DEVELOPMENTS LEADING TO MODERN OPERATING SYSTEMS
The modern operating systems respond to new developments in hardware, new applications, and new security threats. Among the key hardware drivers are multiprocessor systems, greatly increased processor speed, high-speed network, increasing size and variety of memory storage devices. With respect to security, Internet access to computers has greatly increased the potential threat and increasingly sophisticated attacks, such as viruses, worms etc, have had a profound impact on OS design.
A wide range of different approaches and design elements has been tried in both experimental and commercial operating systems, but much of the work
fits into the following categories:
•Microkernel architecture : A microkernel architecture assigns only a few essential functions to the kernel, including address spaces, interprocess communication (IPC), and basic scheduling. •Multithreading : Multithreading is a technique in which a process, executing an application, is divided into threads that can run concurrently. We can make the following distinction: 1) Thread , 2) Process •Symmetric multiprocessing : Symmetric multiprocessing (SMP) is a term that refers to a computer hardware architecture and also to the OS behavior that exploits that architecture. SMP has a number of potential advantages over uniprocessor architecture, including the following: 1) Performance , 2) Availability , 3) Incremental growth , 4) Scaling.
•Distributed operating system : A distributed operating system provides the illusion of a single main memory space and a single secondary memory space, plus other unified access facilities, such as a distributed file system.
•Object-oriented design : Object-oriented design lends discipline to the process of adding modular extensions to a small kernel. At the OS level, an object-based structure enables programmers to customize an OS without disrupting system integrity.
