Let's start at the very beginning, a very good place to start,

When you're learning to sing, its Do, Re, Mi;
When you're learning to code, its G, D, B.

(background) G, D, B.

The first three letters just happen to be, G, D, B.

(background) G, D, B.

(Chorus)

G!,

GNU!, it's Stallman's hope,

D,

debug that rotten code,

B,

a break I set myself.

Run,

a far, far way to go.

Print,

to see what you have done,

Set,

a patch that follows print.

Quit,

and recompile your code - - -

That will bring it back to G,
                              D,
                                 B,
                                    <link>

(Resume from the Chorus)