程序检查没有错！F7的时候提示这是怎么回事？？
-------------------Configuration: a1 - Win32 Debug--------------------Linking...
LIBCD.lib(wincrt0.obj) : error LNK2001: unresolved external symbol _WinMain@16
Debug/a1.exe : fatal error LNK1120: 1 unresolved externals
执行 link.exe 时出错.
a1.exe - 1 error(s), 0 warning(s)
