Door locks when window is down?

If I get out of my car when my windows are down, it locks at least the driver's door. I haven't thought about it until now, but I'm not sure if it locks all of the doors or just that one and I'm not sure if it locks at any level, or just when the window is down halfway or more. I've never really tested it. I've always been able to put my arm in and open the door from inside, so it's not been a big problem, but I'm afraid one day I'll end up locking my keys in the car. I bought the car secondhand so there isn't a manual and I can't find anything online about it. Is it possibly a safety feature and is there a way to turn it off? Thank you.