Hey Arun,

I would like to tell you that B.E Computer Science is not at all hard. It all depends upon your interest in the field which you have choose. It is not necessary for one to have prior knowledge about computer science field before pursuing it.

However, if you are interested in learning some of the basic concepts then basic programming knowledge can be useful, knowledge of basic text editors like sublime Text, Notepad++ etc, basic knowledge of Programming languages like C, C++, Java etc.

Nowadays, many online courses are available for learning basic programming languages. You can take one of them. Even if one doesn't have any prior knowledge of this field than also one can take computer science because one must be curious to learn new things and that is what all matters.

Hope this helps : )