I have two html files e.g. abc.html & rst.html. abc.html has inline script having a variable x declared inside it with some value. Now I want to access the x value inside rst.html file's inline script. Could you please let me know if this is possible.
You can't.
JavaScript does not let you access other tabs (to some extend, you may be able to access <iframes>s which could be in a separate window, but that's it and newer browsers generally prevent such accesses).
While in your browser, you have access to one set of global variables that are in that one window. Anything else is not accessible for security reasons.
The only way you would be able to do that is by using AJAX to read the second file and then search for the variable and grab the value. Good luck doing that...
The simplest for you will be to create a file, say x.js, and load that in both HTML pages. Now you will have access to all the data found in x.js.