OS/2 Version 2.0 provides application compatibility at the executable code level for applications written to run under previous versions of OS/2. Hence no modification is necessary to enable such applications to run under Version 2.0. However, in order to take full advantage of the enhanced capabilities of OS/2 Version 2.0, such as the 32-bit flat memory model and the additional features implemented by Presentation Manager, applications will require modification of their source code.
Application developers who wish to migrate their code to the 32-bit programming environment under OS/2 Version 2.0 should experience little difficulty. Changes between the OS/2 Version 2.0 programming environment and that provided under previous versions of OS/2 fall into the following basic categories:
The remainder of this chapter will describe each of these categories in detail, and suggest methods by which the required changes may be made.
Note that it is not mandatory for an application to migrate all its modules and resources to the 32-bit programming environment. OS/2 Version 2.0 allows mixed model programming, where 32-bit applications may make use of existing 16-bit modules and resources. The subject of mixed model programming is discussed in Mixing 16-Bit and 32-Bit Application Modules.