While the gcc command-line options provide a great deal of flexibility when compiling programs, things quickly become unmanageable when the number of source files exceeds what you can conveniently type in a few seconds.

The make utility can be thought of as a companion to the compiler infrastructure (preprocessor, compiler, assembler, and linker) that allows the build rules for large projects to be explicitly encoded in Makefiles. A Makefile typically consists of common definitions, (such as, which compiler to use), and a set of rules. Each rule has a target, such as the file that is to be built, and can be followed by a list of dependencies and a sequence of steps to perform in order to build that target. In addition, make has quite a few common rules built into it.

You will not have to write your own Makefiles for this course, but you will have to use and possibly modify some for all of our remaining assignments. The Makefile is always human-readable, so feel free to open them up and look around.

To build the XINU operating system, perform the following steps:

• Change directory into the top level produced by the tar-ball, called xinu-hw3 for the first kernel assignment.
• Change directory into the subdirectory "compile". This directory contains the XINU project Makefile, and is where the compiled kernel image file will go.
• Execute the the following command:
     make clean
  By standard convention, almost all Makefiles include a target called "clean" that removes everything except the source code. The tar-ball you unpacked already should be clean, but it never hurts to make sure that you are starting from a clean slate. You may find yourself using this command often.
• Execute the the following command:
     make

This should produce about a page of output as each source file is compiled, and the resulting object files are linked together to form the operating system, a simple set of library functions, and the boot loader. If all goes as it should, you should find the directory full of .o files from all of the source code in the other subdirectories, and most importantly, a newly compiled operating system image called "xinu.boot."

For more information on make, please see the UNIX man pages.