The f$MODEg sets the compatibility mode of the compiler. This is equivalent to setting one of the
command-line options -So, -Sd, -Sp or -S2. it has the following arguments:
     
- 
Default 
 - Default mode. This reverts back to the mode that was set on the command-line.
     
 - 
Delphi 
 - Delphi compatibility mode. All object-pascal extensions are enabled. This is the
     same as the command-line option -Sd.
     
 - 
TP 
 - Turbo  pascal  compatibility  mode.  Object  pascal  extensions  are  disabled,  except
     ansistrings, which remain valid. This is the same as the command-line option -So.
     
 - 
FPC 
 - FPC mode. This is the default, if no command-line switch is supplied.
     
 - 
OBJFPC 
 - Object pascal mode. This is the same as the -S2 command-line option.
     
 - 
GPC 
 - GNU pascal mode. This is the same as the -Sp command-line option.
     
 - 
MACPAS 
 - MACPAS mode. In this mode, the compiler tries to be more compatible to
     commonly used pascal dialects on the Mac OS, such as Think Pascal, Metrowerks
     Pascal, MPW Pascal.
 
For an exact description of each of these modes, see appendix D, on page 606.