newbie question

[Preetham]

Hi all:

I have a very elementary question. How does the Winodws program run in Unix. For example, i write a program where i call the CreateBitmap() method, what happens. How is a dll called in the unix environment. From what i know, unix dlls are .so files. From the wingdi.h file in the wine\include directory, how does the unix OS know how to resolve the WINAPI call. If i am right, windows dll's are implemented in unix, how is this done.
I'm kinda flustered at the moment, would appreciate the help
Thanks,
Preetham.