Depends on the laws in your state. In SC, a non-CWP gun carried in a car must be in a closed compartment. In NC, it must be openly displayed either on the seat or dashboard. In SC, there is NO open carry on your person. In NC, you may carry openly except under certain conditions and places. Both NC and SC have CWP available by taking a test. In NC, you must purchase a handgun permit to buy a gun. Not in SC. You must fill out the 4473 and have the background check done in both states. In SC, a CWP holder still must fill out the 4473, but the background check is waived.
Now - your gun is in your car. You're 50 feet away, walking out of the store, when someone tries to mug you. What good does that gun do you?