A particular combination of CPU and OS is called a platform.

Each computer system can only execute code written in its own low level, platform specific language.

A compiler translates high level code into platform-specific machine language.

Java works somewhat differently.

A very important software development practice is code reuse.

Carefully designed software components that can be reused are thoroughly tested and documented and then placed in code libraries.

To reuse a library class you need to #include its header file in your source code.

After compilation, a linker is responsible for making sure that all symbols that are not defined in the program source code are linked to compiled definitions in the #included libraries.

The compiled library code does not need to be incorporated into the executable file because it can be dynamically linked at runtime.

This results in smaller executable files and more efficient use of memory.

A lib is a file that contains several object files.

Each lib generally contains some kind of index of symbols to facilitate the linking process.

C++ Libraries can be packaged in a few different ways.

To summarize, the variety of ways that C++ code can be organized and packaged facilitates code sharing and reuse.