Anyone who can legally buy a handgun can keep a handgun in their vehicle in SC, loaded or unloaded, as long as it's in the glovebox, center console, or a container with an integral locking fastener.
SC permits concealed carry only.
Can't carry anywhere alcohol is sold for on-premise consumption, or any place posted according to the signage statute. Highway rest stops are OK. Government buildings are not, nor medical offices and hospitals.
If you get pulled over you must inform the officer that you're carrying and produce your permit.
You can look up all the statutes at http://www.scstatehouse.gov/code/statmast.htm