X Windows (X11) is the graphical environment for most Unix or Unix-like systems, including *BSD and GNU/Linux; it provides access to screen, keyboard, and mouse. X11 is the Unix and Linux graphics drivers.
Graphics libraries for accessing the X11 protocol:
Top
| Xaw
| Motif
| GTK+
| Qt
| XCB |
| xt |
| Xlib |
| X11 Protocol |
Bottom
Definitions- display
- the machine the which the graphical output will appear.
- screen
- the actual physical display device; in most cases this will be a monitor. X11 allows for an arbitrary number of screens to be connected to each display.
- window
- a rectangular area of the screen that can be used for input and output. If the rectangular area is not directly associated with a screen, but instead resides in memory, it is referred to as a "pixmap". Pixmaps and windows share the property of being "drawable" and can be used interchangeably in some function calls.
- planes
- The number of bits per pixel is also referred to as the number of planes in the graphics display.
programming - target - Xlib
programming - target - XCB
Resources
wikipedia: X Window System
Linux Journal: Learning to Use X11
X.Org documentation for X11R6.8.2
X Windows faqs
Wikibooks - X Window Programming