Migrating from Delphi 2
You'll find that a high degree of compatibility between Delphi 2 and the later versions means a smooth transition into a more up-to-date Delphi version. However, some changes have been made since Delphi 2, both in the language and in VCL, that you'll need to be aware of to migrate to the latest version and take full advantage of its power.
Changes to Boolean Types
The implementation of the Delphi 2 Boolean types (Boolean, ByteBool, WordBool, LongBool) dictated that True was ordinal value 1 and False ordinal value 0. To provide better compatibility with the Win32 API, the implementations of ByteBool, WordBool, and LongBool have changed slightly; the ordinal value of True is now -1 ($FF, $FFFF, and $FFFFFFFF, respectively). ...