MSVC_VERSION

The version of Microsoft Visual C/C++ being used if any.

Known version numbers are:

1200 = VS  6.0
1300 = VS  7.0
1310 = VS  7.1
1400 = VS  8.0
1500 = VS  9.0
1600 = VS 10.0
1700 = VS 11.0
1800 = VS 12.0