| The study of a modern operating system leads down many paths and requires that we consider a number of different challenges and their solutions. The HP-UX kernel is a multitasking, multiuser, multiprocessor, multithreaded, load-leveling, modular operating system with real-time scheduling extensions to list just the highlights. To support such capabilities requires many levels of design abstraction, data tables, and lists as well as a host of subsystems, drivers, and dynamic modules. In this chapter, we examine the basic organization of the kernel and its data structures, and we consider which are dependent on the underlying hardware platform (hardware dependent-layer, HDL) and which are independent (hardware-independent layer, HIL). Before addressing HP-UX-specific topics, let's stop and think about what an operating system really is. |
