.a is an archive of code: compiled but not linked. You would link statically with it during your program's final link step.
.lib can be either the same as .a, or a magical so-called "import library": a thin placeholder which causes you to require a .dll at runtime.
Винда минимум раз в 2 недели ставит обновления и перезагружается.
Это начинает раздражать.