When I go and make a C++ application I generally use libraries like SDL or WxWidgets and so on. But if I were to make a library would I need to use a library to make a library? Or can I make the entire library out of core C++ code, is this even possible?
My point is that there must be a point were a library has nothing to base itself on and so the only things it can use are core C++.
Am I right with this theory? If not, how are low-level libraries really made?
(I know this is a broad question, but I am a very curious person that needs answers and this is something that has bothered me.)
Low level libraries access hardware and system resources through libraries provided by the operating system. The operating system itself and the drivers loaded by it use assembly and reads/writes of predefined memory addresses to modify CPU state and communicate with hardware.
A library that only depends on C++ can only be a utility library as any communication with the hardware or user would involve either assembly or an additional library. An example for a pure C++ library without dependencies would be a math library, as it doesn't require I/O or hardware access.