[Eranga]

i am going through a tutorial but i think i don't need to modify autoexec.bat

That's the power of bat files. You can edit AUTOEXEC.bat file, which is heavily use by the OS, through your bat files. But you have to really care about that. You are going to do changes on client machines, and different users have different settings on there bat files. So if something is going wrong they will blame on you.