One of the most important X features is that windows can come either from programs running on another computer or from an operating system other than UNIX. So, if your favorite MS-DOS program doesn’t run under UNIX but has an X interface, you can run the program under MS-DOS and display its windows with X on your UNIX computer. Researchers can run graphical data analysis programs on supercomputers in other parts of the country and see the results in their offices. There’s much more than we could cover here. The O’Reilly & Associates book X Window System User’s Guide, Volume Three, OSF/Motif Edition has all the details.
Of all the windows on your screen, only one window receives the keystrokes you type. This window is usually highlighted in some way. By default in the mwm window manager, for instance, the frame of the window that receives your input is a darker shade of grey. In X jargon, choosing the window you type to is called “setting the input focus.” Most window managers can be configured to set the focus in one of the following two ways:
Point to the window and click a mouse button (usually the first button). You may need to click on the titlebar at the top of the window.
Simply move the pointer inside the window.
When you use mwm, any new windows will get the input focus automatically as they pop up.
One of the most important windows is an xterm window. xterm makes a terminal emulator window with a UNIX login session inside, ...