Size of a library and the executable

Question

I have a static library *.lib created using MSVC on windows. The size of library is say 70KB. Then I have an application which links this library. But now the size of the final

Answer 1

The static library probably contains several functions which are never used. When the linker links the library with the main executable, it sees that certain functions are never used (and that their addresses are never taken and stored in function pointers), it just throws away the code. It can also do this recursively: if function A() is never called, and A() calls B(), but B() is never otherwise called, it can remove the code for both A() and B(). On Linux, the same thing happens.