Adding ceiling light to room
I've seen it done both ways but the feed to the switch is more common. You'll probably have a black and white coming into the switch the black will be pigtailed to the switch and to a black wire going to the outlet. you'll also have a red connected to the switch going to the outlet. The white coming in will be connected to a white going to the outlet. At the outlet the black will be pigtailed to a brass screw and continue to the next outlet, the switched red wire will be hooked to the other brass screw, and the link between the two screws will be removed. the white wire will be pigtailed to the silver screw and out to the next outlet.
If you're fed from the outlet, you'll probably have a switch loop with a hot white wire going from the outlet to the switch and a black wire from the switch to the outlet.
You'll need to run wire to your ceiling light location. Where it's run from depends on what you'll find out when you remove the switch and outlet for inspection... don't disconnect anything until you take a bunch of pictures.
Naturally, there will probably be ground wires that are connected but I left that part out until we know what's there.