makefiles continued:
- variable assignments and referencing
- multiple commands
- using '@' and '-' in front of cmd
- how make builds a total dependency tree

target: dependencies
	action
	action

- special variables:
	$?	all dependencies that are newer
	$<	first dependency that
	$@	target

- % rules
- defaults for various variables and file types

How Make builds a tree of dependecies
Make options
	-n show but don't do
	-k continue even if error
	-d debug/logging
	setting variables on command line
	make CC=gcc