X11/XLib.h missing ?

[marc dobler <marc actsc tokai jaeri go jp>]

hi everybody ! 

currently, i use RH_8 with KDE. 
i downloaded some program which needs the 
/usr/X11R6/include/X11/Xlib.h library file. 

BUT, there is none on my system. 
when i search it, i get : 
> locate Xlib.h 
/usr/lib/xemacs-21.4.8/i386-redhat-linux/include/extw-Xlib.h

is this file the same as the previous ? 
if yes, how to configure the system to get it seen from the install ? 
if not, where to find a Xlib.h ? 

thanks for help ! 

Marc