When you said OPERATING SYSTEM, you mean no sofware/disc that suppose to come with the camera?
If that the case, Nikon usually sale their photo editing software separately, unlike canon; it includes it. You might need to purchased it from Nikon or photography store or just use Adobe Photoshop if you have one, I believe the softwares that can be downloaded from nikon requires full install from the CD. Things that you might be able to download from nikon without the CD are Utility Tools, RAW conversion, Printer tools and drivers.
I'm not talking about photoshop or similar. I am actually talking about the guts of the camera. The operating system that makes the camera function.