Is it necessary to update OS X El Capitan for updating xcode version 9.0.1 ?
can anyone know this thing ?
Here https://developer.apple.com/library/content/releasenotes/DeveloperTools/RN-Xcode/Chapters/Introduction.html you can see the requirements for Xcode 9.0.1:
Xcode 9 requires a Mac running macOS 10.12.6 or later.
So, yes, you have to update at least to macOS Sierra unfortunately. OS X El Capitan is version 10.11.