UNITED PLANETS FEDERATION, Earth -- Compiler theory in a nutshell à la Star Trek.

Scotty: Captain, we din' can reference it!
Kirk: Analysis, Mr. Spock?
Spock: Captain, it doesn't appear in the symbol table.
Kirk: Then it's of external origin?
Spock: Affirmative.
Kirk: Mr. Sulu, go to pass two.
Sulu: Aye aye, sir, going to pass two.

And to think they make you study this for a whole semester. If you don't get it you need to attend Compilers 101 for a full semester.