Compilation of giac with Visual C++ Express Studio 2009 (the free version)
  1/ Install visual c++ http://msdn.microsoft.com/fr-fr/express/aa975050.aspx
  2/ Install gmp for visual c++
  3/ Untar giac (tar xvfz giac-x.x.x.tar.gz). 
  Copy config.h.vcc to config.h in the src directory
  4/ Create a giac directory inside Visual C++ include directory and
  copy all *.h files from src to the visual c++ giac directory
  
  A/ Method 1 from inside visual c++ IDE
  4/ Create a new giaclib project: static library. 
  Overwrite giaclib.vcproj from this directory after editing it
  for path replacements
  5/ Generate the library with nodefaultlib (project options)
  6/ You can check a little program using the library with another project
  and the source file src/giac_oo.cpp
  
  B/ Method 2 from inside cygwin if installed
  4/ From the Visual c++ command line run cygwin with \cygwin\cygwin
  5/ go in the giac src directory
  6/ make -f Makefile.vcc
  7/ You can compile giac_oo.cpp
     cl /Zi /I. /EHsc giac_oo.cpp giac_oo.lib gmp.lib