PIC16F874 Math Routines

Microchip has a library of fixed-point and floating-point math routines.  Two of these are available here.
Here are the two "include" files which must be used in conjunction with the math routines.  They define the target device and specify the locations of the registers used by the routines.
Below is an example of a program which uses the above two routines.  It doesn't do anything much with them but it does illustrate how to include them in your code.  The comments within it clarify a number of points.
Complete Documentation for the PIC16 Math Routines (1.6 MBytes).  This documentation is from Microchip and describes all the routines in the library, not just the two provided above.  This documentation does not include an example of how to include the routines in your own source code, which is why I wrote the example program above.  In addition to explaining what registers are used by the routines, the documentation discusses the algorithms involved and includes the complete source code.  However, since the file is in Portable Document Format (PDF), it's probably easier to get the source code directly from Microchip rather than extracting it from the PDF file.  The source code is provided in .zip format.