Step 7 of 9: Understanding Makefiles (cont.)

A makefile can contain four types of lines, each of which are described below.

1. Comment Lines -- All lines in the makefile that begin with the # sign are comments. These lines are provided simply to give the user some useful information.

2. Macro Definitions -- Macro definitions are the lines that define the name of the macro, and then give its meaning. For example, CC = cc means that CC is the macro name, and cc is its definition. To dereference a macro you simply place it inside parenthesis, and preceed it with the $ sign, for example $(CC). This is the form the macro takes when used in the target and action lines. 

3. Target Lines -- The target lines list the goal, and the dependencies needed to obtain the goal. The goal is the executable file that you wish to create. The dependencies, either a file or another goal, follow a colon and tell make what this goal needs to be current. If any modifications are made to a goal's dependencies then that goal is no longer current, and the actions given on the action line should be performed.

                                                           example: example.o

This line will make the executable file example dependent on the object file example.o.

4. Action Lines -- The action lines tell make how to create the dependencies, and therefore the goal. The macros given on this line are expanded and used to compile the source code into the executable name given on the target line. The action lines must begin with a tab,not spaces, and must come directly under a target line (ie. no newline characters).

THE STEPS FOR COMPILATION AND EXECUTION ARE EXPLAINED IN STEP 8.