Microsoft Corporation documents the Windows APIs in two main places: in the Microsoft Software Developer's Kit (SDK), and on the Web site, msdn.microsoft.com. Both of these are excellent sources of information on the various Windows API functions. In order to learn how to access and use a Windows API function, you need to refer to these documents frequently.
In the documentation for each function, you can learn the DLL name that contains the function (the DLL name to call) and whether or not ANSI and Unicode versions are available (for functions that handle text). All of this information is listed in the requirements table for the function.
If both Unicode and ANSI versions of the function are available, you must append an "A" or "W" to the function name when you call it in ACUCOBOL-GT. "A" stands for ANSI, "W" for wide code/Unicode. For instance, the GetUserName function is implemented as GetUserNameW (Unicode) and GetUserNameA (ANSI). In some cases, the requirements table supplies the function names for Unicode and ANSI. In other cases it simply states:
Unicode: Implemented as Unicode and ANSI versions
Either way, be sure to include the "A" or "W" in the function name to indicate which version you want to call.
Note that Windows API function names are case sensitive. You must adhere to case sensitivity of the function name when you call it.
Finally, the Microsoft documentation defines the parameters for the Windows API functions. You will create variables for each of these parameters in your program's Working-Storage Section.