DEAR SIR, I WANT TO DEVELOP MY OWN SIMPLE O.S. SO I WANT MATERIAL OR SOURSE CODE ABOUT IT. THANK YOU, ANAND

it depends what type of OS you want to build. The source code for Linux and many other system V variants is freely available (check www.kernel.org). The source for Berkeley 4.4B SD Lite Unix (in my opinion, the most powerful and mature UNIX) is also available (an excellent OS based on 4.4BSD Lite is called freeBSD). Of course, you will probably want to start with the basics. You will definitely need to learn C (probably a little C++ and assembly, too). You will need to get very comfortable with x86 architecture (I am assuming that you are building an OS for the i386 platform). So learn C, assembly, and the details about x86 architecture. Then, browse through the source code for the linux and freeBSD kernels. You will then be prepared to build your own "simple" OS (an OS is certainly not a simple thing to make).