Show understanding of program libraries

What is a Program Library?

Think of a library like a real‑world book library 📚. Instead of books, it holds reusable pieces of code – functions, classes, and resources that many programs can use. This saves time and keeps code tidy.

Types of Libraries

• Static libraries (.a or .lib) – copied into the program at compile time.
• Dynamic / Shared libraries (.so, .dll, .dylib) – loaded at run‑time and shared by many programs.
• Header files (.h, .hpp) – contain declarations so the compiler knows what functions exist.

How Libraries Work (Static vs Dynamic)

Linking Process Explained

1. Compiler reads .c files and .h headers.
2. Assembler turns code into object files .o.
3. Linker resolves symbols:
   • Static: copies library object files into the final executable.
   • Dynamic: records references to shared libraries.
4. Result: an executable that can run on the target OS.

Benefits of Using Libraries

• ?? Reusability – write once, use many times.
• ?? Modularity – separate concerns into different files.
• ?? Maintainability – update library, all programs benefit.
• ?? Space optimisation – shared libraries reduce memory footprint.

Exam Tips

• Explain the difference between static and dynamic linking using a real‑world analogy.
• Show the linking steps in order – use a numbered list or table.
• Remember that header files only contain declarations; the actual code lives in the library.
• Use the symbol + to show that static libraries are merged into the executable.
• When asked about memory usage, compare static vs dynamic with a simple diagram or table.