这样的错误怎么改?

--------------------Configuration: WinMian - Win32 Debug--------------------
Compiling...
WinMian.cpp
Linking...
LIBCD.lib(crt0.obj) : error LNK2001: unresolved external symbol _main
Debug/WinMian.exe : fatal error LNK1120: 1 unresolved externals
Error executing link.exe.WinMian.exe - 2 error(s), 0 warning(s)