32-Bit Interface Constraints

The following subsystems, present in OS/2 Version 1.3, have no 32-bit equivalents, since they are not portable and are device-dependent.

VIO

Video subsystem; these function calls should be replaced with Presentation Manager GPI calls or AVIO (advanced video) calls.

Keyboard subsystem; these function calls should be replaced by processing WM_CHAR messages from a Presentation Manager application.

Mouse subsystem; these function calls should be replaced by processing WM_MOUSEMOVE and WM_BUTTON messages.

Device monitor subsystem; these function calls should be replaced by using appropriate message queue hooks in a Presentation Manager application.

Note that these subsystems are supported under OS/2 Version 2.0 as 16-bit service layers, for access by existing applications. However, OS/2 Version 2.0 does not provide thunk layers to enable 32-bit applications to access these service layers. 32-bit applications that use these subsystems must employ mixed model programming techniques to access the 16-bit services; see Mixing 16-Bit and 32-Bit Application Modules for further discussion.

Only two forms of input/output are supported in the 32-bit environment; the stdin/stdout C interface (producing command line-based applications that can be run in a text window) and Presentation Manager applications. Programs wishing to perform graphics, handle keyboard or mouse input, or intercept and modify device information should do so using Presentation Manager functions.

Certain other functions have also been removed from the 32-bit programming interface. These are primarily concerned with the management of memory in the segmented memory model. Therefore functions such as DosSizeSeg(), DosLockSeg() and DosUnlockSeg(), DosR2StackRealloc() etc are not implemented in the 32-bit programming interface, although the 16-bit entry points are still supported for compatibility purposes.