Complete Operating system

[PapaParrot]

What makes a complete operating system ? Years ago when the MS windows program was made, one thing about it was it was not a complete operating system, it was just a program, and required Dos to boot and start the computer, so any way, I never pursued MS windows and don't know much about that, but lately I have been noticing a trend, including the Linux's , I no longer use Linux either for various reasons, but any way since I do read various discussions about it , and questions about the many problems that seem to occur , I started wondering if Linux really can be considered a complete OS, I mean from what I have been seeing, it can not boot without some kind of boot loader, Grub2 being the standard default, even though there are others.
3 OS's, that I do consider complete OS's, none of which require or are dependent on some other system to boot, FreeDos, boots on it's own, no need for Grub2 or any other boot loader, also OpenBsd does not require any thing like Grub ,Lilo, etc,... and then even Minix3, boots just fine with out any other program to boot it.
I do realize that when people want multi boot systems , a menu of some sort is helpful, for selecting which system to boot, but I am referring to just a single OS, it seems Linux is not capable of booting by it'self , like MS windows, it requires a "boot loader" of some sort, or maybe I am wrong, can Linux boot , without Grub,Lilo, or some other boot loader, ?