27 of 97    27 The program is now asking us whether we wish to run in  READ ONLY  mode, or READ / WRITE mode.  Some operations performed after selecting a SelFil involve writing information back to the database.  SelFils used for these types of operations must be set to READ / WRITE mode.   However, READ ONLY  is good enough for our purposes here, and since the program runs faster when in READ ONLY  mode, leave it set that way and hit  [ENTER]. The commands should once again be visible along the bottom edge of the screen now.  Using the left and right arrow keys, move the highlight over to the word  SAVE and hit  [ENTER].  Then, using the left and right arrow keys, move the highlight over to the word  QUIT and hit  [ENTER]. Whichever method you have chosen to sort records by, either Sorting by Last Update or Sorting by Custom Flags, the SelFil you have designed will filter out all of the records that we want to deal with, namely those which have been updated due to additions or deletions.  You must now tell the program what data items you wish to retrieve from those particular records.   You will most likely want to export the Parcel ID, Current Land Value and Current Building Value for each of the modified parcels.  Following a brief explanation of the different file types commonly employed when exporting data, we will continue with our example and design an Export Format Table that will allow us to obtain those new values in the form of an exported file.