Modern Operating System

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1. The operating system is the most important program that runs on a computer. Every general-purpose computer must have an operating system to run other programs. Operating systems perform basic tasks, such as recognizing inputfrom the keyboard, sending output to the display screen, keeping track of filesand directories on the disk, and controlling peripheral devices such as disk drives and printers. 2. The kernel is a program that constitutes the central core of a computer operating system. It has complete control over everything that occurs in the system. A kernel can be contrasted with a shell (such as bash, csh or ksh in Unix-like operating systems), which is the outermost part of an operating system and a program that interacts with user commands. The kernel itself does not interact directly with the user, but rather interacts with the shell and other programs as well as with the hardware devices on the system, including the processor (also called the central processing unit or CPU), memory and disk drives. The kernel is the first part of the operating system to load into memory during booting and it remains there for the entire duration of the computer session because its services are required continuously. Thus it is important for it to be as small as possible while still providing all the essential services needed by the other parts of the operating system and by the various application programs. 3. Virtual memory is a feature of an operating system that enables a process to use a memory (RAM) address space that is independent of other processes running in the same system, and use a space that is larger than the actual amount of RAM present, temporarily relegating some contents from RAM to a disk, with little or no overhead. 4. Paging is a method of writing data to, and reading it from, secondary storage for use inprimary storage, also known as main memory. Paging plays a role in memory management for a computer's OS (operating system). In a memory management system that takes advantage of paging, the OS reads data from secondary storage in blocks called pages, all of which have identical size. The physical region of memory containing a single page is called a frame. When paging is used, a frame does not have to comprise a single physically contiguous region in secondary storage. This approach offers an advantage over earlier memory management methods, because it facilitates more efficient and faster use of storage. 5.

6. A file that contains graphics, animation, audio or video. A multimedia "file" typically refers to all file formats other than text files. However, the term "multimedia" by itself embraces all forms of information and therefore would have to include text. 7. In computing, input/output or I/O is the communication between an information processing system (such as a computer) and the outside world, possibly a human or another information processing system. Inputs are the signals or data received by the system, and outputs are the signals or data sent from it. The term can also be used as part of an action; to "perform I/O" is to perform an input or output operation. I/O devices are used by a person (or other system) to communicate with a computer. For instance, a keyboard or a mouse may be an input device for a computer, while monitors and printers are considered output devices for a computer. Devices for communication between computers, such as modems and network cards, typically serve for both input and output. 8. "Authentication" means establishing the true identity of a network node or user. This can be accomplished through many different protocols or procedures. A username/password request can be considered a form of authentication. 9. A multiprocessor is a tightly coupled computer system having two or more processing units (Multiple Processors) each sharing main memory and peripherals, in order to simultaneously process...
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