How To Build Your Console

This is quite beyond ambitious. I wouldn't worry about programming the OS until you have an expert level understanding of electronics (maybe you already do). There was a similar thread here not so long ago which might have some useful information in there but I can't find it right now. The responses weren't very encouraging though and I suspect you will likely get similar responses. It is a major under taking. You'd be better off working on something that already exists and making it console like (basic PC with inux, raspberry pi). You could make usb type peripherals for it then.

Edit: I think this was the thread I was referring too:

http://www.gamedev.net/topic/676821-where-can-i-learn-to-create-a-server-for-a-homebrew-game-for-my-own-console/

As a said, hardly encouraging responses but realistic.

No.

You are talking about devices that cost a fortune to develop. An individual can make small custom boards, the type of system seen in the 1970's, but more than that is unrealistic unless you have a team of people with degrees in electrical engineering, computer engineering, and similar.

You mentioned the Raspberry Pi. That is a good start down the path.

Ok. I think I might find code to copy on the Internet, or save up for a raspberry pi.

Raspberry Pi is a great choice and it is VERY affordable. I think they have done a model that costs only $5.

reminds me of http://www.xgamestation.com/view_product.php?id=33

they're selling very basic console hardware and all the stuff you need to learn how to program these and how they work.

edit:

seems like they've moved, but they offer still the same set of small consoles:

http://www.ic0nstrux.com/products/gaming-systems

There are a couple of kits here that may be what you are looking for, specifically the XGameStation and the HYDRA Game Development Kit, that allow you to build an 8 bit console from scratch and learn to program games for it.