Getting Started Guide 143 you see an error message, because cd and CD are two different things. Likewise, if you name a file report.DOC as you save it in your Linux word processor, you must use the same name to retrieve it. If you look for report.doc or REPORT.DOC, the file will not appear to exist. Linux generally uses all lowercase for commands and filenames. Command line The command line refers to a character mode display where you can type in com- mands that are executed when you press Enter. Although the command line is a character mode interface (because you enter characters instead of clicking on graphical items such as menus), you can also use a command line within a graph- ical environment. For example, choose Utilities|Terminal in KDE to open a com- mand line window. The command line window uses your default shell (command interpreter) to decide how to act on the commands you enter. For Linux, the default shell is bash. The command line interface to Linux can be referred to by several names. Although these names have specific meanings, you can use them synonymously: • A terminal window, refers to any command line interface, including one working from a remote location via a serial or network connection. • A terminal emulator, refers to a terminal window type of connection, but normally within a graphical environment. The command line window emulators (imitates) a terminal window, even though it’s running graphi- cally. • The console, refers to the command line interface of the keyboard and screen connected directly to the Linux system. • An x-term window, refers to a terminal window within a graphical envi- ronment that is being run using the x-term program, which simply pro- vides a window for the terminal interface and command line.