What do these errors mean?

main.obj : error LNK2001: unresolved external symbol "public: __thiscall Weekly::Weekly(void)" (??0Weekly@@QAE@XZ)
main.obj : error LNK2001: unresolved external symbol "public: __thiscall Daily::Daily(void)" (??0Daily@@QAE@XZ)
main.obj : error LNK2001: unresolved external symbol "public: __thiscall Onetime::Onetime(void)" (??0Onetime@@QAE@XZ)
Daily.obj : error LNK2001: unresolved external symbol "private: static int Daily::num_of_Dappointments" (?num_of_Dappointments@Daily@@0HA)
Debug/Proj5B.exe : fatal error LNK1120: 4 unresolved externals
Error executing link.exe.

If necessary, I can put up some scource code, but there are 13 diffrent files, and I have not a clue where the error is.

>What do these errors mean?

They mean you refer to these identifiers in your code, but never define them. Perhaps they are only declared or, in the case of the constructors, are defined with different parameters.