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Q43276: Applications and the Math Coprocessor Under Windows

Article: Q43276
Product(s): Microsoft Windows Software Development Kit
Version(s): WINDOWS:3.0,3.1
Operating System(s): 
Keyword(s): kb16bitonly
Last Modified: 06-NOV-1999

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The information in this article applies to:

- Microsoft Windows Software Development Kit (SDK) versions 3.0, 3.1 
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SUMMARY
=======

When an application for Microsoft Windows is run on a machine with a math
coprocessor, the application can use inline floating-point instructions to take
the fullest advantage of the hardware.

MORE INFORMATION
================

Specifying the -FPi option on the C compiler command line causes the Microsoft C
optimizing compiler to produce inline 80x87 math coprocessor code for any
floating-point math operation. If this code is linked with the WIN87EM.LIB
library and a math coprocessor is present in the system at run time, the
application will use the inline floating-point instructions for its math
operations. If no coprocessor is available at run time, code in the emulator
library evaluates floating-point expressions.

An application compiled for the MS-DOS environment with the -FPi option checks
for the coprocessor at run time and modifies its code accordingly: if there is a
coprocessor, it uses inline floating-point instructions; if there is no
coprocessor, it calls software routines to emulate the coprocessor.

In the Windows environment, these run-time modifications are not performed
because the Windows kernel fixes up the floating point references as it loads
the application's code segments (the kernel is aware of the presence or absence
of the numeric coprocessor). This means that an application for the Windows
environment compiled with the -FPi option will perform direct, inline
floating-point instructions without run-time coprocessor-checking. Consequently,
there is no need to link in the Microsoft C Compiler inline floating- point
module, which removes the run-time coprocessor-checking.

Additional query words: 3.00 no32bit 3.10

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Keywords          : kb16bitonly 
Technology        : kbAudDeveloper kbWin3xSearch kbSDKSearch kbWinSDKSearch kbWinSDK300 kbWinSDK310
Version           : WINDOWS:3.0,3.1

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