The more one looks at old, nonexistent operating systems, the more one understands exactly why the popular operating systems we enjoy today are still in general use. Older operating systems share a large amount of similarities with current operating systems; the theory and patterns older operating systems incorporated are still in use in most modern-day operating systems. The programming languages used to create the system internals are again often the same. Even the high-level hardware architecture that many of these systems lived on (CPU, main memory, permanent memory) have stayed nearly constant. Yet despite all these similarities, many older operating systems are no longer used as much as they were in their heyday. These operating systems, once used by large swaths of the population, are now relegated to use by people running legacy systems for hobby or for profit. Three such operating systems, AtariOS, AmigaOS, and NewtonOS, exemplify all these characteristics. This paper will…