What is cc really doing - in a picture

• cc determines which compilation phases to perform based on the command-line options and the file name extensions provided.
• The compiler passes object files (with the filename suffix .o) and any unrecognized file names to the linker.
• The linker then determines whether files are object files or library files (often with the filename suffix .a).
• The linker combines all required symbols (e.g. your main() function from your .o file and the printf() function from C's standard library) to form the single executable program file.