Can you use a camera while it's charging?

I have a Nikon D40X and it wouldn't turn on in the car so I plugged it in and I still can't turn it on. Is it broken or is it just cause it's still dead?

If the battery is charging, then, you have to wait until it's fully charged. It can be done overnight.

Are you trying to charge it through the USB port?

the only way to charge it is to take the battery out and charge the battery. No battery=no power for camera

I thought that with Nikon dSLRs, you have to take out the battery (EN-EL something something) and insert it to the charger which plugs to the wall socket. How are your charging the camera in your car? The USB port is for file transfer only. Do you have a dead camera? I won't be surprised if you already do.