Compile each .c to assembly, assemble that to a .o object file, then link all the objects plus the C runtime into one executable.

* Each source file travels its own compile → assemble path to a .o; the linker fuses all objects plus the C runtime into the final executable. *

The compilation pipeline:

Key insight: Each .c file is compiled independently to its own .o file. The linker combines all .o files plus the C runtime library (CRT) into the final executable.

# View the full compilation process
$ gcc -v -O2 -Wall -g -o prog main.c swap.c

Tip: GCC is actually a "compiler driver" - it orchestrates calls to the preprocessor, compiler, assembler, and linker.

Go deeper:

• GCC — the compiler driver (Wikipedia) — how one gcc command chains preprocessor, compiler, assembler and linker.
• Ian Lance Taylor — Linkers, part 1 — start of a linker author's classic 20-part deep dive into what happens after compilation.