What is X Windows?

The X Window System is a network based graphical windowing system for workstations. It was developed by MIT and has been adopted as an industry standard.
X is supported by a consortium of industry leaders such as DEC, Sun, IBM, Hewlett-Packard and AT&T. They have united to direct, contribute and fund the continuing development of X.
Most UNIX machines include X as part of their operating system. If you have "windows" on your screen, chances are, you are using X, whether you are aware of it or not. It is simply "part of your environment".
The X Window System design is based upon the client-server model:
- Client: an application program which performs a specific task. For example, three common X clients (xclock, xcalc, xterm) appear below:
- Display Server: a program which acts as the intermediary between client programs and the machine hardware. Keeps track of all user and client input/output. Ordinarily, the display server program is started automatically for you or, you start it once, and then forget about it.
In conjunction with the X Window System, there is usually a Window Manager program which allows you to control certain X client parameters:
- size of client
- location on screen
- whether or not client is iconified
- termination of client
The topics of X Windows and window managers are very extensive. For more details, consult any of the many references available.

Getting Started Using X Windows

Three things must be done in order to use the X Window System:
1. Start the X display server
2. Start a window manager
3. Start the first instance of the xterm terminal emulator
Starting the X display server. This may vary depending upon your local system.
- Some systems will start the X server for you automatically and provide you with an initial login window. This is probably the case if you see a login screen that looks something like the one below:
- Other systems will start the X server for you automatically using something called xdm. This is probably the case if you see a login screen that looks something like the one below:
- Some systems require you to start the X server manually. This is usually done with the "xinit" command. After logging in, you just type the command and let the server do the rest.
  After the server has started, you will see at least one xterm, and perhaps a couple other xclients (clock, calculator, etc) too. This will depend upon your local system.
- You can tailor the manner in which the X server starts by creating a file called .xinitrc in your home directory. A sample .xinitrc from an IBM AIX system is provided HERE.
Starting the window manager.
- A window manager is essential for working productively in the X Windows environment. Many systems will start one for you automatically.
- There are several window manager programs in wide use. Those available to you will depend upon your local system. Some common window managers are:
```
 
     uwm   - Universal Window Manager 
     twm   - Tom's Window Manager 
     mwm   - Motif Window Manager 
     awm   - Ardent Window Manager 
     rtl   - Tiled Window Manager 
          
```
- The easiest way to tell if a window manager is running is to look for a "border" around your X clients. For example, an xclock with and without a border appears below:
- If you need to start the window manager manually, simply type its name and put the process in the background. For example, to start the Motif Window Manager:
```
     mwm  &  
```
  You may also be able to add a command as the last line of your .xinitrc file to automatically start the window manager when you start the X server. For example, to start the Motif Window Manager:
```
     exec mwm  
```
- After starting the window manager, your X clients will have borders and be able to be controlled (move, resize, iconify, etc) via your keyboard and mouse.
Starting the first xterm terminal emulator
- A terminal emulator is an X client that looks like a rectangular window and acts as a terminal screen. It accepts input from you and will also display program output. Most of the work you do will be done inside an xterm window.
- The most common terminal emulator xclient is called xterm.
- At least one xterm should be started automatically whenever the X server is started. If this doesn't happen, contact your local System Administrator for assistance.
- If you want to open another xterm, type a command similar to the one shown below at the first xterm's prompt:
```
     xterm  &  
```
Running X clients on other machines
- Because X Windows is a network based system, you can run X clients on machines across the network and send their displays back to the machine which is in front of you.
- You can also run an X client on any network machine and send its display to any other network machine, provided that the necessary permissions are setup.
- To run an X client on another machine:
  1. Give the other machine permission to send X displays to your local machine with the xhost command:
```
     xhost +othermachine 
```
  2. Start the X client on the other machine. This can be done at least three different ways:
    1. Use the rsh command and include the -display option. For example, the following command will start an xterm on machine kanaha and send the display back to machine makena. Note that in most cases, the display machine name must be suffixed with ":0".
```
     rsh kanaha xterm -display makena:0 &
```
    2. Login to the other machine and start the X client there after you set the DISPLAY environment variable to point to your local machine. Again note that the display machine name must be suffixed with ":0".
```
     
     telnet kanaha
     { enter userid and password  }
     setenv DISPLAY makena:0 &
     xterm &
                    
```
    3. Login to the other machine and start the X client there using the -display option to point to your local machine.
```
     
     telnet kanaha
     { enter userid and password  }
     xterm -display makena:0 &
                    
```

Using the Window Manager

The following discussion pertains to the Motif Window Manager. Other window managers will have similar functionality but behave differently. This discussion also assume a basic familiarity with using a mouse.

Root Menu

The Root Menu provides a pop-up list of the basic window manager functions. Some of these functions include:


     New Window     - open a new xterm 
     Resize         - resize window 
     Move           - move window 
     Lower          - put window below other windows 
     Raise          - put window above other windows 
     Shuffle Up     - raise window one level 
     Shuffle Down   - lower window one level 
     Refresh        - refresh window 
     Clients        - pop-up list of X clients 
     Restart        - restart the window manager 
     Quit           - quit the window manager

The Root Menu will appear if you press and hold the right mouse button. Make sure that the pointer is not pointing on an X client - it should be pointing to an open area on the screen.
You can select a function from the Root Menu by holding the mouse button and sliding the pointer until the desired function is highlighted/raised. Releasing the mouse button will select the function.

Window Frame
- The window frame surrounds the X client and consists of
  - title area
  - minimize button
  - maximize button
  - window menu button
  - four sides
  - four corners
  A sample window frame which surrounds an xterm appears below.
- Title area: In addition to displaying the client's title, the title area is used to move the window. To move the window, place the pointer over the title area, press the left mouse button and drag the window to a new location. A wire frame is moved during the drag to indicate the new location. When the button is released, the window is moved to the new location.
  Also selected window functions (move, resize, lower, etc) can be displayed by placing the mouse cursor on the title bar and holding down the middle mouse button.
- Minimize button: Located in the upper right hand corner. To turn the window into an icon (an icon is a small image), click the left mouse button on the Minimize button
- Maximize button: Located in the upper right hand corner. To make the window fill the screen click the left mouse button on the Maximize button
- Window Menu button: Located in the upper left hand corner. To pull down the window menu, place the pointer over the button and press the left mouse button. While pressing the button, drag the pointer on the menu to your selection and release the button when your selection is highlighted.
- Sides and Corners: Any of the four sides or corners can be used to resize the window. Simply place the pointer over the frame component and press the left mouse button. While holding the button, drag the pointer in the desired direction. A wire frame is moved during the drag to indicate the new size. When the button is released, the window is resized.

Special Keys

In addition to using the mouse to select window manager functions, you may also use "special keys" to accomplish the same tasks.

Which keys are "special" depends upon your local system. In most cases they are the CTRL, ALT and Function keys. For example:


     ALT + F3    - lower window   
     ALT + F4    - close window  
     ALT + F5    - restore window  
     ALT + F7    - move window  
     ALT + F8    - resize window  
     ALT + F9    - minimize window  
     ALT + F10   - maximize window

Special keys may also be used in combination with the mouse buttons. For example:


     ALT + left button     - lower window  
     ALT + middle button   - resize window  
     ALT + right button    - move window  
     CTRL + left button    - xterm client: options menu  
     CTRL + middle button  - xterm client: vt options  
     CTRL + right button   - xterm client: vt fonts

Cutting and Pasting
- The mouse can be used to cut text from any window and paste it into any other window. This feature saves time and helps eliminate typos.
- To select text, place the pointer at the beginning of the text and then press and hold the left mouse button. As you drag the mouse, the selected text will be highlighted by reverse video. The pointer is your guide to text selection.
- When you have selected the desired text, release the mouse button. The "cut" text will be stored in a buffer.
- Place your pointer in any window which accepts text, and then click the middle button to "paste" the text. Note that if you are in the vi editor, your paste will need to be done while the vi session is in "input" mode.
- Cutting and pasting can be done on the command line also.
Widgets
- X clients frequently display buttons, scroll bars and slider bars to permit interaction. In most cases, the mouse is used to interact with these "widgets"
- Buttons: click with the left mouse button (in most cases)
- Scroll bars: clicking with the left mouse button will usually scroll one line/screen, depending where you click. The scroll bar can often be "grabbed" by pressing and holding the middle mouse button and then dragging to the desired point.
- Slider bars: work like scroll bars.
- Other widgets: usually intuitive - experiment.
Customizing your window manager
- The default behavior of your window manager is usually defined in a system configuration file. For example, the default configuration file for the Motif Window Manager might be defined in /usr/lib/X11/system.mwmrc .
- Most window managers permit you to define your own configuration file. Motif, for example, can be configured by a file called .mwmrc in your home directory.
- A sample Motif configuration file may be here.
- Additional details on constructing your Motif configuration file can be found in the mwm man page .

Customizing Your X Clients

Default X client resource specifications are usually kept in the directory: /usr/lib/X11/app-defaults
Most X clients permit you to customize various parameters, such as geometry (size), color and fonts.
Customizations can be specified as command line options or in an "X Resources" file, called .Xdefaults located in your home directory.

Some common command line options are listed below.


     -background     - background color 
     -bg             - background color 
     -foreground     - foreground color 
     -fg             - foreground color 
     -bordercolor    - color of window border  
     -bd             - color of window border  
     -borderwidth    - border width 
     -bw             - border width 
     -font           - font for text 
     -fn             - font for text 
     -display        - display for client  
     -geometry       - window size and placement 
     -iconic         - start window as an icon 
     -name           - name to display on title bar 
     -title          - name to display on title bar

In order to do further customization via an .Xdefaults file, you need to know the actual resource specification. These are unique for each X client. An example .Xdefaults file can be viewed here.
Colors
- Many X clients allow you to alter their default colors. The colors available to you will depend upon your system, but can usually be found by reviewing the file: /usr/lib/X11/rgb.txt
- X colors are specified as RGB values. Each color is a composite of three primaries (Red, Green, Blue). The intensity of each primary is specified as a value from 0 to 255. For example, the rgb.txt mappings for several colors appear below:
```
     255   0   0     Red
       0 255   0     Green
       0   0 255     Blue
     255 240 245     LavenderBlus
     255 228 225     MistyRos
     240 255 255     azur
     224 238 238     azure2
      93 205 205     azure3
          
```
- X client colors can often be set with command line options. In the example below, an xterm is created with a blue background and white foreground (text):
```
     xterm -bg blue -fg white &
```
- For more detailed (and permanent) color specifications, the .Xdefaults file can be used. For example, the following lines might be used to set xterm colors:
```
     xterm*background:       DarkSlateBlue
     xterm*foreground:       LemonChiffon
     xterm*cursorColor:      red
     xterm*pointerColor:     red
          
```
- Although it is usually easiest to just use the color name, colors can also be specified in hexidecimal format. This may be useful if you need a color that isn't available on the system by name:
```
     #000000         black 
     #FF0000         red
     #00FF00         green
     #0000FF         blue
     #00FFFF         cyan
     #5F9F9F         cadet blue
          
```

Fonts

Many X clients permit you to specify alternate font(s) for text. The fonts which are available to you depend upon your system, but they can usually be found by reviewing the file: /usr/lib/X11/fonts/fonts.dir.
You can also use the xlsfonts utility to list all of your system's available fonts.
Full font specifications are very detailed. Wildcards (*) can also be used. For example:


   1      2     3   4  5       6  7  8  9 10 11  12
-adobe-courier-bold-o-normal--10-100-75-75-m-60-iso8859-1 
-adobe-helvetica-bold-r-normal--*-120-*-*-*-*-iso8859-*

     1= foundry
     2 = font family
     3 = weight
     4 = slant
     5 = set width
     6 = pixels
     7 = points (in tenths)
     8 = horizontal resolution in d.p.i.
     9 = vertical resolution in d.p.i.
    10 = spacing
    11 = average width (in tenths of a pixel)
    12 = character set

The xfd utility is helpful for viewing a font before you actually use it. For example:
```
     xfd -fn Rom14 
```
A sample xfd display can be viewed here.
Specifying a font with a command line option:
```
     xterm -fn Rom14 & 
```

Specifying fonts in the .Xdefaults file:

     
Mwm*fontList:    -ibm--medium-r-medium--20-14-100-100-c-90-*
*icon*fontList:  fixed
aixterm*font:    Rom14.500
Vt*.fontList:    Rom10
emacs*font:      Rom14.500

Geometry
- All X clients that display in a window allow you to specify their size and location on the screen by using the geometry option:
- The syntax is:
```
     -geometry width x height +/- xoffset +/- yoffset
      
     width = in pixels usually; in characters for xterm
     height = in pixels usually; in rows for xterm
     +xoffset = pixels from left edge of screen
     -xoffset = pixels from right edge of screen
     +yoffset = pixels from top edge of screen
     -yoffset = pixels from bottom edge of screen
      
     
```
- Example 1: Creates an xclock 125 pixels wide by 125 pixels high and places it 10 pixels from the right edge of the screen and 20 pixels from the top of the screen.
```
     xclock -geometry 125x125-10+20 & 
```
- Example 2: Creates an xterm 132 characters wide by 40 rows and places it 10 pixels from the right screen edge and 350 pixels from the top of the screen.
```
     xterm -geometry 132x40-10+350  & 
```

Some Common X Clients

A list of some common X clients appears below. Note that there are many X clients available which do not appear here. Also, some of the clients in the list below are linked to their man page. For additional information, consult an X Windows reference.

bitmap - system bitmap editor and conversion utilities
resize - reset terminal settings to current window size
xbiff - mailbox flag
xcalc - scientific calculator
xclipboard - text clipboard
xclock - continuous analog or digital clock
xdm - X display manager
xdpr - dump an X window display to a printer
xedit - simple text editor
xfd - font displayer
xhost - server access control program
xinit - X server initializer
xkill - kill an X client
xload - load average display
xlogo - display the X logo
xlsfonts - list fonts
xmag - magnify parts of the screen
xman - display man pages
xmh - X Window interface to MH mail system
xmodmap - keyboard and pointer modifier
xpr - print an X window dump
xprop - display window and font properties for X
xrdb - X server resource database utility
xrefresh - refresh all parts of an X screen
xset - set user preference options
xsetroot - set root window parameters
xterm - terminal emulator window
xwd - create X Window dump
xwininfo - display window information
xwud - display (undump) an X window dump file

This concludes the tutorial. Return to the Table of Contents