Windows, Icons, and Pointers (WIMP interface) to allow a user to interact with the computer. This type of interface is fairly easy to pick up quickly. Command Line Interfaces do not use a WIMP interface. They use commands like CD, DIR, COPY and so on. You have to learn all the commands like you would learn a foreign language and this takes a lot more time a GUI. However, it is very because you can up the commands to make the computer do very complex things, like you can put words together to make very complex sentences. This is why CLIs are very often used by Network to run networks. Because CLIs have a much less complex interface than a GUI, they need a amount of RAM to run and can therefore be run on even the oldest computer! One main drawback of CLIs, however, is that they don't use a environment. You can only open and run application at a time. In Windows, you can have many applications open at the same time and they can all run () together at the same time.