where Is The Xorg.conf File found under Unix / Linux / BSD?

I require to find and edit my xorg.conf file for tweaking and configure it for new settings. The issue is that I'm unable to find the file. according to my research, xorg.conf very should in /etc/X11 or /usr/X11R6/lib/X11/ directory. I found directories but not the file in directories. How do I find the xorg.conf under Unix or Linux like operating systems?  See More..