The drive-thru windows and super-sized meals of yesterday are yielding to the self-service kiosks and lighter, snackier diets of today as fast-food chains fight to survive. A study of restaurants throughout the years reveals some big changes not only in what they look like, but what they serve. What will the fast-food future hold? Taco Bell's futuristic new concept, set to debut next year, may give us a sneak peek.
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