Tuesday, January 6, 2009

How to fix OS/2 Family API Calls Problems

This post provide computer help, If windows does not support OS/2 Family API.Windows and Windows 95 do not support 16-bit Windows-based applications coded with OS/2 Family API (FAPI) calls. To fix this error follow the instruction.

FAPI works in the following manner:

1. The code contains references to OS/2 FAPI calls (such as DosOpen, DosRead, and so on).
2. When the program is loaded into OS/2 protected mode, the system loader dynamically links the FAPI calls to the OS/2 system-services DLLs (Dynamic-Link Libraries).
3. When the program is loaded into real mode (MS-DOS or OS/2 compatibility box), what actually gets loaded is a small program called the "FAPI Loader and Linker." It is this program that loads the real code; it dynamically links the FAPI calls to a special library of support routines that translate FAPI calls into 80x86 code and MS-DOS interrupts (INT 21H Function xx).

FAPI works well for programs that need to run in MS-DOS and OS/2 protected mode. The problem is that Windows uses the "New EXE Format" for programs, bypassing the standard MS-DOS entry point. For example, if a Windows program is run outside of Windows (in MS-DOS), the following message appears, and the program terminates:

This program requires Microsoft Windows

MS-DOS is not responsible for this message; the Windows program itself is responsible. The way the Windows program works is very similar to OS/2: it uses dual entry points into the .EXE file. In MS-DOS, a short program that prints the above message runs; however, in Windows, a true Windows-based application runs using the other entry point in the .EXE file.

Therefore, the problem is narrowed down to the following: if the FAPI Loader and Linker program is run using the standard MS-DOS .EXE file entry point, and Windows starts an application using a different entry point, the dynamic linking of the FAPI routines will not occur.

To avoid this problem, do the following:

Instead of using low-level MS-DOS calls (INT 21H Function xx) in a Windows-based application and OS/2 API calls (DosRead, DosOpen, and so on) in a Presentation Manager (PM) application, use the C run-time I/O routines for all of these applications.

This will work because the Microsoft C Compiler and the run-time libraries supply versions of the libraries that work in both OS/2 and MS-DOS. By moving C code to PM and to Windows, it will not be necessary to rewrite it, and the appropriate conversion routines will be supplied at link time.

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