Since it was just posted, the xv6 ANSI C Unix source is nice and fairly compact. They even provide a nice PDF for you to take it with you: http://pdos.csail.mi

Since it was just posted, the xv6 ANSI C Unix source is nice and fairly compact. They even provide a nice PDF for you to take it with you: http://pdos.csail.mit.edu/6.828/2011/xv6/xv6-rev6.pdf http://pdos.csail.mit.edu/6.828/2011/xv6/xv6-rev6.pdf Also the low-level GLib core library is good: http://git.gnome.org/browse/glib/tree/glib http://git.gnome.org/browse/glib/tree/glib