无论在编译什么程序的时候，都会出现这样的错误。（程序是正确的）。是什么原因？
[Linker Error] Unresolved external '_Form1' referenced from D:\BORLAND C++ BUILDER 6\PROJECTS\PROJECT1.OBJ
[Linker Error] Unresolved external 'TForm1::' referenced from D:\BORLAND C++ BUILDER 6\PROJECTS\PROJECT1.OBJ