An operating system (OS) is a set of interconnected system programs to organize the interaction of the user with the computer and the execution of all other programs. OSs are part of the system software and are the main part of it. Operating systems: MS DOS 7.0, Windows Vista Business, Windows 2008 Server, OS/2, UNIX, Linux.
The main functions of OS:
Management of computer devices (resources), i.e. coordinated operation of all PC hardware: standardized access to peripherals, management of RAM, etc.
process management, i.e. program execution and their interaction with computer devices.
management of access to data on non-volatile media (such as a hard disk, CD, etc.), usually with the help of a file system.
file structure maintenance.
User interface, i.e., dialog with the user.
Additional functions:
parallel or pseudo-parallel execution of tasks (multitasking).
interaction between processes: data exchange and mutual synchronization.
protection of the system itself, user data and programs from malicious actions of users or applications.
differentiation of access rights and multi-user mode (authentication and authorization).
Operating system composition
In general, the operating system consists of the following modules:
A software module that manages the file system.
The command processor, which executes the user’s commands.
The device drivers.
The program modules that provide a graphical user interface.
Service programs.
Help system.
Command processor – a special program that requests commands from the user and executes them (program interpreter).
The command processor is responsible for loading applications and managing the information flow between applications.
To simplify the user experience, modern operating systems include program modules that provide a graphical user interface.
The process of computer operation in a certain sense is reduced to the exchange of files between devices. The operating system has a program module that controls the file system.
Service programs allow you to serve disks (check, compress, defragment, etc.), perform operations with files (copying, renaming, etc.), work in computer networks.
For your convenience, the operating system includes a help system, which gives you all the information you need on the operation of the OS as a whole, and on the operation of its individual modules.
The most common approach to the structuring of the operating system is to divide all its modules into two groups:
The kernel are the modules that perform the main functions of the operating system.
Auxiliary modules that perform auxiliary functions of the operating system. One of the defining properties of the kernel is to work in privileged mode.
The kernel modules perform the following basic OS functions: Process Control, Interrupt System Control, Memory Management, I/O Device Management, Functions that solve intra-system tasks of computing process organization: context switching, page loading/unloading, interrupt handling. These functions are not available to applications. Functions that serve to support applications by creating for them what is called an application programming environment.
Applications can call the kernel with requests – system calls – to do certain things: open and read a file, display graphic information, get the system time, etc. The kernel functions which can be invoked by an application form the Application programming interface (API).
Kernel is a Windows module, which provides low-level functions for working with files and managing memory and processes. This module provides a service for 16-bit and 32-bit applications.
GDI (Graphics Device Interface) – A Windows module that provides graphics functions for color, fonts and graphics primitives for displays and printers.
User – A Windows module that is a window manager and creates and manages windows, dialog boxes, buttons, and other user interface elements displayed on the screen.
The kernel is the driving force behind all computational processes in a computer system, and the failure of the kernel is tantamount to the collapse of the entire system, without it the OS is completely inoperable and will not be able to perform any of its functions. Therefore, the developers of the operating system pay special attention to the reliability of the kernel codes, as a result, the process of debugging them can stretch for many months.
Usually the kernel is designed as a program module of some special format that differs from the format of the user’s applications.
OS auxiliary modules perform auxiliary functions of the OS (useful, but less obligatory than kernel functions).