A federal government shutdown does not mean that everything grinds to a halt. Certain operations that are considered essential will continue to function, although employees required to work will not be paid until after the shutdown ends.

The most visible impact in the Philadelphia area will be at national parks, including Independence Hall and the Liberty Bell, which will be closed. Valley Forge National Park will be open to the public, but all park buildings and restrooms are closed and there will be no educational programs. The Independence Visitors Center is not a federal facility and will be open, though the National Park desk will not be staffed.

Essential operations include law enforcement, such as the FBI, airport security and customs, the military and government-run hospitals.

But even within designated essential operations, there are non-essential employees who are furloughed during a shutdown.

For example, 17 percent of the Justice Department's employees will be furloughed. The agencies with the highest percentage of employees being furloughed include Housing and Urban Development (96 percent) Environmental Protection Agency (95 percent) and Department of Education (95 percent). At the bottom of the list is Veterans Affairs, with 4 percent of its workers furloughed.

Despite the government shutdown, federal courts will remain open and can continue operations for about three weeks, through Feb. 9, by using court fee balances and other funds not dependent on a new appropriation.

The United States Postal Service also will continue to operate.