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The operating system is its general characteristic. List of operating systems: features, characteristics and reviews

Year after year, the evolution of the structure and capabilities of operating systems. Recently, some of the existing operating systems and new versions of existing operating systems have entered some structural elements that made large changes in the nature of these systems. Modern operating systems meet the requirements of constantly developing hardware and software. They are able to manage the work of multiprocessor systems operating faster than ordinary machines, high-speed network devices and a variety of storage devices, the number of which is constantly increasing. From applications that have an impact on the operating system device, you should mark multimedia applications, Internet access tools, as well as a client / server model.

The steady increase in the requirements for operating systems leads not only to improving their architecture, but also to the emergence of new methods of their organization. In experimental and commercial operating systems, a wide variety of approaches and structural elements were tested, most of which can be combined into the following categories.

  • - microker architecture.
  • - multithreading.
  • - symmetric multiprocessing.
  • - Distributed operating systems.
  • - object-oriented design.

A distinctive feature of most operating systems today is a large monolithic core. The kernel of the operating system provides most of its capabilities, including planning, work with the file system, network functions, operation of drivers of various devices, memory management and many others. Typically, the monolithic kernel is implemented as a single process, all the elements of which use the same address space. Only the most important functions are allocated to the kernel microker architecture, including work with targeted spaces, interaction between processes (InterProcessCommunication - IPC) and basic planning. The operation of other operating system services provide processes that are sometimes called servers. These processes are started in user mode and microkerbo works with them as well as with other applications.

This approach allows us to divide the task of developing an operating system to develop the kernel and server development. Servers can be configured for specific applications or environments.

The selection of the microker system in the structure simplifies the implementation of the system, ensures its flexibility, and also fits well into the distributed medium.

Multipleness (MULTITHREADING) is a technology in which the process running the application is divided into several simultaneously performed flows. Below are the main differences between the stream and the process.

Flow:The dispatching unit of work, including the processor context (which includes the contents of the software counter and the stack vertex), as well as its own stack area (to organize the call of subroutines and storing local data). Flow commands are performed sequentially; The stream can be interrupted when switching the processor to the processing of another stream.

Process: A set of one or several streams, as well as related system resources related streams (such as the memory area, which includes code and data, open files, Various devices). This concept is very close to the concept of the executing program. By breaking the application into several streams, the programmer receives all the advantages of the application modularity and the ability to control the application-related applications.

Multipleness turns out to be very useful for applications that perform several independent tasks that do not require sequential execution. As an example of such an application, you can bring the database server that simultaneously receives and processes several customer requests. If several streams are processed within the same process, then when switching between different threads, non-production consumption of processor resources is less than when switching between different processes. In addition, the streams are useful when structuring processes described in subsequent chapters, which are part of the operating system core.

Until recently, all personal computers designed for one user and workstations contained one general-purpose virtual microprocessor. As a result of a constant increase in the performance requirements and lowering the cost of microprocessors, manufacturers moved to the release of computers with multiple processors.

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

This term refers to the computer hardware architecture, as well as to the image of the operating system, corresponding to this architectural feature. Symmetrical multiprocessing can be defined as an autonomous computer system with the following characteristics.

  • - There are several processors in the system.
  • - These processors, interconnected by a communication bus or some other scheme, share the same basic memory and the same input-output devices.
  • - All processors can perform the same functions (hence the name symmetric processing).

The operating system operating in a system with symmetric multiprocessing distributes processes or streams between all processors. In multiprocessor systems there are several potential advantages compared to single-processor, including the following.

Performance. If the task that the computer must be executed can be organized so that some parts of this task will be performed in parallel, this will lead to an increase in productivity compared to a single-processor system with the processor of the same type. The above position is illustrated in fig. 2.12. In multitasking mode, only one process can be performed in the same time, while the remaining processes are forced to expect their turn. In a multiprocessor system, several processes can be performed simultaneously, each of them will work on a separate processor.

Reliability. With a symmetric multiprocessor processing, one of the processors fails to stop the machine, because all processors can perform the same functions. After such a failure, the system will continue its work, although its performance will decrease somewhat.

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

Scalability. Manufacturers can offer their products in various, differing costs and performance, configurations designed to work with different number of processors.

It is important to note that the advantages listed above are rather potential than guaranteed. In order to properly implement the potential enclosed in multiprocessor computing systems, the operating system should provide an adequate set of tools and capabilities.

Figure 4 Multitasking and multiprocessing

Often you can meet a joint discussion of multithreading and multiprocessing, but these two concepts are independent. Multipleness is a useful concept for structuring application and kernel processes even by car with one processor. On the other hand, a multiprocessor system may have advantages compared to single-processor, even if processes are not divided into several threads, because in such a system, several processes can be started at the same time. However, both of these possibilities agree well with each other, and their sharing can give a noticeable effect.

The tempting feature of multiprocessor systems is that the presence of multiple processors is transparent to the user - for the distribution of flows between processors and the synchronization of different processes is responsible for the operating system. This book discusses planning and synchronization mechanisms that are used so that all processes and processors are visible to the user in the form of unified system. Another higher level task is a representation in the form of a single cluster system from several separate computers. In this case, we are dealing with a set of computers, each of which has its own main and secondary memory and its input-output modules. The distributed operating system creates the visibility of a single space of primary and secondary memory, as well as a single file system. Although the popularity of clusters steadily increases and increasingly cluster products appear on the market, modern distributed operating systems are still lagging behind in the development of withdrawal and multiprocessor systems. With such systems you will get acquainted in the sixth of the book.

One of the latest innovations in the operating system device was the use of object-oriented technologies. Object-oriented design helps to bring order in the process of adding to the main small kernel. additional modules. At the operating system level, an object-oriented structure allows programmers to customize the operating system without disturbing its integrity. In addition, this approach facilitates the development of distributed tools and full-fledged distributed operating systems.

To determine the operational characteristics, first of all make up the solutions matrix, which is based on the study of cogators of patients consisting of two groups - healthy and patients with precisely verified (reference) diagnosis of the disease (Table.

Table 9.1.

Matrix solutions for calculating operational characteristics of diagnostic methods

The operational characteristics of the diagnostic method include:

1. Sensitivity (SE, SENSITITIVITY),

2. Specificity (SP, SPECIFICITY),

3. Accuracy (AC, Accuracy), or diagnostic efficiency

4. Prognostability of the positive result (+ VP, POSITIVE PREDICTIVE VALUE),

5. Prognostability of the negative result (-VP, Negative Predictive Value).

Some of the above criteria for the informativeness of radiation diagnostics are inconsistent. They depend on the prevalence of the disease, or prehanta.

Prevalance (PS) is the likelihood of a certain disease, or simpler, its frequency of occurrence among the studied group of people (cohorts) or population as a whole. From Prealance should be distinguished by an incident (IN) - the likelihood of a new disease in the group of people under consideration for a certain period of time, more often in one year.

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

where SE is sensitive, TP is true positive cases, D + is the number of patients with the presence of a disease.

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

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 the correct negative test results among healthy patients. This indicator is determined by the formula

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

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

From what was said, a very important practical conclusion, which is that in medical diagnosis, a test, which would be a priori as highly specific and highly sensitive was desirable. However, in reality it cannot be achieved, since the increase in test sensitivity will inevitably be accompanied by the loss of its specificity and, on the contrary, improving the specificity of the test is associated with a decrease in its sensitivity. It follows the conclusion: To create an optimal diagnostic system, it is necessary to find a compromise between sensitivity and specificity indicators, in which the financial costs for the survey will optimally reflect the balance between the risks of "false alarms" and skipping diseases.

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

where AC is accuracy, TP is true positive solutions, TN is true negative solutions, D + are all healthy patients, D- - all patients.

Accuracy thus reflects how much the right answers received as a result of testing of this test.

For the correct understanding of the diagnostic efficiency of the methods, the criteria of a posteriori probability are played by an important role - prognostility of positive and negative results. It is these criteria that show the likelihood of a disease (or its absence) with a known result of the study. It is easy to see that the recreation indicators are more important than a priori.

Prognostability of a positive result (+ VP) is a proportion of properly positive cases among all positive test values. This indicator is determined by the formula

where + PV is the prognostility of the positive result, TP is true positive cases, Fn is false negative.

The prognostility of the positive result is thus directly indicated how large the likelihood of the disease is the positive results of the diagnostic study.

The prognostility of the negative result (-vp) is the proportion of the right negative cases among all negative solutions. The criterion is determined by the formula

where -pv is the prognostility of the negative result, TN is true negative cases, FP - false positive cases.

This indicator thus shows how large the likelihood is that the patient is healthy, if the results of radiation research are negative.

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

Suppose a new method of digital fluorography is being developed. It is necessary to evaluate its informativeness in the diagnosis of lung diseases. For this purpose, patients with flawless and precisely established diagnosis of this disease are selected. Suppose everything is selected in 100 patients of each group, i.e. Two observation cohorts are compiled. In the first group of patients with tuberculosis, the fluorographic test turned out to be positive in 88 patients, and 12 people he was negative. From the second group of patients, 94 people were recognized as healthy, 6 patients had a suspicion of tuberculosis, and they were sent for further examination. Based on the obtained data, the matrix of solutions is compiled (Table 9.2).

Table 9.2.

Distribution of patients in the presence of disease and test results

The results of calculations according to the data set out in the table allows you to determine diagnostic informativeness, that is, to determine the sensitivity (SE), specificity (SP), accuracy (AC), the probability of positive (+ VP) and negative answers (-vp):

Thus, the operational characteristics of this method will look as follows: Sensitivity - 88%, specificity - 96%, accuracy - 92%, the prognostility of the positive result is 96%, the prognosticity of the negative result is 89%.

If such operational characteristics of tests, both sensitivity, specificity and accuracy do not significantly depend on the frequency of the disease, then the prognostility of the results, both positive and negative, is directly related to the prevaste. The higher the disease presented, the higher the prosecution of the positive result and below the prognostility of the negative test. Indeed, well known is the fact that hyperdiagnostics from a doctor working in a specialized hospital is always higher than that of the same doctor working in a common profile clinic. Naturally, it is understood that the qualifications of both specialists are equivalent.

There is a mutual influence of the characteristics of radial tests. So, the higher the sensitivity of the radiation method, the higher the prognostic value of its negative result. The accuracy of the positive result of the radiation research mainly depends on its specificity. Low-specific methods are accompanied by a large number of false positive solutions. This leads to a decrease in the prognosticity of the positive results of the radiation study.

The criteria for the informativeness of diagnostics listed above are based on the principles of dichotomous solutions: "Yes" - "no", "norm" - "pathology". However, it is well known that practical work The doctor does not always be able to classify the data obtained by such a scheme. In some cases, a specialist has other conclusions, such as, for example, "most likely, there is no disease" or "Most likely, there is no disease." Similar nuances in the adoption of medical conclusions reflect other characteristics of informativeness - likelihood relationship (Likelihood Ratio).

The attitude of the likelihood of a positive result (+ LR) shows how many times the likelihood of obtaining a positive result is higher in patients than in healthy. Corresponding

the way the attitude of the likelihood of a negative result (-lr) shows how many times the likelihood of obtaining a negative result in healthy patients is higher compared to patients. These criteria for informative diagnostics are determined based on the table presented above, according to the following formulas:

In medical practice, several diagnostic methods have to be applied very often. The use of several radial research can be performed in two options: in parallel and sequentially.

Parallel use of tests is often used in the diagnosis of urgent states of the patient, i.e. In cases where in a short time it is necessary to carry out the maximum coverage of the amount of diagnostic procedures. Parallel use of tests ensures their greater sensitivity, and, therefore, the higher prognostic value of the negative result. At the same time, the specificity and prognostic value of a positive result is reduced.

Sequential use of tests are performed when the diagnosis is specified, to detail the state of the patient and the nature of the pathological process. With a consistent application of diagnostic tests, the sensitivity and prognostic value of the negative results of the study are reduced, but at the same time the specificity and prognostic value of a positive result increase.

Thus, a combination of various research techniques, a change in the procedure for their execution changes a set of operational characteristics of each test separately and the overall productity of their results. From the above, an important conclusion of evidence-based medicine is followed: the prognostic characteristics of any test can not be automatically automatically, without registering the prevention and a number of other circumstances, to transfer to all therapeutic institutions.

Giving an assessment of the diagnostic efficiency of the research method, usually indicate the total number of erroneous conclusions: than them are less, the more effective method. However, as already noted, simultaneously reduce the number of false positive and falsely negative errors is unrealistic because they are interconnected. In addition, it is believed that the errors of the first type are falsely positive - not as dangerous as the errors of the second type are falsely negative. This is especially true for the identification of infectious and oncological diseases: to skip the disease is more dangerous than diagnosing it in a healthy person.

In cases where the results of the diagnostic study are quantified, they are classified to the norm and pathology conditionally. A part of the test values \u200b\u200btaken as the norm will be observed in patients, and, on the contrary, some changes in the disease will be in the zone of pathology. This is understandable: because the border between health and the initial stage of the disease is always conditional. And yet, in practical work, analyzing digital indicators of diagnostic research, the doctor is forced to accept alternative solutions: to include a given patient for a group of healthy or patients. At the same time, it uses the separation value of the applied test.

The change in the boundary between the norm and pathology is always accompanied by a change in the operational characteristics of the method. If more stringent requirements are presented to the method, i.e. The boundary between the norm and pathology is set at high test values, the number of false-negative conclusions (diseases of diseases) increases, which leads to an increase in the specificity of the test, but simultaneously to a decrease in its sensitivity. If it is advisable to mitigate the test requirements, the boundary between the 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 (diseases of diseases). This increases the sensitivity of the method, but its specificity is reduced.

Thus, conducting diagnostic studies and evaluating their results quantitatively, the doctor is always in the conditions of choice: it sacrifice sensitivity to increase specificity, then, on the contrary, prefers specificity by reducing sensitivity. How to act in each case, depends on many factors: the social significance of the disease, its nature, the state of the patient and, not less important - from the psychological characteristics of the doctor's personality.

It follows the most important conclusion for modern medical diagnostics. A quantitative mathematical method, no matter how much the mathematical apparatus or technical meansHis results always have limited, applied importance, obeying the logical thinking of the doctor and correlated with a specific clinical and social situation.

The theory of evidence-based medicine showed that the distinction of groups of patients at the state of health to the norm and pathology conventionally and depends on the point of separation of these states, depending on the subjective qualities of the researcher, its determination or caution, as well as from other prerequisites - external and internal. In fig. 9.2 Presented a coordinate system reflecting decision-making in medicine. The ordinate axis is an incidence rate, and the abscissa axis is the adoption of diagnostic solutions, i.e. . It is noteworthy that the curves of the Poisson distribution, reflecting the totality of norm and pathology, mutually layered on each other. This forms the graphical distribution of correct and erroneous solutions in diagnostics - both positive and negative: accurate gets, skipping, false alarms.

Fig.9.2. Communication between test results and decision-making criteria. IP - True positive results,

IO - Truly negative, LP - false positive, lo - falsely negative

Point X on the axis of decision-making is a point of separation of results for positive and negative. To the left of this axis there are properly negative solutions and diseases of the disease, to the right of the axis - properly positive solutions and false alarms. The relationship of these indicators forms graphic representation On the operational characteristics of the research method. The characteristic features of the identity of the doctor are imposed on this picture. If the doctor is careful, the axis of decision making is shifted to the left, if decisive is right. The relationship of the operational characteristics of the diagnostic test applied accordingly. The interval D denotes the value of the disease recognition criterion.

About the operating system "WINDOVS" knows every computer user. Today, it is considered the most common, simple and convenient, oriented and beginner, and on the "advanced" owner. In this article, we offer the reader briefly get acquainted with all the operating systems of the Windows family systems, ranging from the very first and ending with the most modern. Imagine basic information, distinctive features of versions.

About MS Windows

Windows - "windows". So the name of the popular OS translates into Russian from English.

MS Windows is the name of the family of proprietary operating families of Microsoft, which are focused on using the graphical interface when controlling. It must be said that the initial "windows" was only a graphic superstructure for MS-DOS.

In August 2014, Net Application undertook a large-scale statistical study. According to its results, it was revealed that 89% of personal computers in the world work with the Windows Operations Systems. Agree, a significant indicator.

Today, Windows has functions on platforms x86, x86-64, Ia-64 and ARM. Previously, there were versions for Dec Alpha, MIPS, PowerPC and SPARC.

OS development

The first versions of the Windows family operating systems, as we have said, were not a full-fledged OS. This tincture to MS-DOS. Such a multifunctional extension added new processor operation modes, support for multitasking operations, standardization of computer hardware interfaces, uniform programs for users. This feature concerns the following versions:

A new stage of development - the Windows 9x: 95 and 98, 2000 family, IU.

The modern step of development falls for 2001-2016. His beginning is the issue of two versions of the popular "Windows XP" - corporate and "home". Then the versions "Vista", 7, 8, 10 were presented.

Consider each variation of OS. More.

Windows 1.0.

We will reveal the features of the Windows family system. This version was a "Microsoft" graphical interface for MS-DOS. The principle of the framework manager of the windows was used here. Helped the dialogue with the operating system, unified appearance Programs, optimized work with peripherals.

Bill Gates officially announced the development in 1983 in New York. Over by creating Windows 1.0 worked 24 scientists. In retail sale, the interface arrived two years later - in 1985. In the US, the product cost 99 dollars, and in Germany - 399 brands.

One of the most significant minuses of development: for its use, it was necessary to purchase expensive components - a new processor model, mouse, volumetric memory for a computer.

Windows 2.0.

This replenishment of the MS Windows operating systems family saw the light in 1987. It was distinguished by new features and capabilities:

  • Using speed intel processor 286.
  • Opportunities for memory expansion and interaction of applications with DDE.
  • Applying combinations of hot keys.
  • Using a multi-color environment.
  • Own API code.

Despite all of the above, this operating system did not become widespread, although there were developers who have written programs under it. Its substantial disadvantages: weak hardware, large software limitations.

Windows 3.0.

The main characteristics of the Windows family system: this is the first product that has really received mass distribution. Its release began in 1990. It was explained by the fact that the OS was installed by manufacturers for sold computers.

The MS-DOS file shell in this version was replaced by the "Program Manager". It also used its own superstructure: "File Manager" used to navigate the disk.

Exterior design can be allocated. The interface was pseudochmer: this was achieved by an extended VGA color palette. In this version, a full-featured "control panel" was already. It allowed to operate the system settings and opened a completely new opportunity - use the image as a desktop substrate.

The user assistance system was organized using HTML language, already contained hyperlinks. Advanced has a set of related software:

  • WordPad text editor.
  • Graphics editor Paintbrush.
  • Games "Solitaire-Free Cells", "Solitaire Kosyanka", "Supper".
  • Other utilities.

Multiple memory modes were maintained: 16- and 32-bit. According to users, in terms of the convenience of OS, it was equal with the modern products of Apple Macintosh.

Windows 3.1.

What is the advantage of the family operating system Microsoft Windows. version 3.1? This is the first OS from a corporation that has the support of the Russian language, which is why gained widespread in Russia.

Released to the market in 1992. Some distinctive features There is no - 3.1 was an improved version of the previous release. Admitted the advanced settings of the working medium, improved the graphical interface, corrected errors and increased the stability of the work.

Windows 95.

The code name of this graphics operating system of the Windows family - "Chicago". It was released in August 1995 (version for Russia is presented in November of the same year).

Mainly intended for home computers. It was hybrid: supported 16- and 32-bit systems. It was here that the desktop appeared with the icons familiar to us, the taskbar and the "brand" menu "Start".

Windows 98.

The official release (after beta testing) of this version came in 1998. We list the main features, the characteristics of the Windows family system:

  • Improved AGP support.
  • Modified drivers for USB.
  • Support operation of a system with multiple monitors.
  • First internet Browser Explorer.
  • Support Web TV.

In 1999, an updated version of the OS was released. It was distinguished by a more advanced browser, adding support for DVD.

Windows 2000 and me

The version was released, respectively, in 2000. It was characterized as follows:

  • Updated interface.
  • Support for the Active Directory directory service.
  • NTFS 3.0 file system.
  • IIS, presented in version 5.0.

In the same 2000, a new version of the system is Windows ME (MILLENNIUM EDITION). Briefly imagine what it was different:

  • Improved working with multimedia means.
  • The ability to record both audio and video conferencing.
  • The emergence of means to restore information after system failures.
  • No real mode from MS-DOS.

Windows XP and Vista

XP is the most popular operating system from the group "WINDOVS". He had a version for both home and corporate computers. Key additions:

  • Improved graphical interface.
  • Fast change of "users".
  • The possibilities of remote PC management.
  • Improving system recovery capabilities.

In 2003, I saw the Light Server OS - Windows Server 2003. According to its developers, much attention was paid to the security of the system. In 2006, a version of XP for low-power PC called Windows Fundamentals For Legacy PCS (FLP) appeared.

In 2006, "Vista" was represented by corporate clients. Private users were able to purchase her "home" version only in 2007. "Vista" distinguished the following:

  • New user interface management features.
  • Updated memory management subsystem, I / O.
  • The appearance of the "hibernation" mode.
  • Improving security features.

Windows 7.

This operating system from Windows appeared on store shelves in 2007. Let's look at its distinctive features:

  • Support "Unicode 5.1".
  • The possibility of multitouch control.
  • The appearance of 50 new fonts in addition to the modified standard.
  • Support for folder pseudonyms at the internal level.
  • Close integration with drivers manufacturers.
  • Compatibility with a number of old applications whose launch was impossible on the "Vista".
  • New interface standard multimedia player.
  • Support multiple monitors, multimedia extensions, the ability to play audio files with low delays.

Windows 8.

This version was on sale in 2012. According to statistics, it is in second place in the world (after the 7th version).

Innovations here are as follows:

  • Log in with account "Microsoft".
  • Two new methods for user authentication.
  • Appendix app stores for OS.
  • A new version Internet browser: in the desktop and sensory version.
  • The ability to restore and reset the system.
  • New "Task Manager".
  • The appearance of the "Family Security" option.
  • New control panel, changing the greeting screen.
  • Advanced search system.
  • Convenient switching keyboard layouts.

Windows 10.

The newest version of the operating system was published in July 2015. Here is its key differences from the previous ones:

  • Modification of the "Start" menu: presented in the form of custom tiles customizable.
  • Changing the size of the "start".
  • New features of application store application.
  • The appearance of the "Notification Center".
  • Updated calendar, clock, battery indicator (for laptops).
  • Modern windows with new animation.
  • Updated Greeting and Lock Interfaces.

This ends our overview of Windows operating systems. Perhaps already in the near future the list is added by the new version.

Operating system (OS) is a program of programs that ensures control of computer resources and processes that use these resources when calculating. Process - This is a sequence of actions prescribed by the program. Resource - This is any logical or hardware component of the computer. The main resources are the processor time and RAM. Resources can belong to one or more external computers to which the operating system refers using the computing network.

Resource Management It consists of two functions: simplify access to the resource and the distribution of resources between competing processes. To solve the first task, operating systems support custom and Software interfaces . To solve, the second operating systems use various virtual memory and processor control algorithms.

OS Characterized by basic signs:

· The number of users simultaneously served by the system (single-user and multiplayer);

· The number of simultaneously performed processes (single-handed and multitasking);

· The type of computing system used (single-processor, multiprocessor, network, distributed).

Example.The Windows98 operating system is multi-tasking, Linux - multiplayer, MS-DOS single and, therefore, single-user. Windows NT and Linux operating systems can support multiprocessor computers. The Novell NetWare operating system is network, built-in networks also have Windows NT and Linux.

Custom and software interfaces.To simplify access to computer resources, operating systems support user and software interfaces. The user interface is a set of commands and services that simplify the user with the computer. The program interface is a set of procedures that simplify the programmer computer control.


Fig. 1. Operating system interfaces

Example.Windows provides the user with a graphical interface that represents (from the user's point of view) a set of rules for a visual control computer. In addition to the main graphical interface, the user also provides a command interface, that is, a set of commands of a particular format. To do this, in the system menu there is an item "Run". A set of system functions in Windows is called API (Application Programming Interface). In this set there are more than a thousand procedures for solving different system tasks. The Linux operating system also has two features for computer management, but, as a rule, preference is given to the commands.

Processor time and organization of memory.To organize a multi-tasking OS mode, it must in some way distribute the time of operation of the processor between simultaneously working programs. Typically, the so-called displacing multitasking mode is used. When displacing mode, each program continuously operates for a strictly defined period of time (time quanta), after which the processor switches to another program. Since the quantum of time is very small, then with sufficient processor performance, the illusion of the simultaneous work of all programs is created.

One of the main tasks of the operating system is to manage memory. When the main memory is missing, all data that is not currently used is written to a special paging file. The memory presented by the paging file is called external page memory. The totality of the main and external page is called virtual memory. However, for the programmer, the virtual memory looks like a single whole, that is, it is considered as an unordered set of bytes. In this case, it is said that a linear memory addressing is used.

Example.Windows and Linux operating systems use linear virtual memory addressing. The MS-DOS operating system used a non-linear addressing of the main memory. The main memory had a complex structure that had to take into account when programming. MS-DOS swap files are not supported.

Structure of the operating system.Modern OS, as a rule, have a multi-level structure. Directly with equipment works core operating system. The kernel is a program or a set of connected programs that use computer hardware features. Thus, the kernel is a machine-dependent part of the operating system. The kernel defines the program interface. At the second level, there are standard operating system programs and a shell that work with the kernel and provide a user interface. Second-level programs are trying to make machine-independent. Ideally, the core replacement is equivalent to replacing the version of the operating system.


Fig. 2. Linux operating system levels

File system.Any data is stored in external memory EUM in the form of files. Files need to be managed: Create, delete, copy, change, etc. Such to the user in the form of user and software interfaces provides OS. The way of organizing files and manage them is called the file system. The file system determines, for example, which characters can be used for the file name, what is the maximum file size, which is the name of the root directory, etc. The method of organizing files affects the speed of access to the desired file, to the security of file storage and others.

The same OS can work simultaneously with several file systems. As a rule, the function of the file system is implemented by means of the operating system kernel.

Example.For PEVM uses several types of file systems:

FAT16 - used in Windows95, OS \\ 2, MS-DOS;

FAT32 and VFAT - used in Windows95;

NTFS - used in Windows NT;

HPFS - used in OS \\ 2;

Linux Native, Linux Swap - Used in Linux OS.

FAT file system is most simply arranged. The name of the root catalog always has the form: A: \\, Q: \\, C: \\, etc. The file name consists of three parts: path, actually name, expansion. The path is the name of the directory in which the file is located. The extension indicates the type of file. For example, the full file name C: \\ Windows \\ System \\ Gdi.exe, path - C: \\ Windows \\ System \\, Expansion - EXE, Actually Name - GDI. According to the FAT rules, the file name itself may contain from 1 to 8 characters, and the name extension separated on behalf of the point is up to 3. When named files, capital and lowercase letters do not differ. The full file name includes the name of the logic device on which the file and the catalog name is located in which the file is located. The system stores information about the size of the file and the date of its creation.

VFAT data organization reminds FAT. However, it allows you to use long file names: Names up to 255 characters, full names up to 260. The system allows you to store the last file to access, which creates additional features To combat viruses.

The file system can be implemented in the form of a driver with which all programs read through the operating system are communicating or recorded information to external devices. The file system may include information storage facilities. For example, file nTFS system It has automatic error correction and replacement of defective sectors. The special mechanism monitors and records all actions performed above the magnetic discs, so in the event of a failure, the integrity of the information is restored automatically. In addition, the file system may have means to protect information from unauthorized access.

Model "Client-server".An important feature of modern operating systems is that the "client-server" model is based on the interaction of the application program. All contacts of the user program (client) to the OS are processed by a special program (server). It uses a mechanism similar to the call to the remote procedure, which makes it easy to move from the interaction between the processes within one computer to the distributed system.

Technology "Plug and Play".Under the technology "Plug and Play" (PNP-technology) means a way to interact between the OS and external devices. The operating system conducts a survey of all peripheral devices and should receive a certain response from each device, from which you can determine which device is connected and which driver is required for its normal operation. The purpose of using this technology is to simplify the connection of new external devices. The user must be relieved of difficult work on setting up an external device that requires high qualifications.

Service systems - software product, changing and complementing user and software interfaces OS. Service systems differ on operating environments, shells and utilities.

Operating environment - system, changing and complementing both user and software interface. The operating environment creates an illusion of work in a full-fledged OS for users and application programs. The appearance of the operating environment usually means that the operating system used does not fully meet the requirements of the practice.

Fig. 3. The role of the operating environment

Protection of information - This is a very big problem. As part of the operation of the OS, under the protection of information, it is implied mainly to ensure the integrity of information and protection against unauthorized access. Ensuring integrity is placed mainly on the file system, and protection against unauthorized access is on the kernel. The usual mechanism of such protection is the use of passwords and privilege levels. For each user, the boundaries of access to files and priority of its programs are determined. The highest priority has a system administrator.

Networks and distributed systems.An integral part of modern OS is funds that allow them to communicate through a computing network with applications running on other computers. For this, OS solves mostly two tasks: ensuring access to files on remote computers and the ability to start the program on a remote computer.

The first task is most naturally solved by using the so-called network file system, which organizes the user with remote files So, as if these files are on the user's magnetic disk.

The second task is solved using the mechanism for calling a remote procedure, which is implemented by the core tools and also hides the difference from the user between local and remote programs.

The presence of means for managing resources of remote computers is the basis for creating distributed computing systems. Distributed computing system is a combination of several related computers working independently, but perform a common task. Such a system can be considered as multiprocessor.

Shell - System changing user interface. The shell creates an interface for the user, different from the operating system itself. The task of the shell is the simplification of some commonly used actions with the operating system. However, the shell does not replace the OS, and therefore the professional user must also study the command interface itself.

Utilities They have a highly specialized assignment and perform each function. Utilities are performed in the environment of the respective shells and provide users. additional services (mainly for maintenance of disks and files). Most often it is:

Disk maintenance (formatting, ensuring the safety of information, the possibility of its recovery in case of failure, etc.);

Service file and directories (search, view, etc.);

Creating and updating archives;

Providing information about computer resources, on the employment of disk space, on the distribution of RAM between programs;

Printing text and other files in various modes and formats;

Protection against computer viruses.

Fig. 4. The role of the shell

Tool systems - This is a software product that provides for the development of information and software. Tool systems include: programming systems, quick application development systems and database management systems (DBMS).

Programming system Designed to develop applications using a certain programming language. It includes:

· Compiler and / or interpreter;

· Relations editor;

· development environment;

· Library of standard subroutines;

· Documentation.

The compiler is a transformation program. source program In the object module, that is, a file consisting of machine commands. The interpreter is a program that directly performs the instructions of the programming language.

The link editor is a program that collects multiple object files to one executable file.

Integrated development environment is a set of programs that includes a text editor, program management file management tools, program debugger, which automates the entire program development process.

Library of standard subroutines - a set of object modules organized into special files that are provided by the programming system manufacturer. In such libraries, there are usually subprograms of I / O files, standard mathematical functions, file management programs. Object modules from the standard library are usually automatically connected by the link editor to user object modules.

Fig. 5. Stages of program development

Quick Application Development Systems represent the development of conventional programming systems. In RAD systems, the programming process itself is largely automated. The programmer does not write the text of the program itself, and with some visual manipulations, it indicates the system which tasks must be performed by the program. After that, the RAD system itself generates the text of the program.

Database Management System- This is a universal software tool intended for organizing the storage and processing of logically interconnected data and provide quick access to them. One of the important features of the computer is the storage and processing of large amounts of information, and not only text and graphic documents (drawings, drawings, photos, geographical maps), but also the web pages of the global Internet, sound and video files, take place on modern computers. Creating databases ensures data integration and the ability to centrally manage them. In the database, information organized by defined rules that provide for general principles Descriptions, storage and manipulation of data, in order to work with them various users and programs.

The DBMS enable for programmers and system analysts to quickly develop more advanced data processing software, and end users to directly manage data. The DBMS should provide the user to the user search, modify and save data, operational access, data integrity protection from hardware failures and program errors, delimitation of rights and protection against unauthorized access, supporting the collaboration of multiple users with data. There are universal database management systems used for various applications. When configuring universal DBMSs for specific applications, they must have appropriate means. The process of setting up the DBMS to a specific scope is called the generation of the system. The universal DBMS includes, for example microsoft systems Access, Microsoft Visual Foxpro, Borland Dbase, Borland Paradox, Oracle.

Telecommunication data processing technologies.An important feature of many OS is the ability to interact with each other, through the network, which allows computers to interact with each other, both within the framework of local computing networks (LAN) and in the global Internet.

Modern operating systems, both newly created and updated versions of existing, support a complete set of protocols for working in local and global computer networks. At the moment, the global computer industry develops very rapidly. The performance of systems increases, and therefore the possibilities of processing large volumes of data increase. MS-DOS class operating systems no longer cope with such a data stream and cannot entirely use the resources of modern computers. Therefore, it is not widely used anywhere else. Everyone is trying to go to the more advanced OS, what are UNIX, Windows, Linux or Mac OS.

If you give the definition of the user words, then operating system You can call the most important program that is loaded first when the computer is turned on and due to which communication is becoming possible between the computer and man. The task of the OS is to provide the convenience of working with a computer for a person user. OS manages all devices connected to a computer, providing access to other programs. In addition, the OS is a kind of buffer transmitter between computer glands and other programs, it takes on signals-commands that send other programs, and "translates" them to understand the language of the machine.

It turns out that each OS consists of at least three mandatory parts:

First - core , command Interpreter , "Translator" from the software to "Iron", the language of machine codes.

Second - specialized programs for managing various devices that are part of the computer. Such programs are called drivers - i.e. "drivers" managers. This also includes the so-called "system libraries", used both the operating system itself, as well as in its composition program.

And finally, the third part is a comfortable shell with which the user communicates - interface . A kind of beautiful wrapper in which the boring and not interesting for the user is packed. The packaging comparison is successfully also because it is to pay attention to when choosing an operating system, - about the kernel, the main part of the OS, recalls already. Therefore, such an unstable and unreliable in terms of the OS kernel, like Windows 98 / Me, and used such stunning success - thanks to a beautiful wrapping interface.

Today, the graphical interface is a constant attribute of any operating system, whether Windows XP., Windows NT or Mac OS (operating system for computers apple Macintosh). The operating systems of the first generations had no graphic, but a text interface, i.e. the commands of the computer were not given by clicking the mouse in the pictogram pattern, but by entering commands from the keyboard. For example, today to run the editing program microsoft texts Word is enough to click on the icon of this program on the Windows desktop. And earlier, when working in the previous generation OS - DOS, it was necessary to enter the type command

C: \\ Word \\ Word.exe MyBook.doc.

OS are classified by:

· The number of simultaneously working users: single-user (intended for servicing one client) and multiplayer (designed to work with a group of users at the same time behind different terminals). An example of the first can serve as Windows 95/98, and the second is Windows NT. For home use you will need a single-user OS, and for the local office network or enterprise you need a multiplayer OS;

· The number of processes simultaneously performed under the control of the system: discharged , multitasking. Overbalanced operating systems (DOS) can be performed at the same time no more than one task, and multitasking OS are capable of maintaining parallel execution of several programs that exist within one computing system, making a computer power between them. For example, the user can enter text in document Word., listening to music from your favorite CD, and the computer at the same time will copy the file from the Internet. In principle, the number of tasks that your OS can perform is not limited to anything, except for the power of the processor and the capacity of RAM;

· The number of supported processors: single-processor , multiprocessor (support the mode of distribution of resources of several processors to solve this or that task);

· The discharge of the operating system code:

Ø 16-bit (DOS, Windows 3.1),

Ø 32-bit (Windows 95 - Windows XP),

Ø 64-bit (Windows Vista.);

The discharge of the OS cannot exceed the discharge of the processor;

· Type of interface: team (Text) and object-oriented
(as, rule, graphic);

· Type of user access to computers:

Ø with batch processing - from programs to be executed, a package of tasks entered into the computer and executed in order of priority with possible prioritization),

Ø with division - Provides simultaneous dialog (interactive) mode of access to the computer of several users on different terminals, which are elapsed by the machine resources, which is coordinated by the OS in accordance with the specified service discipline),

Ø real-time - Provide a specific guaranteed time response time to a user's request to manage them with any external in relation to computer events, processes or objects. OS RV is mainly used in the automation of areas such as the production and transportation of oil and gas, the management of technological processes in metallurgy and mechanical engineering, chemical proceedings, water supply, energy, robot management. Of these, the QNX RV RV is highlighted with its full set of instrumental tools to which the user is used to, working with the UNIX OS.

· Type of resource use: network, local . Network OSs are designed to manage computer resources combined into the network for sharing data, and provide powerful means of distinguishing data access to data as part of ensuring their integrity and safety, as well as many service capabilities using network resources. In most cases, network OS are installed on one or more sufficiently powerful servers computers allocated exclusively for network maintenance and shared resources. All other OS will be considered local and can be used on any personal Computerconnected to the network as a workstation or client.

Finally, still division - specialization , purpose of a particular OS. After all, no matter what the individual leaders of a separate software corporation speak, universal operating systems do not exist. One more suitable for networking, the other will choose programmers, third - home users. As practice shows, the knowledge of one OS in our time is by no means enough. In your professional work, you will probably have to face not only with Windows, but also with other OS - and it is necessary to prepare for this in advance.

Machine-dependent properties of the OS are:

· Processing of interrupts;

· Process planning;

· Input management-output;

· Governance real memory;

· Virtual memory management.

Machine-independent properties of OS are:

· Working with files;

· Ways to plan user jobs;

· Organization of parallel operation of programs;

· Distribution of resources;

· Protection.

The main criteria approach when choosing an operating system.There is a large number of OS and the user must determine which OS is better than others (for one or another criteria). To choose one or another OS, you need to know:

· On which hardware platforms and at what speed operates OS;

· What peripheral hardware provision is supported;

· How fully satisfies the user needs, i.e. What are the functions of the system;

· What is the method of interaction between the OS with the user, i.e. How prominent is convenient, the user interface is understandable and used;

· Are informative tips, built-in directories, etc.;

· What is the reliability of the system, i.e. its resistance to user errors, equipment failures, etc.;

· What opportunities provides an OS to organize networks;

· Does OS provide compatibility with other OS;

· What instrumental tools have an OS to develop applied programs;

· Is the support of various national languages \u200b\u200bin OS;

· What famous application packages can be used when working with this system;

· How is it carried out in the protection of information and the system itself.

Computer science - Operating system (OS.) - The main tasks of the OS. - User Interface - Characteristics, shell

The operating system (OS) is a set of software tools to manage computer hardware resources, support program execution, interaction of programs with hardware, other programs and users.

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

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

The situation when the program developed for one operating system can be carried out in the environment of the other OS directly, it becomes infrequently. More often software products oriented on some particular OS cannot function in an environment of another OS (software incompatibility).

The main purpose of the operating system is the relationship between software products and the "hardware" of the computer. The operating system makes programs to a certain extent independent of the specific modification of the machine and installed on it equipment. She also allows you to "say" to the user what he wants from the computer.

The operating system adopted some agreements and restrictions acting in order for it to "understand" the user's desires. The dialogue with the operating system is something like a conversation with a stupid, incomprehensible, but executive servant. She understands you only when you tell her where it lies and what should I do with it, and if you say it inaccurately, then she can do something completely different or refuse to do anything at all.

The main tasks of the OS.

1. Support for programs; ensuring their interaction with the hardware and each other;

2. Distribution of resources (processor time, RAM, disk space, etc.); organization of the file system (data storage system on external media information); Accounting for the use of resources, video control;

3. Processing erroneous situations; protection of information;

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

5. Network support.

User Interface

In addition to managing resources and support the operation of the OS programs, represents the user the ability to manage the computer in the dialogue mode. This happens with the user interface.
The user interface is a component of a software product that provides dialogues between the program and the user.

The simplest variety of IP - interface command line. It involves managing the computer by entering commands from the keyboard.

A bright example serves a command line in MS-DOS:

C: \\ Users \\ Diplom \\\u003e Copy Head.htm C: \\ Users \\ Bakalavr

1 File copied

The more convenient view of the IP is a text window interface. It does not require a set of commands on the keyboard, and controls the control to press individual keys or the mouse buttons when the control action is selected in the menu and dialog boxes.

An example is the Borland Pascal tool envelope:

The most modern is the graphic window interface connecting the developed window interface dialogs (menu systems, dialog boxes, toolbars, pictograms, etc.) with large image graphic capabilities.

An example is the "My Computer" folder window:

----

Characteristics of OS.

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

2. The number of programs simultaneously performed under the control of OS (one - and multitasking OS).
Multitasking OS support parallel execution of several programs that work within one computing system at one point in time. Multitasking is corporate and displacing.
In the presence of corporate multitasking of the application, the processor shared, periodically transmitting it to each other. If some application refuses to free the processor, the system can do nothing with it.
If the multitasking is used, the operating system fully controls all applications and distributes the processor time between them, thereby much lowering the likelihood of the "freezing" system in errors in the operation of programs.
Single-handicap OS support the execution mode of only one program at a separate point of time;

3. Multipleness is a technology that allows the application to properly implement the multitasking performance of its processes. The process is any task or activity initiated by the program. One program can perform several processes at the same time;

4. User Interface Type: Command Line Interface, Text Window Interface, Graphic Window User Interface (X, Type, Light);

5. requirement for hardware resources;

6. Performance;

7. Reliability (sustainability in the work, data protection from unauthorized access);

8. Provision of application programs;

9. Availability network features (Network, Local OS);
Network OSs are designed to manage computer resources, combined into a network for sharing data, and provide powerful means of delimiting data access when providing their integrity and safety, as well as many service capacity to use network resources;

10. The number of supported processors: single-processor, multiprocessor;
Multiprocessor OS, in contrast to single-processor, support the use of multiple processors to solve one task;

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

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

The most common OS for computer

The main characteristics of operating systems are:

The first representative of this family is the system MS- DOS. (Microsoft Disk Operating System Disk Operating System Microsoft) was released in 1981 due to the advent of IBM PC.
The operating systems of the DOS family are one-shifted 16 discharge and possess the following features:

Command line interface
Modular structure that simplifies the transfer of the system to other types of computer
A small volume available without special means of RAM (640 KB)
Low hardware requirements, large scope of application programs.

The significant disadvantage of the DOS family operating systems 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 OC Windows 95.

MS-DOS initial information

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

The operating system bootloader is a small program stored in the first sector of any system diskette (floppy disks recorded on it operating system) or hard drive that loads two system File io.sys and msdos.sys. It is the boot of the operating system that transmits the BIOS control at the initial start of the machine.

IO.SYS and MSDOS.SYS files are constantly in the computer's memory: io.sys exercises an addition to the basic I / O system, depending on the needs of this version of the operating system, A 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) serves the operation of the system with the user. He himself performs part of the operating system commands (these commands are called internal), and when calling external commands or execute other programs, it transmits it to them, at the end of their work again takes control over and unloads the spent program from memory.
External operating system commands 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), connecting additional equipment (say, mice) and ensuring the normal operation of non-standard devices.

Consider now the principles of organizing storing information in the computer.

Shell operating systems

The shell is called the superstructure over the operating system, which is significantly facilitated by the user and providing a number of additional service services.

Shells of operating systems provide:

* Creating, renaming, copying, shipping, deleting and quickly searching for a file in the current disk directory or on all computer discs;
* View, create and compare directories;
* View, create and edit text files;
* Archiving, update and unzip archive files and view archives;
* synchronization of directories, splitting and merging files;
* Support communication between two computers through serial or parallel ports;
* Formatting and copying diskette, change the label of floppy disk and Tom labels for hard disks, as well as cleaning disks from unnecessary files;
* Running programs.

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

The dos navigator sheath completely copies the original NC idea, but has additional functions. It supports work with a large number of archivers, allows you to highlight the files of different types of color, has more convenient tools for intercomputer communication via the modem.

Graphic shells for Windows - Dash Board for windows, Dash Board for Windows 95, DeskBar 95 for Windows 95 - allow the user to quickly create menu of launching programs and call documents, as well as monitor the use of system resources.

Shet shells and RAR are designed to control compression (archiving) and unpacking files in the MS-DOS environment. Winrar and WinZir shells are designed to control compression (archiving) and unpacking files in a graphics environment. NDOS shells, Norton Desktop for Windows are designed to manage files.

Publication date: 10/01/2010 10:34 UTC

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