OSDev.org

It is possible for one person to program a whole operating system by oneself, or it is necessary get a team to develop one?

Thank you.

It is quite possible for one person to develop an OS from scratch. Assemblers, compilers, kernel, device drivers, windowing system, network stack, web browser, everything.

That said, it's a lot of work, and you might consider trying to get some outside help once you have the basic stuff working.

the best way is to start it yourself, get the base system working to your like.  Then you have a say in the direction.  

Little tip, when making the OS start by designing a basic library (like libC) for the kernel, including basic functions like stdio, conio, etc.  Then you give the library to developers, and the coding goes much smoother.

Yes it is quite possible. But you must have a LOT of free time. I spend on my OS 2-3 hours daily, since 2 years with few breaks. And its still version beta
But it was worthly.