好心人帮助一下，这是什么问题，谢谢
compiling Fortran...
D:\n\wendu.for
Linking...
wendu.obj : error LNK2001: unresolved external symbol _C@12
Debug/wendu.exe : fatal error LNK1120: 1 unresolved externals
Error executing link.exe.
wendu.exe - 2 error(s), 0 warning(s)