The concept of the operating system
System (Greek systema - an integer composed of parts, association) - a set of interrelated, regularly interacting objects that form a certain integrity for the performance of a single goal, of any functions and tasks.>
Computer system consists of devices (internal and peripheral) and programs that interact with, perform information processing processes on one or several computers. It can include various subsystems and enter as a subsystem into a larger system. Part of the software, responsible for the readiness of the computer system to work, forms an operating system in the general computer system.
Operating system (OS) - a set of programs that ensure the functioning of the computer and the user's work with resources.
Without the operating system, the user's access to the hardware and applications of the computer, as well as access to it via the network from another computer would not be possible (Figure 4.2).
Fig. 4.2. User interaction with a personal computer
Resource - any item required by the operating system, program and user: a device in the computer and network (disk, printer, memory), as well as system programs accessed by application programs. The term is used in such combinations as network, information, hardware, system resources.
The operating system provides the execution of applications, the allocation of resources of the computer system, input, output, data storage, data management, provides an interface (means of interaction) with the user and other computers, and issues messages.
The kernel of the operating system - its main part - is loaded into the RAM after turning on the computer
ter at runtime and manages the entire operating system, memory, execution of application programs, their interaction with hardware, determines the order and time of operation of various programs with the processor, processes failures of hardware and programs.
The other part of the operating system is loaded into memory as necessary and performs tasks of a higher level - provides the user interface with the application programs Application Program Interface, API.
Operating system functions:
• ensuring the automatic loading of the OS kernel into the main memory in accordance with the program code in the special (system) area of the disk;
• Organization of a file system for storing data on a disk, providing access to them and processing capabilities;
• loading programs into main memory and execution control.
Most modern operating systems multitask - control the distribution of computer resources between several applications (applications, tasks) so that:
• Multiple applications can work simultaneously, share resources;
• Applications can communicate with each other.
When several programs are open (for example, a text editor, a web browser, a music CD player), the computer system operates in multitasking mode: allocates CPU time, memory, executes commands, sends messages to each application or user about the state, possible errors and failures. The central processor quickly switches from executing one program to another, which creates the impression of simultaneously executing programs that actually run alternately. In multiprocessor systems or a multi-core processor, programs are actually executed in parallel.
The operating system allocates each application program part of the RAM, the programs share other hardware resources: hard disk, printer, remote access to the network.
Multitasking does not mean that you can successfully open an unlimited number of tasks. The more tasks are open, the slower the system works, it is more difficult to allocate free space in memory, divide device resources or install a queue on them. Sometimes multitasking is impossible: some programs and computer games require exclusive access to resources, cutting off other applications.
In multi-tasking operating systems, file locking works - a mechanism that prohibits several tasks from accessing one file at a time. A user attempting to open or edit a file already opened by another user or program receives a message about the inability to perform this task.
The operating system and programs can create a buffer in the main memory, or simply a buffer, - a protected area of temporary, unchanged data storage for copying and moving between windows of documents, programs or between the program and the I/O modules. The buffer is part of the RAM that is protected by the operating system because it stores the copied fragment, but some programs can accumulate several fragments in the buffer. The graphical interface provides the ability to graphically select and transfer data between the folder windows (dragging the file) and applications (for example, a chart from Excel, a picture from a website can be inserted into a Word document).
Virtual memory - the areas of RAM and external memory (on the hard disk) that the operating system creates to run several large programs on the computer, process data larger than the capacity actually (physically ) of the installed RAM.
When several large programs are launched simultaneously, large documents and graphics are edited, the operating system organizes additional large-scale virtual memory on the hard disk. For it, a special paging file is created on the disk for temporary storage of a part of the data, pending their transfer to the physical RAM as requested by the processor. The data, which is not in demand in the near future, is sent to the swap file.
Modern computers have 1 GB of RAM and higher, a paging file on the disk requires a few gigabytes of free space. If the space is not enough and the operating system overloads disk swelled file paging virtual memory, the number of calls to the hard disk increases, the work is slowed down, the system is unstable. It is recommended, without waiting for a failure, sometimes to forcely save the document being processed, and in the graphical editor use the Clear command from the history's " commands, restart the operating system.
If the programs are properly terminated, the operating system deletes the temporary files from the hard disk, but in the event of a crash, system hangs, and crashes on the disk, fragments of files may remain.
Device Driver - A program that allows a particular device, such as a modem, mouse, monitor, to interact with the operating system. The operating system allows itself an "abstraction from hardware and controls some virtual device & quot ;, using a standard set of instructions. It is the driver that translates these commands into a manufacturer-defined device.
Drivers of devices manufactured by different companies and included in the list of acceptable equipment are contained on the installation CD of the operating system. The installation of the operating system is accompanied by the installation and configuration of the drivers of all devices connected to the computer or the driver is suggested to be installed from the CD-ROM supplied with the device to be purchased.
On older operating systems, the user had to configure the system himself - specify which device was installed, determine its settings, and work with other devices.
In modern operating systems, there is a set of Plug and Play rules ( English - enabled and working) that allow you to automatically detect devices, recognize and configure them during the installation. Operating system, after discovering a new printer or modem, installs the driver that serves the device.
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