Please always mention which tool you are using. I will explain how to do this in QGIS because it's free.
Open your shapefile. Open the attributes table. At the bottom create a new columon, call it 'test' or whatever. Now click on advanced search. Type 'P_Area = PC_Area' (without quotes) in SQL where clause. Hit OK.
Now click on 'Open field calculator' (ctrl+I). On the top check 'update existing field' and 'only update selected features'. In field calculator, type '1'. Hit ok.
Now, go back to advanced search, this time search for 'P_Area != PC_Area'. Do same steps as above, except input '0' in field calculator instead of '1'.
I am sure you can do it in a smarter way, but hey, this works. :)