Operating Systems

(https://en.wikipedia.org)

An operating system (OS) is a collection of software that manages computer hardware resources and provides common services for computer programs. The operating system is a vital component of the system software in a computer system. Application programs usually require an operating system to function.

Time-sharing operating systems schedule tasks for efficient use of the system and may also include accounting for cost allocation of processor time, mass storage, printing, and other resources.

For hardware functions such as input and output and memory allocation, the operating system acts as an intermediary between programs and the computer hardware, although the application code is usually executed directly by the hardware and will frequently make a system call to an OS function or be interrupted by it. Operating systems can be found on almost any device that contains a computer – from cellular phones and video game consoles to supercomputers and web servers.

A real-time operating system is a multitasking operating system that aims at executing real-time applications. Real-time operating systems often use specialized scheduling algorithms so that they can achieve a deterministic nature of behavior. The main objective of real-time operating systems is their quick and predictable response to events.

Early computers were built to perform a series of single tasks, like a calculator. Operating systems did not exist in their modern and more complex forms until the early 1960s. Basic operating system features were developed in the 1950s, such as resident monitor functions that could automatically run different programs in succession to speed up processing. Hardware features were added that enabled use of runtime libraries, interrupts, and parallel processing. When personal computers became popular in the 1980s, operating systems were made for them similar in concept to those used on larger computers.

The use of virtual memory addressing (such as paging or segmentation) means that the kernel can choose what memory each program may use at any given time, allowing the operating system to use the same memory locations for multiple tasks. If a program tries to access memory that isn't in its current range of accessible memory, but nonetheless has been allocated to it, the kernel will be interrupted in the same way as it would if the program were to exceed its allocated memory.

Multitasking refers to the running of multiple independent computer programs on the same computer; giving the appearance that it is performing the tasks at the same time. Since most computers can do at most one or two things at one time, this is generally done via time-sharing, which means that each program uses a share of the computer's time to execute.

Access to data stored on disks is a central feature of all operating systems. Computers store data on disks using files, which are structured in specific ways in order to allow for faster access, higher reliability, and to make better use out of the drive's available space. The specific way in which files are stored on a disk is called a file system, and enables files to have names and attributes. It also allows them to be stored in a hierarchy of directories or folders arranged in a directory tree.

Слова для сдачи наизусть:

1. software - программное обеспечение; программные средства

2. time-sharing - использование эвм в режиме разделения времени

3. cost allocation - распределение расходов

4. mass storage - запоминающее устройство

5. input and output - ввод и вывод

6. interm e diary - посредник; промежуточное звено

7. computer hardware - компьютерное аппаратное обеспечение

8. to e xecute application code - создать код применения

9. c e llular phone - сотовый телефон

10. video game console - игровая видео приставка

11. real-time operating system - операционная система, управляющая обработкой данных в

реальном времени

12. pred i ctable resp o nse - предсказуемый ответ

13. to perf o rm a task - выполнять задачу

14. runtime libraries - библиотеки рабочих программ

15. paging - разбивка памяти ЭВМ на " страницы"

16. kernel - ядро

17. accessible memory - доступная память

18. multitasking - многозадачный режим работы; многозадачность

19. reliability - надёжность

20. directory tree - древовидная система справочников