Question

I want to learn computer science to its roots. how can i start the study.
From where i must start

Answer 1

There are several, high quality computer science classes you can use online, for free. For example:

A full course set.
http://www.saylor.org/majors/computer-science/

Parts:
http://see.stanford.edu/
http://ocw.mit.edu/index.htm

Answer 2

I might go with: https://www.udacity.com/
Its got a few good cources