Question about the X Server

[Igor Korot]

Hi,
As far as I understand the X is just a universal GUI environment for the UNIX/LINUX world. On top of X there are other shells, like the KDE or GNOME.
KDE is based on the QT library that is well documented and the developers wjo wants to develop the KDE/QT program can read the doc about QT-specific functions.
The same goes for the GTK/GNOME.

However, looking at ww.x.org, I could not find any info on the functions that can be used in developing GUI application under the X.org.

Could you point me ou to this location?

Thank you.