Varchar/Char Compatibility

Dear All, We have found that changing some columns in our databases from char to varchar can save up to 40% of our disk space. Now I know about the update performance overhead, and this will not be a problem for us, since our database uses mainly inserts and deletes. In the 'Guide to SQL: Tutorial Version 4.1' page 10-26, it says: "Furthermore, VARCHAR data is immediately compatible with most existing programs, forms, and reports. (Forms must be recompiled. Forms and reports should, of course, be tested on a sample database.)" This is rather confusing to me, and I was wondering if anyone has tried this in the past and had any problems, or if anyone knows the reason for having to recompile forms (If, indeed, this is necessary). Yours confussedly, Richard Ridley DHL Asia Pacific Singapore