Edited169 by Evolving Ideas Jeetendra Pande Computing, Communication and Networking Nihar Ranjan Pande Deep Chandra Joshi Publish by Global Vision Publishing House Advanced Architecture Based OS Neeraj Sharma1, Rajat Goel2 and Rajeev Kumar3 ABSTRACT The modern operating systems are made with the advanced architecture, which made the efficient utilization, highly scalable, and high availability of the resources and the services. The earliest operating systems were developed for mainframe computer architectures in the 1960s. The enormous investment in software for these systems caused most of the original computer manufacturers to continue to develop hardware and operating systems that are compatible with those early operating systems. Those early systems pioneered many of the features of modern operating systems. Modern mainframes typically also run Linux or Unix variants. A “Datacenter” variant of Windows Server 2003 is also available for some mainframe systems. INTRODUCTION Basically an operating system is software which enable the user to interact with hardware also provide an interface to the user to run an application. The core basic architecture was design by considering certain issues in the existing hardware they are: Processors are executing the instructions serially one by one at a time; there is a need of such an architecture, which can handle the multiple users simultaneously; hardware was too costly so people use to buy the computers on the leased basis. That made to a need for the time-sharing system. There is need for a communicator who can interact with the system and can manage the hardware resources efficiently and optimistically. There is the core component of the system that is responsible for the all there issues named as kernel. KERNEL AND ITS TYPES Kernel is the core of the operating system, which manages the resources and users. The kernel’s primary purpose is to manage the computer’s resources and allow other programs to run and use these 1. Associate Proffesor JP Institute of Engineering & Technology, Meerut. 2. Lecturer Translam Institute of Technology & Management, Meerut. 3. Lecturer Translam Institute of Technology & Management, Meerut. 170 Neeraj Sharma, Rajat Goel and Rajeev Kumar resources. Typically, the resources consist of: the CPU (frequently called the processor), the most central part of a computer system, responsible for running or executing programs on it. The kernel takes responsibility for deciding at any time which of the many running programs should be allocated to the processor or processors (each of which can usually run only one program at a time). There are various types of the kernel: a) Micro kernel; b) Monolithic Kernel; c) Nano Kernel; d) Hybrid Kernel. A microkernel is a minimal computer operating system kernel which, in its purest form, provides no operating-system services at all, only the mechanisms needed to implement such services, such as low- level address space management, thread management, and inter-process communication (IPC). The microkernel is the only part of the system executing in a kernel mode. The actual operating-system services are provided by user-mode servers. These include device drivers, protocol stacks, file systems and user- interface code. A monolithic kernel is a kernel architecture where the entire kernel is run in kernel space in supervisor mode. In common with other architectures (microkernel, hybrid kernels), the kernel defines a high-level virtual interface over computer hardware, with a set of primitives or system calls to implement operating system services such as process management, concurrency, and memory management in one or more modules. Courtesy: Wikipedia.org:: Graphical Overview of Monolithic Kernel Fig. 1 A nanokernel or picokernel is a very minimalist operating system kernel. The nanokernel represents the closest hardware abstraction layer of the operating system by interfacing the CPU, managing interrupts and interacting with the MMU. The interrupt management and MMU interface are not necessarily part of a nanokernel; however, on most architectures these components are directly connected to the CPU, therefore, it often makes sense to integrate these interfaces into the kernel. Hybrid kernel is a kernel architecture based on combining aspects of microkernel and monolithic kernel architectures used in computer operating systems. Advanced Architecture Based OS 171 Fig. 2 Modern kernel architecture comes with the hierarchical protection domains are much less flexible, as is the case with every kernel with a hierarchical structure assumed as global design criterion. In the case of protection it is not possible to assign different privileges to processes that are at the same privileged level, and therefore is not possible to satisfy Denning’s four principles for fault tolerance (particularly the Principle of least privilege). Hierarchical protection domains also have a majaor performance drawback, since interaction between different levels of protection, when a process has to manipulate a data structure both in ‘user mode’ and ‘supervisor mode’, always requires message copying (transmission by value). A kernel based on capabilities, however, is more flexible in assigning privileges, can satisfy Denning’s fault tolerance principles, and typically doesn’t suffer from the performance issues of copy by value. Ring 3 least privilege Ring 2 Ring 1 Ring 0 Kernel Device drivers Most Privilege Device drivers Applications Fig. 3 Based on the application and purpose there are different kernel architectures and based on them there are various types of operating systems: Disk Operating System [DOS] Many vendors had introduces with the DOS operating system for the PC’s and mini computer. It includes basic disk management and data retrival commands, along with some editing commands. File 172 Neeraj Sharma, Rajat Goel and Rajeev Kumar system vary from vendor to vendor basically. MS-DOS and PC-DOS were using FAT16 as their file system. Later MS-DOS 7.1 added a support for FAT32. DOS is having capability to swap its kernel with the application. It is 16 bit operating system, programmed in assembly language. As every application is having its own starting point, the linker and loader in the kernel loads at its entry point, and kernel swaps its memory loaction to other location. Initially, DOS was design for PC’s and supported only disk level operation later on it supported network and FAT32 file system. Following are the list of DOS distributed by different vendors for different architecture: • CP/M – Control Program/Monitor developed by Digital Research Inc; • MP/M –Multi user version of CP/M, developed by Digital Research Inc; • DR-DOS –developed by Digital Research Inc; • OpenDOS – by Free Software Foundation; • Apple DOS – developed by Apple; • DOS/360 – developed by IBM; • PC-DOS/386 - by IBM; • FreeDOS32 - by GNU. Network Operating System (NOS) A network operating system (NOS) is a computer operating system that is designed primarily to support workstation, personal computer, and, in some instances, older terminal that are connected on a local area network (LAN). Artisoft’s, LANtastic, Banyan VINES, Novell’s NetWare, and Microsoft’s LAN Manager are examples of network operating systems. In addition, some multi-purpose operating systems, such as Windows NT and Digital’s OpenVMS come with capabilities that enable them to be described as a network operating system. A network operating system provides printer sharing, common file system and database sharing, application sharing, and the ability to manage a network name directory, etc. There is NOS oprating system that includes Novel Netware, Windows NT and 2000, Solaris, IBM OS/2, UNIX, etc. While Cisco IOS is called as Internet Operating System. Some of the features of network operating system are: • Provide basic operating system features such as support for processors, protocols, automatic hardware detection and support multi-processing of applications; • Security features such as authentication, authorization, logon restrictions and access control; • Provide name and directory services; • Provide file, print, web services, back-up and replication services; • Support Internetworking such as routing and WAN ports; • User management and support for logon and logoff, remote access, system management, administration and auditing tools with graphic interfaces; • Clustering capabilities, fault tolerant and high availability systems. Embedded Operating System Embedded systems use a variety of dedicated operating systems. In some cases, the “operating system” software is directly linked to the application to produce a monolithic special-purpose program. In Advanced Architecture Based OS 173 the simplest embedded systems, there is no distinction between the OS and the application. Embedded systems that have certain time requirements are known as Real-time operating systems. There are many vendors who introduce with their distributions: • Open BSD; • Embedded Linux; • Free RTOS; • LynxOS RTOS; • NetBSD; • Windows XP Embedded; • Windows CE; • Symbian OS. WINDOWS NT ARCHITECTURE The architecture of Windows NT is highly modular and consists of two main layers: a user mode and a kernel mode. Programs and subsystems in user mode are limited in terms of what system resources they have access to, while the kernel mode has unrestricted access to the system memory and external devices. The kernels of the operating systems in this line are all known as hybrid kernel, although this term is disputed, with the claim