MDB provides support for debugging 64-bit programs. Once it has examined the target and determined its data model, MDB will automatically re-execute the mdb binary that has the same data model as the target, if necessary. This approach simplifies the task of writing debugger modules, because the modules that are loaded will use the same data model as the primary target. Only the 64-bit debugger may be used to debug 64-bit target programs. The 64-bit debugger can only be used on a system that is running the 64-bit operating environment.