Whether you work or get the day off on Monday depends on what you do -- and where you do it -- for Uncle Sam.

Status and geography are the qualifiers for the Inauguration Day holiday.

If you are a Commerce Department clerk downtown, or a research scientist in Beltsville, have a nice holiday! If your office is along the Pennsylvania Avenue parade route, you probably can't even get inside the building on Monday unless you are a VIP.

But if you are a federal computer programmer in Manassas, or an FBI agent based in Silver Spring, chances are you will be on the job Monday as usual. Ditto for postal clerks and letter carriers, who will be selling stamps, sorting, sacking and delivering like any other workday.

Inauguration Day is a holiday for most of the 350,000 federal workers in most parts of the metropolitan area. But many employes -- perhaps as many as 65,000 -- will have to work because of their jobs, or because they work outside the holiday zone that Congress created two decades ago.

The purpose of the quadrennial holiday, not observed in federal outposts, is to clear downtown streets (and federal buildings) for traffic control and security.

However, when Congress set the inaugural holiday rules the metropolitan area was smaller than today. In the past few years, a number of outlying counties and cities in Maryland and Virginia have been added to the area officially designated metropolitan Washington, but they remain outside the holiday pale.

Here's a rundown of who will be doing what on Monday -- and as you read this, keep in mind that nothing in the government is uncomplicated:

* Most federal employes whose offices are located in the District, Montgomery or Prince George's counties, or in Arlington and Fairfax counties, along with the Virginia cities of Alexandria and Falls Church, will be off -- unless they have been designated to work.

* Employes at the U.S. Postal Service headquarters building will get the day off. Workers whose offices are in Virginia's Loudoun, Prince William and Stafford counties, or the cities of Fairfax, Manassas and Manassas Park, must report for work. Fairfax County feds are off, but the lone federal worker based in Fairfax City -- right in the middle of the county -- must work because Fairfax City became an independent jurisdiction after the holiday law was written.

* Postal workers, except for headquarters types, will work Monday. But many will have different schedules. People delivering mail to U.S. buildings downtown will come in early to service their routes before the parade gets under way.

* Air traffic controllers and guards at many federal installations will have to work.

* Many federal medical personnel in veterans' hospitals will be working.

* Law officers from various federal agencies have been drafted to help with security during the Inauguration.

* Washington-based federal workers who are out of town on official business will have to work, even though they would have a holiday if they had stayed home.

* Federal employes from out of town who are here on Monday will, in most cases, have the day off. If they had stayed home, they would have had to work.

Pay and leave status also are complicated. Most employes who get the holiday off will be placed on administrative leave. That means they get straight-time pay for not working. Full-time and part-time feds required to work Monday will get holiday premium pay. Feds whose normal day off is Monday will not be entitled to a day off later in lieu of the holiday.