Microsoft KB Archive/39246

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No QB Support for Mixed Languages Compiled with /FPc or /FPa

Article ID: 39246

Article Last Modified on 11/21/2006


  • Microsoft QuickBasic 4.0
  • Microsoft QuickBASIC 4.0b
  • Microsoft QuickBasic 4.5 for MS-DOS

This article was previously published under Q39246


QuickBasic versions 4.00, 4.00b, and 4.50 do not support the use of the Alternate IEEE Math Library (/FPa) or code that generates floating-point calls (/FPc). QuickBasic generates in-line math coprocessor instructions and uses the emulator library. If a math coprocessor is present, it will be used.

Mixed-language routines linked to a QuickBasic routine must be compiled so they generate in-line math coprocessor instructions and use the emulator library. This is the default option for Microsoft C version 5.10 and most other Microsoft languages.


The following is an example of compiling and LINKing a mixed-language application:

   BC bmain.bas;
   CL /c /AM csub;
   LINK bmain + csub /noe;

Note: If the /FPa or /FPc switch was used on the CL command line, the linker may produce "duplicate definition" errors. If you get "duplicate definition" errors at link time, the resulting executable file may or may not run correctly.

Microsoft Basic Compiler versions 6.00 and 6.00b for MS-DOS and MS OS/2 and Microsoft Basic Professional Development System (PDS) versions 7.00 and 7.10 each support the /FPa option for the BC.EXE compiler. However, neither the QuickBasic environment (QB.EXE) that comes with the Basic compiler nor the QuickBasic Extended environment (QBX.EXE) that comes with Basic PDS support /FPa. Therefore, mixed-language programming using alternate math (/FPa) could be accomplished with compiled programs with these products.

Additional query words: QuickBas BasicCom

Keywords: KB39246