This is part of Win16 API which allow to create versions of program from one source code to run under OS/2 and Win16. Under OS/2 program can be running under Win-OS/2 if program is Windows NE executable, and with help on Windows Libraries for OS/2, if it is OS/2 NE executable. Here is a WLO to OS/2 API mapping draft

Win16 personality

BIOS API

DOS API

XMS API

Task List API

DOSX API

LOGO API

Screen grabbers API

Task switcher API

SYSTEM driver

KEYBOARD driver

MOUSE driver

DISPLAY driver

KERNEL library

GDI library

USER library

LZEXPAND library