   link error 2019 why?give me some tip  pleaase
  linking... welcome_service.obj : error LNK2019: welcome_service.obj : error LNK2019: welcome_service.obj : error LNK2019: welcome_service.obj : error LNK2019: welcome_service.obj : error LNK2019: welcome_service.obj : error LNK2019: .\ReleaseDebug/welcome_service.exe : fatal error LNK1120: 6    
  You're not linking some library. I can't give any more help unless you tell us what symbols are unresolved, and what libraries you're linking to.   ;  Clearly your externals are unresolved... you should try resolving them   ;  yes~  im wonder~~ why that no tip to tell me what worng with lib~  why no tip  and just tell 2019 2019 2019 ~~~   ;  sorry~what is externals mean?  english not my prime language   ;  Externals are functions in other parts of your program (either other source files, or other libraries (.lib or .dll files)). That linker error means that the linker can't find one or more functions that were referenced. What are the full errors? That'll tell you what functions it can't find, and we might be able to work out what librar(y|ies) you need to link in.   ;  thank you too much~  but  that is all~~  i also wonder why just that~ doyou have any idea what cause tht?   ;  What Steve was saying is that you haven't got a Source File linked in your project, or you haven't got a library linked into your project.You are probably including a header file for some functions that are contained within a library or another source file, that the linker cannot find because it is not ... linked ... with the current project or build.   ;  What compiler/linker are you using? That alone would help a bit more... By the looks of it, it's a Microsoft compiler/linker. However, all the MS linkers gave much bigger error messages than just LNK2019.Paste the entire>(That is, all the error text) error message.Toolmaker   