An operating system (OS) is the software responsible for controlling and managing hardware and basic system operations, as well as running application software such as word processing programs, Web browsers, and many others. In general, the operating system is the first layer of software loaded into memory when a computer starts up. All other software that gets loaded after it depends on the operating system to provide various common core services, such as disk access, memory management, process scheduling, and user interfaces. As operating systems evolve, ever more services are expected to be common core. These days, an OS may be required to provide network and Internet connectivity and also to protect the computer's other software from damage by malicious programs, such as viruses. Operating systems in widespread use on personal computers (PC) have consolidated into two families: the Microsoft Windows family and the Unix-like family. Mainframe computers and embedded systems use a variety of different operating systems, many with no direct connection to Windows or Unix.
Building Operating Systems is much about studying existing systems, knowing common problems, knowing what other people did, and figuring out if their ideas can be applied to a given new problem. These long-lasting principles - as opposed to implementation details and user interfaces of today's systems/software - is what this lecture is about.