I want to make an os ,so from where I start.
As Phoenix said, I would recommend learning a language or 2 first then this can help you http://www.linuxfromscratch.org/
Thank u all for ur suggestions.
Most operating systems ( major ) are written in c or c++ and have millions of lines of code (correct me people if i am wrong ^^ ) so you should learn some programming language first :)
Staring with C++ might be a good idea, it will help you understand some most demanding programming languages as well.
If you have 0 programming experience, then it will take you probably 1-2 years to actually get the skills needed to begin.
Entire teams can finish it in like a year, but a solo person writing all that code from scratch..
You could made a very poorly written one in a few months, but I don't know the time frame.
Writing an OS requires you to have not only an understanding of a programming language but how to interact with the hardware. When your are programming, you aren't telling the cpu what to do directly, you are telling the os which then tells the cpu. Therefore you need to know how to talk to the cpu. However this can mostly be avoided if you build a linux distro instead as it has the kernel stuff already. I suggest you learn assembly and a bit about the architecture you are targeting(targeting i386 which is intel's 32 bit cpu architecture from 1985 will give you the most audience), if you want to write an completely independent OS. Assembly is imperative no matter which what your are doing, although you could get away with c++ if you are making a distro
Well, it is pretty hard, so I would also recommend linuxfromscratch.com. if you want to help me, see my post about ShadeOS.