Many low-level interfaces have been changed in some way; but an effort has been made to limit the required changes in client source code to a reasonable level. Almost all of the required changes should be detectable by the compiler, so a reasonable porting strategy is to rely on the Mimosa compiler for guidance. Look elsewhere for details of the changes, but here are the highlights:
Basics - the move and copy routines have been rationalized, and re-implemented efficiently. Some unused/unimplemented procs have been removed.
Char - This is a new interface describing an extended 32-bit character representation.
Rope - A new variant was added to the record definition that will allow a wide-character supertype of ROPE to be defined. Also, Rope.Cat demands at least 2 arguments, so some uses will need to be changed to Rope.Concat.
SafeStorage - The PFinalize interface is renamed to Finalization. The defunct section of SafeStorage that dealt with old-style finalization has been removed.
IO - There is an explicit buffer added to the STREAM object, so that inline versions of GetChar and PutChar can be provided. There are new provisions for I/O of 64-bit numbers (both fixed and floating point). The PutF* routine now demand an appropriate number of arguments; this may call for a significant amount of (trivial) editing while porting code, but helps control the object code size.
Imager - AIS support is removed from the public interfaces. A new object has been added at the DeviceWorks level. The XChar type is now Char.XCHAR. See ImagerChanges.tioga for details.
Interpress - The "Interpress" interface is now named "InterpressInterpreter".
RopeFile - The RopeFile interface and implementation is very different, no longer assuming a particular file system. Most clients will not use the RopeFile interface directly, but instead will call PFS.RopeOpen.
SunRPC - now supports TCP as well as UDP. A new interface, SunRPCBinding, simplifies setting up a connection. A compatible stub generator is available.
Tioga - Low-level interfaces have been rationalized (and in many cases renamed). [details from Wyatt]