Operating system characteristics. Informatics - Operating system (OS) - The main tasks of the OS - User interface - Characteristics, shells Purpose general characteristics of operating systems

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OPERATING SYSTEM (OS) WINDOWS

GENERAL CHARACTERISTIC OF THE WINDOWS OS FAMILY

Windows family OS. Major versions of Windows

OS of the Windows family are software products of Microsoft corporation and are a set of programs designed for effective use of all computer tools in the process of solving user problems and organizing interaction between the user and the computer. OS ensure the joint functioning of all computer devices and provide the user with access to its resources. Microsoft operating systems, like other manufacturers' operating systems, can be classified according to a number of characteristics:

  • the main purpose;
  • the number of concurrent users;
  • the number of tasks simultaneously running under the OS;
  • the way of using hardware and software;
  • type of user interface;
  • system requirements for hardware;
  • the file system used;
  • language version;
  • ? bit width MP, etc.

Let's classify Microsoft's operating systems according to the most important criteria.

According to its main purpose, the OS of the Windows family can be conditionally divided into three groups, or, as they are also called, lines: 9x - line, NT - line and CE - line. Some authors distinguish another group (16 - Bit - line), which include Windows 1.0 (1985), Windows 2.0 (1987), Windows 2.1 (1987), Windows 3.0 (1990), Windows 3.1 (1992), Windows 3.11 (1992). However, these versions were not full-fledged operating systems, but were operating shells for working with MS DOS (Microsoft Disk Operating System, which was developed by Microsoft in 1981). The main purpose of these versions was to implement the graphical interface of MS DOS.

The first group (9x - line) includes OS versions: Windows 95 (1995), Windows 98 (1998), Windows ME (Millennium Edition, 2000). This OS group was intended for installation on personal computers with 32-bit microprocessors and operating in local (autonomous) mode. Currently, this OS group is practically not used and is not supported by the developer.

The second group (NT - line, New Technology - new technology) is the most numerous, it includes the following versions: Windows NT 3.1 (1993), Windows NT 3.5 (1994), Windows NT 3.51 (1995), Windows NT 4.0 (1996), Windows NT 5.0 (Windows 2000, 2000), Windows NT 5.1 (WindowsXP, 2001 n). Windows NT 5.2 (Windows Server 2003, 2003), Windows NT 6.0 (Windows Vista 2006, 2006), Windows Home Server (2007), Windows Server 2008, Windows NT 6.1 (Windows 7, 2009) ... The operating systems of this group are fully 32-bit and do not need support from the MS DOS operating system. The main purpose of this group is to support the network mode of the computer. Currently, this OS group finds the greatest practical application and is supported by the developer, except for some earlier versions.

The third group (CE - line, CE - Compact Edition - compact edition) is intended for laptop computers. This group includes the following versions: Windows CE 1.0 (1997), Windows CE 2.0 (1998), Windows CE 3.0 (2000), Windows CE 4.0 (2002), Windows Mobile 2003 (2003). ), Windows Mobile 5.0 (2005), Windows Mobile 6.0 (2007).

By the number of concurrent users, single and multiuser operating systems are distinguished. Their main difference from each other is the availability of means of protection against unauthorized access. In multi-user operating systems, there are means to protect each user from unauthorized access by other users. Each user can enter (load) a multi-user OS under his own password, he is allocated his own segment of the main computer memory. An example of multiuser operating systems are versions of the first and second groups of the Windows family.

According to the number of simultaneously executed tasks, the OS is divided into single and multitasking. OS of the Windows family refers to preemptive multitasking. A user working with an OS of the Windows family can simultaneously perform several tasks in different windows, while the windows on the screen are assigned to different tasks. Windows family operating system runs in protected mode (protected mode), those. when using a microprocessor in multitasking mode, running programs do not interfere with each other.

By the way of using hardware and software, OS can be divided into network and local OS. The main versions of the second and third groups of the Windows family can be attributed to network operating systems, and the first group to local ones.

By the type of user interface, the OS can be divided into OSs that present the user with text and graphical interfaces. Windows operating systems present the user with a graphical interface.

Of the Windows versions listed above, the most demanded versions of Windows XP, Windows Vista and Windows 7 are currently in demand for installation on personal computers.

Let's give a brief description of these versions of Windows and describe the capabilities they provide to users.

Windows XP was released by Microsoft in October 2001 and is an evolution of Windows 2000 Professional. The name XP comes from the English eXPerience, which means experience. Microsoft has introduced three major editions (editions) of Windows XP: Windows XP Home Edition, Windows XP Professional Edition, and Windows XP 64-bit Edition. In addition to the main editions of Windows XP, there were additional ones, which include: Windows XP Media Center Edition (based on Windows XP Professional Edition and contains special multimedia applications), Windows XP Embedded (embedded component OS based on Windows XP Professional Edition, it is designed for use in various embedded systems: ATMs, medical devices, POS terminals, gaming machines, etc.), Windows Embedded for Point of Service (a specialized OS based on Windows XP Embedded, configured for service points, it is optimized for retail and service), etc. Next, we will focus on the main releases of Windows XP.

Windows XP Home Edition was designed for home PC users (installed on laptops). This release differs from the previous version of Windows 2000 with a new look and feel that makes it easier and more efficient to complete your daily tasks. The improved possibilities of working with digital images and music recordings both when working on a local personal computer and when exchanging them over the Internet have become available to users.

OS Windows XP Professional is a more powerful OS than previous OS versions due to the high level of scalability and reliability of the OS. It is intended mainly for corporate users. The scalability of this OS consists in support of RAM, which can be increased up to 4 GB, and support for increasing the power of the microprocessor (for example, installing two microprocessors).

Let's list the main features provided to the user of Windows XP Professional, which can also be interpreted

as distinctive features of this OS in comparison with previous versions of the Windows family:

  • improved user interface, improved design, including more rounded shapes and smoother colors;
  • relatively higher level of security, including the ability to encrypt folders and files to protect corporate information;
  • built-in support for high-performance multiprocessor systems;
  • the ability to quickly switch users, which allows you to temporarily interrupt the work of one user and log into the system as another user, while leaving the applications launched by the first user enabled;
  • convenience in performing various operations due to the wizards built into the OS (for example, "Desktop Cleaning Wizard", "Network Installation and Settings Wizard", "Shortcut Wizard", "Internet Connection Wizard", etc.);
  • OS recovery, which is designed to return the system to a certain previous state, as well as improve other methods of system recovery. So, when the last successful configuration is loaded, the previous set of drivers is also loaded, which in some cases makes it easy to restore the system in case of problems resulting from the installation of drivers, the ability to rollback drivers, i.e. reverting to previous versions of drivers (computer programs that ensure the functioning of computer peripherals) due to software failures, etc.;
  • more advanced system management functions from the command line;
  • support by the "Explorer" utility for digital graphic and audio formats;
  • Windows XP Professional includes technologies developed by Roxio that allow you to write data to optical discs without installing additional software;
  • The OS includes a Windows Media audio player that lets you play digital media, including music, videos, optical discs, and Internet radio;
  • OS Windows XP Professional can work with ZIP archives without installing additional software;
  • laptop support tools including DualView and OeagTure technologies. DualView technology (work with two monitors) allows you to display the "Desktop" of the computer on two monitors controlled by one video adapter. For example, in addition to the liquid crystal display, you can connect an external monitor to laptop computers. The use of this technology allows to increase the productivity of users and does not require additional microprocessors. OeagTure technology improves the clarity of text display on an LCD screen because it triples the horizontal resolution of displayed text on a computer screen, and also has a firewall for Internet connections, etc.

The developer must accompany any software product released to the market. During the maintenance process, noticed malfunctions in the program, errors, so-called holes in the protection system against unauthorized access, etc. are eliminated. Windows XP is no exception. During the maintenance of Windows XP, Microsoft Corporation also eliminated bugs in the OS and periodically released Service Packs for the OS. The purpose of these software packages was to address identified issues and add new capabilities.

The first Service Pack 1 (SP1) for Windows XP was released in September 2002. The most important innovations in the package were: support for the USB 2.0 interface, the introduction of a utility that allows you to select default programs for viewing e-mail, the implementation of the Java virtual machine (Java Virtual Machine, the Java virtual machine interprets and executes Java bytecode that is pre-generated from the Java source code by the Java compiler.Because Java virtual machines are available for many hardware and software platforms, Java can be viewed as both middleware and stand-alone platform), the Encrypting File System (EFS) now has the ability to use the Advanced Encryption Standard (AES) encryption algorithm - a symmetric block encryption algorithm with a block size of 128 bits and a key of 128/192/256 bits, adopted as an encryption standard by the US government in May 2002) with a 256-bit key, etc. Support for Windows XP Service Pack 1 ended in October 2006.

The second Service Pack 2 (SP2) (codenamed Springboard) was released in August 2004. The most important innovations in SP2: improved firewall (firewall - formed by transliteration of the English term firewall, which is equivalent to the term "firewall", is currently not the official borrowed word in Russian, the analogue of the English word firewall, is the German word brandmauer (firewall), which literally means a wall that separates adjacent buildings, preventing the spread of fire); master of support for Wi-Fi connections with the Internet and Bluetooth (English translation of the nickname of the Danish king Harald 1 Bluetooth (910-986), who united Denmark with Norway. His name was chosen as the name of the technology because originally Bluetooth was intended as a means of simple connections of computers and telecommunication devices), Bluetooth technology provides information exchange on a radio frequency in the 2.4-2.48 GHz range (license-free range) for short-range communication with a radius of 10-100 m between devices such as PDAs and ordinary personal computers, mobile phones, laptops, printers, digital cameras, etc.), as well as an improved version of the Internet Explorer browser (IE6, for example, the ability to block pop-up windows on the Internet). This service pack introduced significant security changes to the Windows XP operating system. So, the built-in firewall has undergone significant changes, which was renamed to Windows Firewall and was activated for all created connections by default. Security changes have affected both Outlook Express and IE. Windows XP Service Pack 2 includes Windows Security Center, which makes it easier to monitor the security of the system by monitoring and reminding the user to install or update the antivirus and its databases, activate the built-in or third-party firewall, update the operating system or change browser settings, etc. etc. Since July 2008, Microsoft has discontinued support for Windows XP SP2.

Service Pack 3 (final version) was released by Microsoft in April 2008. This package includes all updates released since Windows XP Service Pack 2 was released in 2004, as well as a number of other new items. These include Network Access Protection and a new activation model borrowed from Windows Vista, plus improved detection of so-called black hole routers and more. Windows XP SP3 is currently marketed in both OEM (Original Equipment Manufacturer) and Boxed (BOX) versions.

It is also important to note here that Microsoft ceased free support for Windows XP on April 14, 2009, and from that time on, Windows XP users cannot contact Microsoft for free technical support. Now they will have to use “extended support” services for this. all calls are paid. This support will continue until April 8, 2014.

Windows XP 64-bit Edition was developed specifically for workstations based on 64-bit Intel Itanium microprocessors. This OS provides support for additional memory, increases the speed of I / O operations, and expands the possibilities for calculating floating point variables. This OS is a powerful enough platform for technical and analytical development, as well as for financial and statistical analysis. This edition of Windows XP has been discontinued since 2005, after HP (Hewlett Packard, USA) discontinued development of workstations with Intel Itanium microprocessors. Support for this architecture remained in the server versions of the Windows operating system.

OS Windows Vista also belongs to the NT - line (NT - line, New Technology - a new technology focused on network operation) of operating systems of the Microsoft Windows NT family, and in particular, it is called Windows NT 6.0 in this line. It is mainly used on custom personal computers. Microsoft officially released Windows Vista on November 30, 2006 to corporate customers, and on January 30, 2007, it began selling the OS in retail. Microsoft Corporation presented several editions (variants, editions) of Windows Vista. Let's consider the main ones:

  • Windows Vista Starter is the most affordable and affordable option for entry-level users. The basic set of features of Windows Vista Starter is limited compared to other editions, but most importantly, it remains compatible with all modern applications and devices. In fact, this is an operating system for beginners who take the first steps in mastering a personal computer and do not want to overpay for software when buying their first computer;
  • Windows Vista Home Basic is also a fairly simple and affordable version of Windows Vista, designed primarily for home users. It has all the main characteristics of a next-generation OS: security, support for extended parental controls, a basic user interface, new search and data organizing functions, and improved networking. At the hardware level, this is support for one microprocessor (with unlimited number of cores) with 8 GB of maximum RAM for the Amd64 platform (64-bit) and 4 GB for the x86 platform (32-bit);

OC Windows Vista Home Premium is the main Windows Vista option for home users of desktop and mobile personal computers. In addition to the capabilities provided by Windows Vista Home Basic, it supports the Windows Aero 3-D user interface, Windows Media Center, and a number of additional multimedia capabilities (such as editing and burning DVDs). At the hardware level, Windows Vista Home Premium supports up to two microprocessors with 16 GB of maximum RAM, HDTV (High Definition TV is one of the trends in the development of television in the world, its Russian name is high-definition television, which allows you to watch TV programs, films with resolution 1920 x 1080 pixels, unlike conventional television, which uses 720 by 576 pixels), video DVD recording, support for touch screens, automatic backup. However, this option lacks the ability to join the domain and the editor of group and local policies, there is no support for EFS;

Windows Vista Business is the primary hardware platform for enterprise-class desktop and mobile personal computers. This version of the OS is suitable for small, medium and large businesses, contains all the functions of Windows Vista Home Basic (except for a number of entertainment) and has a number of specific features. For example, Windows Vista Business supports Windows Aero, Group Policy, file system encryption, fax and scanner support, and more. At the hardware level, Windows Vista Business supports up to two processors, Windows Aero, Group Policy, and EFS. However, in this version, the multimedia part is reduced and there are no entertainment applications;

Windows Vista Enterprise is an enhanced version of Vista for corporate personal computers and laptops. In addition to Vista Business capabilities, this option includes Windows BitLocker Drive Encryption, supports all existing interface languages, Virtual PC Express, and the Subsystem for UNIX-Based Applications (SUA). this OS version is suitable for large enterprises and organizations with complex infrastructure. At the hardware level, it is similar to the previous version of the OS;

Windows Vista Ultimate is an option that includes all the features of Windows Vista Home Premium and Windows Vista Enterprise. In this version, the multimedia part is well developed, support for animated desktop wallpaper is implemented, and it is also possible to change the language of the operating system user interface if desired.

Microsoft also accompanies the Windows Vista operating system that has entered the market. This support consists in regular updating of the OS, eliminating the identified problems and adding new OS features.

The first Service Pack 1 (SP1) for Windows Vista was released on April 15, 2008. This service pack allowed for faster file copying to local computers (25% faster), faster processing of high-resolution images. In addition, SP1 includes add-ons that improve the operating system's compatibility with new video adapters, some types of monitors and printers. The service pack also includes fixes that reduce wake-up time, improve IE 7.0 performance, and improve laptop power management. Also included in SP1 are all previously released patches and patches. Before installing SP1, Windows Update checks the computer for problematic components and, if found, postpones the installation.

Service Pack 2 (SP2) is the second most requested service pack currently. SP2 provides: support for Bluetooth 2.1 / 3.0 (only beta driver is available for Bluetooth 3.0), support for 64-bit VIA processors, the ability to write optical discs in Blu-ray format (eng, "Blue ray" - got its name from the shortwave (405 nm) "blue" laser used for recording and reading, the letter "e" was deliberately excluded from the word blueto register the name as a trademark), easier wireless Wi-Fi setup (Windows Connect Now Wizard, WCN), 1CCD / CCID smart card support, better HD video playback performance, etc. In addition, it should be noted that SP2 cannot be installed without first installing SP1. This is done in order to combine SP for two platforms - Windows Vista and Windows Server 2008.

On May 25, 2009, SP2 for Windows Vista and Windows Server 2008 became available for public download from the Microsoft website in English, German, Spanish, French and Japanese, and on July 1, 2009, SP2 for Windows Vista in Russian became available. for automatic installation via Windows Update.

Let's list the main features provided to the user of Windows Vista OS in comparison with OS Windows XP Professional, which can be interpreted as distinctive features of this OS in comparison with OS Windows XP Professional:

  • Windows Vista boot time is faster than Windows XP, and the time to enter and wake up from sleep mode is reduced to 6 seconds. However, after loading the user interface, it takes a longer time to start full-fledged work, while background processes that greatly complicate the work of user programs pass;
  • ? thanks to the use of "Windows Ready Boost" technology, it became possible to use external flash memory as RAM, which in some cases increases OS performance by 40%;
  • application of a complex of technical solutions Windows Aero (Aero is an abbreviation from English, authentic - authentic, energetic -vigorous, reflective - responsive and open - open). Windows Aero uses window animations when opening, closing, minimizing, and restoring to make the operating system more intuitive. Transparent window elements with background blur allow the user to concentrate only on the content of the active window, etc .;
  • better protection against hacker attacks and computer viruses, especially network viruses;
  • the logical model of interaction between the OS and graphic devices has been completely redesigned.

Windows 7 OS belongs to the line of operating systems of the Microsoft Windows NT family, and in particular it is Windows NT 6.1, used mainly on personal computers.

Windows 7 officially went on sale on October 22, 2009, i.e. less than three years after the previous Windows Vista was released. Microsoft has introduced six editions of Windows 7: Windows 7 Starter (Initial OS), Windows 7 Home Basic (Home Basic), Windows 7 Home Premium (Home Extended), Windows 7 Professional (Professional) OS), Windows 7 Enterprise (Enterprise OS) and Windows 7 Ultimate (Maximum OS). All of the above editions, with the exception of Windows 7 Starter, exist in both 32-bit and 64-bit versions.

It is easy to see that the number of released editions of Windows Vista and Windows 7 is the same, in addition, some of the names of editions, their features and capabilities coincide, therefore we will not dwell here on the features and capabilities of each edition of Windows 7, but we will only note the main features, distinguishing Windows 7 from Windows Vista:

  • Windows 7 uses multitouch - a technology that allows you to simultaneously detect and determine the coordinates of at least three touch points on a multitouch screen;
  • "Branch Cache" network technology used in Windows 7 allows efficient caching of information coming from the Internet;
  • closer integration with driver manufacturers, most of them are automatically detected, while in 90% of cases backward compatibility with drivers for Windows Vista is preserved;
  • ? a new, 11th version of DirectX, released as part of Windows 7, has been applied, which has the following advantages over existing versions: added support for new computing shaders (massive parallel computing), multithreaded rendering (the process of obtaining an image from a model using a computer program), improved tessellation (in computer graphics, a way by which it is possible to increase the number of polygons in a polygonal three-dimensional model using Bezier curves), new texture compression algorithms have appeared, etc .;
  • Windows 7 supports folder aliases internally; for example, the Program Files folder in some localized versions of Windows was translated and displayed with the translated name, but at the file system level it remained in English;
  • Windows 7 is more compatible with Windows XP than Windows Vista (SP1, SP2); for example, it was not possible to run some old Windows XP programs on Windows Vista;
  • the security of Windows 7 has been improved, so the likelihood of computer viruses getting into Windows 7 is 25% lower than in Windows Vista and 20% less than in Windows Vista SP2. Windows 7, which entered the market, as well as previous operating systems,

maintained by Microsoft Corporation. The final Russian version of the first Service Pack 1 (SP1) for Windows 7 was released in the first quarter of 2011. SP1 mainly includes bug fixes and patches for vulnerabilities identified since the platform was announced in October 2009. The update contains everything patches - Automated, separately supplied software tools used to resolve identified issues in the underlying software product.

Computer science - operating system (OS) - The main tasks of the OS - User interface - Characteristics, shells

An operating system (OS) is a collection of software tools that manage the hardware resources of a computer, support the execution of programs, and interact programs with hardware, other programs, and the user.

The OS is the basic software, without which the computer cannot work. Therefore, any type of computer is equipped with an OS. Usually there are several types of OS, oriented to the same type of computer. The main part of the OS, the kernel, is loaded into RAM when the computer is turned on and is there constantly during the entire period of the computer's operation (i.e., resident).

Application programs can only run in an operating system environment. For each type of OS, its own set of application programs (applications) is developed.

The situation when a program developed for one operating system can be directly executed in the environment of another operating system is rare. More often, software products focused on a particular OS cannot function in the environment of another OS (software incompatibility).

The main purpose of the operating system is the connection between software products and directly the hardware of the computer. The operating system makes the programs to a certain extent independent of the specific modification of the machine and the equipment installed on it. It also allows the user to "tell" what they want from the computer.

The operating system has some conventions and restrictions in place in order for it to "understand" the user's wishes. Dialogue with the operating system is somewhat like a conversation with a stupid, dull, but executive servant. She understands you only when you tell her where what lies and what to do with it, and if you say this inaccurately, then she can do something completely different or refuse to do anything at all.

The main tasks of the OS

1.support the work of programs; ensuring their interaction with the hardware and with each other;

2. resource allocation (processor time, RAM, disk space, etc.); the organization of the file system (data storage systems on external media); resource usage accounting, video system management;

3. processing of error situations; protection of information;

4. support for the ability for the user to control the machine using special commands (processing the command language in a procedural environment) or acting on certain objects (buttons, etc. in an object-oriented environment);

5. network support.

User interface

In addition to managing resources and supporting the operation of programs, the OS provides the user with the ability to control the computer in dialogue mode. This is done using the user interface.
User interface is a component of a software product that provides dialog interaction between the program and the user.

The simplest form of UI is the command line interface. It assumes control of the computer by entering commands from the keyboard.

A prime example is the MS-DOS command line:

C: \\ USERS \\ DIPLOM \\\u003e copy head.htm C: \\ USERS \\ BAKALAVR

1 file copied

A more convenient type of UI is a text window interface. It does not require typing commands on the keyboard, but reduces control to pressing individual keys or mouse buttons when selecting control actions in menus and dialog boxes.

An example is the Borland Pascal shell:

The most modern is the graphical window interface, which combines the developed dialogue tools of the window interface (menu systems, dialog boxes, toolbars, icons, etc.) with the large visual capabilities of the graphical mode.

An example is the My Computer folder window:

----

OS characteristics

1.bit (for PC 8-bit, 16-bit, 32-bit, 64-bit OS);

2. the number of programs simultaneously executed under the control of the OS (single and multitasking OS).
Multitasking operating systems support the parallel execution of several programs running on one computer system at the same time. Multitasking can be corporate and preemptive.
With corporate multitasking, applications share a processor by periodically transferring it to each other. If some application refuses to free the processor, the system cannot do anything about it.
If preemptive multitasking is used, the operating system completely controls all applications and distributes processor time between them, thereby greatly reducing the likelihood of the system "hanging" in the event of errors in the operation of programs.
Single-tasking operating systems support the mode of execution of only one program at a time;

3. multithreading is a technology that allows an application to properly multitask its processes. Process is any task or activity initiated by a program. One program can execute several processes at the same time;

4. type of user interface: command line interface, text window interface, graphical window user interface (ICS, TYPE, GUI);

5. the requirement for hardware resources;

6. performance;

7. reliability (stability in operation, data protection from unauthorized access);

8. security of applied programs;

9. availability of network capabilities (network, local OS);
Network operating systems are designed to manage the resources of computers connected to a network for the purpose of sharing data, and provide powerful means of differentiating access to data while ensuring their integrity and safety, as well as many service capabilities for using network resources;

10. number of supported processors: uniprocessor, multiprocessor;
Multiprocessor operating systems, in contrast to uniprocessor ones, support the use of multiple processors to solve one problem;

11. the openness of the operating system, is that the components of the OS are available in source codes for any user.

12. way of using RAM;
There are two ways to work with memory: linear address - the OS works with the entire system memory as a single continuous space; segmental - the OS works with a small amount of RAM available without special means.

The most common computer operating systems

The main characteristics of operating systems are:

The first representative of this family is the system MS-DOS (Microsoft Disk Operating System) was released in 1981 in connection with the advent of the IBM PC.
Operating systems of the DOS family are single-tasking 16-bit ones and have the following features:

Command line interface
Modularity of the structure, simplifying the transfer of the system to other types of computers
A small amount of RAM available without special means (640 KB)
Low hardware requirements, large amount of application programs.

A significant drawback of operating systems of the DOS family is the lack of protection against unauthorized access to PC and OS resources, as well as low reliability, lack of network capabilities. Currently MS DOS is part of Windows 95 OC.

GETTING STARTED ABOUT MS-DOS

The MS-DOS operating system itself (and any other operating system too) consists of several parts:

An operating system loader is a small program stored in the first sector of any system floppy disk (a floppy disk with an operating system on it) or hard drive that loads two system files io.sys and msdos.sys into memory. It is the operating system loader that transfers control to the BIOS at the initial start of the machine.

The files io.sys and msdos.sys are permanently located in the computer's memory during operation: io.sys complements the basic I / O system depending on the needs of this version of the operating system, and msdos.sys implements all the standard functions of this version. In addition, msdos.sys loads the command processor into memory.

The command processor (command.com file) maintains the system's interaction with the user. It itself executes some of the operating system commands (these commands are called internal), and when calling external commands or executing other programs, it transfers control to them, at the end of their work, it again takes control and unloads the program that has been run from memory.
External commands of the operating system are separate programs that perform any service functions.

Device drivers are special resident programs, their main purpose is to expand the capabilities of individual computer devices (for example, memory), connect additional equipment (say, a mouse) and ensure the normal operation of non-standard devices.

Let us now consider the principles of organizing information storage in a computer.

Operating system skins

An OS shell is an add-on over the operating system that greatly facilitates the user's work and provides him with a number of additional services.

Operating system skins provide:

* create, rename, copy, transfer, delete and quickly search for a file in the current disk directory or on all disks of the computer;
* viewing, creating and comparing catalogs;
* viewing, creating and editing text files;
* archiving, updating and unzipping archive files and viewing archives;
* directory synchronization, splitting and merging files;
* Support for communication between two computers via serial or parallel ports;
* formatting and copying floppy disks, changing the floppy disk label and volume label for hard drives, as well as cleaning disks from unnecessary files;
* launching programs.

The most popular among users was the Norton Commander (NC) shell. This software product allows you to see files and directories on two constantly displayed panels of several types and conveniently manipulate files using the function keys and the mouse.

The DOS Navigator shell completely copies the original NC idea, but has additional functions. It supports work with a large number of archivers, allows you to highlight files of various types in color, has more convenient means for intercomputer communication via a modem.

Graphical shells for Windows - Dash Board for Windows, Dash Board for Windows 95, DeskBar 95 for Windows 95 - allow the user to quickly create menus for launching programs and calling documents, as well as control the use of system resources.

Shez and RAR shells are designed to manage compression (archiving) and unpacking files in MS-DOS environment. The WinRAR and WinZir shells are designed to control compression (archiving) and unpacking files in a graphical environment. NDOS shells, Norton Desktop for Windows are designed to manage files.

Date of publication: 01.10.2010 10:34 UTC

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To determine the operational characteristics, first of all, a decision matrix is \u200b\u200bcompiled, which is based on a study of a cohort of patients, consisting of two groups - healthy and patients with a precisely verified (reference) diagnosis of the disease (tab.

Table 9.1.

Decision matrix for calculating the operational characteristics of diagnostic methods

The operational characteristics of the diagnostic method include:

1.sensitivity (Se, sensitivity),

2.specificity (Sp, specificity),

3.accuracy (Ac, accuracy), or the effectiveness of the diagnosis

4.the predictive value of a positive result (+ VP, positive predictive value),

5. the predictive value of a negative result (-VP, negative predictive value).

Some of the above criteria for the information content of radiation diagnostics are variable. They depend on the prevalence of the disease, or prevalence.

Prevalence (Ps) is the probability of a particular disease, or more simply, its frequency of occurrence among the studied group of people (cohort) or the population as a whole. An incident (In) should be distinguished from prevalence - the probability of a new disease in the considered group of people over a certain period of time, more often in one year.

Sensitivity (Se) is the proportion of correct positive test results among all patients. Determined by the formula:

where Se - sensitivity, TP - true positive cases, D + - the number of patients with the disease.

Sensitivity a priori shows what will be the proportion of patients in whom this study will give a positive result. The higher the sensitivity of the test, the more often the disease will be detected with its help, the more effective it is, therefore. At the same time, if such a highly sensitive test is negative, then the presence of the disease is unlikely. Therefore, they should be used to rule out disease. Because of this, highly sensitive tests are often referred to as identifiers.

xia to narrow the range of alleged diseases. It should also be noted that a highly sensitive test gives a lot of "false alarms", which requires additional financial costs for further examination.

Specificity (Sp) is the proportion of correct negative test results among healthy patients. This indicator is determined by the formula

where Sp - specificity, TN - true negative cases, D- - healthy patients.

Having determined the specificity, one can a priori assume what the proportion of healthy individuals in whom this study will give a negative result. The higher the specificity of the method, the more reliably the disease is confirmed with its help, the more effective it is, therefore. Highly specific tests are called discriminators in diagnostics. Highly specific methods are effective at the second stage of diagnosis, when the range of suspected diseases is narrowed and it is necessary to prove the presence of the disease with great confidence. The negative factor of the highly specific test is the fact that its use is accompanied by a very significant number of missed diseases.

A very important practical conclusion follows from the above, which is that in medical diagnostics, a test is desirable that would be a priori both highly specific and highly sensitive. However, in reality this cannot be achieved, since an increase in the sensitivity of the test will inevitably be accompanied by a loss of its specificity and, conversely, an increase in the specificity of the test is associated with a decrease in its sensitivity. Hence, the conclusion follows: in order to create an optimal diagnostic system, it is necessary to find a compromise between the indicators of sensitivity and specificity, in which the financial costs of the examination will optimally reflect the balance between the risks of "false alarms" and missed diseases.

Accuracy (Ac), or informativeness of the diagnostic test. is the proportion of correct test results among all examined patients. It is determined by the formula:

where Ac - accuracy, TP - truly positive decisions, TN - truly negative decisions, D + - all healthy patients, D- - all sick patients.

Accuracy, therefore, reflects how many correct answers were obtained as a result of testing a given test.

For a correct understanding of the diagnostic effectiveness of methods, an important role is played by the criteria of a posteriori probability - the predictive value of positive and negative results. It is these criteria that show what the probability of the disease (or its absence) is with a known research result. It is easy to see that the posterior indicators are more important than the prior ones.

The positive predictive value (+ VP) is the proportion of correct positive cases among all positive test scores. This indicator is determined by the formula

where + PV - positive predictive value, TP - true positive cases, FN - false negative cases.

The predictability of a positive result, therefore, directly shows how likely the disease is with positive results of a diagnostic study.

The negative predictive value (-VP) is the proportion of true negative cases among all negative decisions. The criterion is determined by the formula

where -PV - negative predictive value, TN - true negative cases, FP - false positive cases.

This indicator, therefore, shows how likely it is that the patient is healthy if the results of the radiation examination are negative.

Let us explain the methodology for calculating the operational characteristics of a diagnostic test using the following example.

Suppose a new digital fluorography method is being developed. It is necessary to assess its informative value in the diagnosis of lung diseases. For this purpose, patients are selected with an impeccably and accurately established diagnosis of this disease. Suppose a total of 100 patients of each group are selected, i.e. compiled two cohorts of observations. In the first group of tuberculosis patients, the fluorographic test was positive in 88 patients, and in 12 people it was negative. Of the second group of patients, 94 people were recognized as healthy, 6 patients were suspected of tuberculosis, and they were sent for further examination. Based on the data obtained, a decision matrix is \u200b\u200bcompiled (Table 9.2).

Table 9.2

Distribution of patients by disease and test results

The results of calculations according to the data presented in the table allows you to determine the diagnostic information content, i.e., to determine the sensitivity (Se), specificity (Sp), accuracy (Ac), the probability of positive (+ VP) and negative responses (-VP):

Thus, the operational characteristics of this method will be as follows: sensitivity - 88%, specificity - 96%, accuracy - 92%, predictive value of a positive result - 96%, predictive value of a negative result - 89%.

If such operational characteristics of tests as sensitivity, specificity and accuracy do not significantly depend on the incidence of the disease, then the predictive value of the results, both positive and negative, is directly related to the prevalence. The higher the prevalence of the disease, the higher the predictive value of a positive result and the lower the predictive value of a negative test. Indeed, it is a well-known fact that overdiagnosis of a doctor working in a specialized hospital is always higher than that of the same doctor working in a general polyclinic. Naturally, it is understood that the qualifications of both specialists are equivalent.

There is a mutual influence of the characteristics of radiation tests. So, the higher the sensitivity of the radiation method, the higher the predictive value of its negative result. The predictability of a positive radiation test result mainly depends on its specificity. Low-specific methods are accompanied by the emergence of a large number of false positive decisions. This leads to a decrease in the predictive value of positive results of radiation studies.

The above criteria for the informativeness of diagnostics are based on the principles of dichotomous decisions: "yes" - "no", "norm" - "pathology". However, it is well known that in the practical work of a doctor it is not always possible to classify the data obtained according to a similar scheme. In some cases, a specialist may also have other conclusions, such as, for example, "most likely there is a disease" or "most likely, there is no disease." Such nuances in the acceptance of medical opinions reflect other characteristics of information content - likelihood ratio.

The likelihood ratio of a positive result (+ Lr) shows how many times the probability of obtaining a positive result is higher in patients than in healthy people. The appropriate

thus, the likelihood ratio of a negative result (-Lr) shows how many times the likelihood of obtaining a negative result in healthy patients is higher than in patients. These criteria for the informativeness of diagnostics are determined based on the table above, according to the following formulas:

In medical practice, it is often necessary to use several diagnostic methods. The use of several beam studies can be performed in two ways: in parallel and in series.

The parallel use of tests is often used in the diagnosis of emergency conditions of the patient, i.e. in cases where it is necessary to carry out the maximum amount of diagnostic procedures in a short time. The parallel application of tests provides their greater sensitivity and, consequently, a higher predictive value of a negative result. At the same time, the specificity and predictive value of a positive result decreases.

The sequential application of tests is performed when clarifying the diagnosis, to detail the patient's condition and the nature of the pathological process. With the consistent use of diagnostic tests, the sensitivity and predictive value of negative test results decreases, but at the same time, the specificity and predictive value of a positive result increase.

Thus, a combination of various research methods and a change in the order of their execution change the set of operational characteristics of each test separately and the general predictability of their results. From the above, an important conclusion of evidence-based medicine follows: the prognostic characteristics of any test cannot be automatically transferred to all medical institutions without taking into account the prevalence and a number of other circumstances.

When assessing the diagnostic effectiveness of a research method, they usually indicate the total number of erroneous conclusions: the fewer, the more effective the method. However, as already noted, it is unrealistic to simultaneously reduce the number of false positive and false negative errors, since they are related. In addition, it is generally accepted that errors of the first type - false positives - are not as dangerous as errors of the second type - false negatives. This especially applies to the detection of infectious and oncological diseases: it is many times more dangerous to miss a disease than to diagnose it in a healthy person.

In cases where the results of a diagnostic study are expressed quantitatively, they are classified into norm and pathology conditionally. Some of the test values \u200b\u200btaken as the norm will be observed in patients, and, conversely, some changes in healthy people will appear in the pathology zone. This is understandable: after all, the border between health and the initial stage of the disease is always conditional. And yet in practical work, analyzing the digital indicators of a diagnostic study, the doctor is forced to make alternative decisions: to classify this patient as a healthy or sick group. In doing so, he uses the dividing value of the test used.

A change in the border between norm and pathology is always accompanied by a change in the operational characteristics of the method. If more stringent requirements are imposed on the method, i.e. the border between norm and pathology is established at high test values, the number of false negative conclusions (missed diseases) increases, which leads to an increase in the specificity of the test, but at the same time to a decrease in its sensitivity. If it is advisable to soften the requirements for the test, the border between norm and pathology is shifted towards normal values, which is accompanied by an increase in the number of false-positive conclusions (false alarms) and, at the same time, a decrease in the number of false-negative (missing diseases). This increases the sensitivity of the method, but decreases its specificity.

Thus, conducting diagnostic studies and evaluating their results quantitatively, the doctor is always in the conditions of choice: either he sacrifices sensitivity in order to increase specificity, or, on the contrary, prefers specificity due to a decrease in sensitivity. How to do the right thing in each case depends on many factors: the social significance of the disease, its nature, the patient's condition, and, no less important, on the psychological characteristics of the doctor's personality.

From the above, the most important conclusion for modern medical diagnostics follows. The quantitative mathematical method, no matter how perfect the mathematical apparatus or technical means, its results always have a limited, applied value, obeying the logical thinking of the doctor and correlating with a specific clinical and social situation.

The theory of evidence-based medicine has shown that the differentiation of groups of patients by health status into norm and pathology is conditional and depends on the point of separation of these states depending on the subjective qualities of the researcher - his decisiveness or caution, as well as on other prerequisites - external and internal. In fig. 9.2 presents a coordinate system that reflects decision-making in medicine. The ordinate is an indicator of morbidity, and the abscissa is the diagnostic decision making, i.e. ... It is noteworthy that the curves of the Poisson distribution, reflecting the totality of norm and pathology, are mutually superimposed on each other. This forms a graphical distribution of correct and erroneous decisions in diagnostics - both positive and negative: exact hits, omissions, false alarms.

Figure 9.2. The relationship between test results and decision criteria. PI - truly positive results,

IO - true negative, LP - false positive, LO - false negative

The X point on the decision axis is the dividing point of the results into positive and negative. To the left of this axis are correctly negative decisions and omissions of the disease, to the right of the axis are correctly positive decisions and false alarms. The relationship of these indicators forms a graphical representation of the operational characteristics of the research method. This picture is superimposed on the characterological characteristics of the doctor's personality. If the doctor is cautious, the decision-making axis shifts to the left, if decisive - to the right. The relationship between the operational characteristics of the diagnostic test used is changing accordingly. The d interval denotes the value of the disease recognition criterion.

The structure and capabilities of operating systems evolve year after year. Recently, new operating systems and new versions of existing operating systems have included some structural elements that have made great changes in the nature of these systems. Modern operating systems meet the demands of constantly evolving hardware and software. They are able to control the operation of multiprocessor systems that run faster than conventional machines, high-speed network devices and a variety of storage devices, the number of which is constantly increasing. Among the applications that have influenced the design of operating systems are multimedia applications, Internet access, and the client / server model.

The relentless increase in requirements for operating systems leads not only to better architecture, but also to the emergence of new ways of organizing them. A wide variety of approaches and building blocks have been tried in experimental and commercial operating systems, most of which can be grouped into the following categories.

  • - Microkernel architecture.
  • - Multithreading.
  • - Symmetric multiprocessing.
  • - Distributed operating systems.
  • - Object oriented design.

A distinctive feature of most operating systems today is a large monolithic kernel. The kernel of the operating system provides most of its capabilities, including scheduling, working with the file system, networking, device drivers, memory management, and many others. Typically, a monolithic kernel is implemented as a single process, all of whose elements use the same address space. In microkernel architecture, the kernel has only a few of the most important functions, including address spaces, interprocess communication (IPC), and basic scheduling. Other operating system services are run by processes that are sometimes called servers. These processes are launched in user mode and the microkernel works with them in the same way as with other applications.

This approach separates the task of operating system development into kernel development and server development. Servers can be configured to meet the requirements of specific applications or environments.

Allocating a microkernel in the system structure simplifies the implementation of the system, ensures its flexibility, and also fits well into a distributed environment.

Multithreading is a technology in which a process running an application is split into several concurrently executing threads. Following are the main differences between thread and process.

Flow:A dispatched unit of work that includes the processor context (which includes the contents of the program counter and the top of the stack pointer) and its own stack area (for organizing subroutine calls and storing local data). Stream commands are executed sequentially; a thread can be interrupted when the processor switches to processing another thread.

Process: A collection of one or more threads, as well as the system resources associated with those threads (such as an area of \u200b\u200bmemory containing code and data, open files, various devices). This concept is very close to the concept of a running program. By splitting the application into multiple threads, the programmer takes full advantage of the application's modularity and the ability to manage application-related timing events.

Multithreading turns out to be very useful for applications that perform multiple independent tasks that do not require sequential execution. An example of such an application is a database server that simultaneously accepts and processes multiple client requests. If multiple threads are being processed within the same process, then switching between different threads has less CPU overhead than switching between different processes. In addition, threads are useful in structuring processes that are part of the operating system kernel, described in later chapters.

Until recently, all single user personal computers and workstations contained a single general purpose virtual microprocessor. As a result of the ever-increasing demands for performance and lowering the cost of microprocessors, manufacturers have moved towards multi-processor computers.

To improve efficiency and reliability, symmetric multiprocessing (SMP) technology is used.

This term refers to the hardware architecture of a computer, as well as the operating system's behavior that matches that architectural feature. Symmetric multiprocessing can be defined as a stand-alone computer system with the following characteristics.

  • - The system has multiple processors.
  • - These processors, interconnected by a communication bus or some other circuitry, share the same main memory and the same I / O devices.
  • - All processors can perform the same functions (hence the name symmetric processing).

An operating system running on a symmetric multiprocessor system distributes processes or threads across all processors. Multiprocessor systems have several potential advantages over uniprocessor systems, including the following.

Performance. If a job to be performed by a computer can be structured so that parts of the job are executed in parallel, this will result in improved performance over a uniprocessor system with the same type of processor. The above statement is illustrated in Fig. 2.12. In multitasking mode, only one process can run at the same time, while the rest of the processes are forced to wait for their turn. In a multiprocessor system, multiple processes can run concurrently, each running on a separate processor.

Reliability. In symmetric multiprocessing, a failure of one of the processors will not bring the machine to a standstill, because all processors can perform the same functions. After such a failure, the system will continue to work, although its performance will decrease slightly.

Building up. By adding additional processors to the system, the user can improve its performance.

Scalability. Manufacturers can offer their products in various configurations that vary in price and performance, designed to work with different numbers of processors.

It is important to note that the benefits listed above are potential rather than guaranteed. To properly realize the potential inherent in multiprocessor computing, the operating system must provide an adequate set of tools and capabilities.

Figure 4 Multitasking and multiprocessing

You can often find a joint discussion of multithreading and multiprocessing, but the two concepts are independent. Multithreading is a useful concept for structuring application and kernel processes, even on a single processor machine. On the other hand, a multiprocessor system can have advantages over a uniprocessor system, even if the processes are not split into multiple threads, because such a system can run multiple processes at the same time. However, both of these possibilities are in good agreement with each other, and their combined use can give a noticeable effect.

A tempting feature of multiprocessor systems is that the presence of multiple processors is transparent to the user - the operating system is responsible for distributing threads between processors and synchronizing different processes. This book discusses the scheduling and synchronization mechanisms that are used to ensure that all processes and processors are visible to the user as a single system. Another higher-level task is to represent a cluster of several separate computers as a single system. In this case, we are dealing with a set of computers, each of which has its own main and secondary memory and its own I / O modules. A distributed operating system creates the appearance of a single space of primary and secondary memory, as well as a single file system. Although the popularity of clusters is steadily increasing and more cluster products are appearing on the market, modern distributed operating systems still lag behind in the development of single and multiprocessor systems. You will get acquainted with such systems in the sixth part of the book.

One of the latest innovations in the design of operating systems is the use of object-oriented technologies. Object-oriented design helps to clean up the process of adding additional modules to the main small core. At the operating system level, an object-oriented structure allows programmers to customize the operating system without compromising its integrity. In addition, this approach facilitates the development of distributed tools and complete distributed operating systems.

Today, a huge part of the world's population constantly interacts with computers, someone is obliged to work, someone is looking for information on the Web, and someone just spends time in games. Everyone has their own needs, which means that the computer must meet them. And if we are talking about "hardware" (the technical component of a computer), then everything is more or less clear: the newer the better. But the “software” (software) part requires special attention.

Each computer runs a specific operating system, of which there are a great many, each of which is suitable for certain tasks, available equipment, and so on. Therefore, the choice of this operating system is an important factor.

There is a fairly massive list of operating systems, but this article will focus on three pillars that have strongly influenced the industry and occupy the bulk of all operating systems: Windows, MacOS, and Linux.

Proprietary operating systems

To begin with, it is worth clarifying that there are proprietary operating systems, those that are distributed under the manufacturer's license. These include Windows, which are listed below, and MacOS. Although both systems can be downloaded from the Web (stolen), it is correct to purchase a license from a distribution company and activate it.

The advantage of such systems is their development, a huge amount of high-quality software and competent technical support that will help in case of problems.

"Free" operating systems

This includes almost the entire Linux family, with the exception of some developments with accounting or other professional software. These OS can be downloaded absolutely free and installed on any computer without a twinge of conscience.

Such systems are created by independent developers together with the community, therefore, in most cases, the quality of programs leaves much to be desired, but such systems are much more secure and work more stable than their proprietary competitors.

Windows

Absolutely everyone who has ever dealt with a computer knows about this Microsoft product. In particular, this concerns the super-successful release of Windows 7. The list of Microsoft operating systems is already a dozen generations old. They are extremely popular all over the world and occupy almost 90% of the market. Which speaks of unprecedented leadership.

  • Windows XP;
  • Windows Vista;
  • Windows 7;
  • Windows 8;
  • Windows 10;

The list deliberately starts with Windows XP, as it is the oldest version still in use today.

Chrome OS

An underdeveloped product from Google, which is limited only to web applications and the browser of the same name. This system is not competitive with Windows and Mac, but it is made with an eye to the future, when web interfaces can replace "real" software. Installed by default on all Chromebooks.

Installing multiple systems and using virtual machines

Since each platform has its own pros and cons, it is often necessary to work with several at once. Computer designers are aware of this, so they offer users the ability to install two or three systems on a disk at once.

This is done simply. All you need is the system distribution kit (disk or flash drive with the installation material loaded on them) and free space on the hard disk. All modern operating systems offer to allocate space during installation and create a boot mechanism that will show a list of operating systems when the computer boots. Everything is done in a semi-automatic mode and can be done by any user.

Apple computers have a special utility - BootCamp, which is designed to easily and seamlessly install Windows alongside macOS.

There is another way - installing a virtual system inside a real one. For this, programs are used: VmWare and VirtualBox, capable of emulating the work of a full-fledged computer and running operating systems.

Instead of a conclusion

The list of operating systems for the computer is not limited to the above. There are many products from different companies, but all of them are quite specific and do not deserve the attention of an ordinary user. The choice should be made between Windows, macOS and Linux, as they can cover most of the needs and are quite easy to learn.

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