Switching on Dephi compatibility mode has the following effect:
     
- 
  1. 
 - Support for Classes, exceptions and threadvars is enabled.
     
 - 
  2. 
 - The objpas is loaded as the first unit. This unit redefines some basic types: Integer is
     32-bit for instance.
     
 - 
  3. 
 - The address operator (@) is no longer needed to set event handlers (i.e. assign to
     procedural variables or properties).
     
 - 
  4. 
 - Names of local variables and method parameters in classes can match the name of
     properties or field of the class.
     
 - 
  5. 
 - The String keyword implies AnsiString by default.
     
 - 
  6. 
 - Operator overloading is switched off.