I have a created a small user interface in C++ using Graphics.
Now i want to extend it. Such as i want to make it bootable, or how can it act as an Operating System?

Are you talking about a graphics.h header? As far as I know, most people have stopped using these in favour of some more advanced/modern OS libraries. Take a look at this.

As for making it bootable, I would get a Linux distro and modify it to boot your program.

thats fine, but i have no other alternative than graphics.h as i am using turbo c++ for building this. Is there any other alternative?