Computer science - Operating system (OS) - Main tasks of the OS - User interface - Characteristics, shells. List of operating systems: features, characteristics and reviews

Page table organization is one of the key elements displaying addresses in page and segment-page schemes. Let us consider the structure of the page table for the case of page organization in more detail.

So the virtual address consists of virtual number pages and offsets. The entry number in the page table corresponds to the number virtual page. The record size varies from system to system, but is most often 32 bits. From this entry in the page table, the frame number for this virtual page is found, then the offset is added and the physical address is formed. In addition, the page table entry contains information about the page attributes. These are presence and protection bits (for example, 0 – read/write, 1 – read only...). The following can also be specified: a modification bit, which is set if the contents of the page are modified and allows you to control whether the page should be rewritten to disk; link bit, which helps highlight little-used pages; cache enable bit and other control bits. Note that page addresses on disk are not part of the page table.

The main problem for efficient page table implementation is the large size of virtual address spaces. modern computers, which are usually determined by the bit size of the processor architecture. The most common today are 32-bit processors, which allow the creation of virtual address spaces of 4 GB in size (for 64-bit computers this value is 264 bytes). In addition, there is the problem of display speed, which is solved by using the so-called associative memory.

Let's calculate the approximate size of the page table. In a 32-bit address space with a page size of 4 KB (Intel) we get 232/212=220, that is, approximately a million pages, and in 64-bit even more. Thus, the table should have approximately a million rows (entry), with an entry per row consisting of several bytes. Note that each process needs its own page table (and in the case of a segment-page design, it is desirable to have one page table per segment).

It is clear that the amount of memory allocated to page tables cannot be so large. In order to avoid placing a huge table in memory, it is divided into a number of fragments. IN RAM store only some fragments of the page table necessary for a specific moment of execution. Due to the locality property, the number of such fragments is relatively small. There are different ways to break a page table into pieces. The most common way of partitioning is to organize a so-called multi-level page table. As an example, consider a two-level table with 4 KB pages, implemented on the 32-bit Intel architecture.

A table consisting of 220 rows is divided into 210 second-level tables of 210 rows each. These second level tables are combined into general structure using one first-level table consisting of 210 rows. The 32-bit address is divided into a 10-bit p1 field, a 10-bit p2 field, and a 12-bit offset d. Field p1 points to the desired row in the table of the first level, field p2 to the second, and field d localizes the desired byte within the specified page frame (Fig. 8).

Figure 8 – Example of a two-level page table

With just one second-level table, you can cover 4 MB (4 KB x 1024) of RAM. Thus, to accommodate a process with a large amount of occupied memory, it is enough to have one first-level table and several second-level tables in RAM. Obviously, the total number of rows in these tables is much less than 220. This approach naturally generalizes to three or more table levels.

Having multiple levels naturally reduces the performance of the memory manager. Despite the fact that the sizes of the tables at each level are selected so that the table fits entirely within one page, accessing each level is a separate access to memory. Thus, address translation may require multiple memory accesses.

The number of levels in the page table depends on the specific architecture. Examples of implementation of single-level (DEC PDP-11), two-level (Intel, DEC VAX), three-level (Sun SPARC, DEC Alpha) paging, as well as paging with a given number of levels (Motorola) can be given. The MIPS R2000 RISC processor operates without a page table at all. Search here desired page, if this page is not in associative memory, the OS must take over (so-called zero level paging).

Introduction

A computer is a computing system consisting of hardware and software. Its operation requires basic software - an operating system. Without an operating system, a computer cannot work.

An operating system is a set of programs that organize and control the operation of a computer.

Purpose of the work: conduct a comparative analysis operating systems Windows and Mac OS families.

Tasks:

• Define an operating system;
• Consider the functions of operating systems;
• Carry out comparative analysis operating systems.

1. Basic definitions and concepts

1.1. operating system

An operating system is a complex of interconnected system programs, which are loaded when the computer is turned on and are permanently stored in the computer's memory. They conduct a dialogue with the user, manage the computer, its resources (RAM, disk space, etc.), and launch other (application) programs for execution. The operating system provides the user and application programs with a convenient way to communicate (interface) with computer devices.

The main reason for the need for an operating system is that the elementary operations for operating computer devices and managing computer resources are very low-level operations, so the actions that are required by the user and application programs consist of several hundred or thousands of such elementary operations.

For example, a magnetic disk drive “understands” only such basic operations as turning on/off the drive motor, installing read heads on a specific cylinder, selecting a specific read head, reading information from a disk track into a computer, etc. And even to perform such a simple action as copying a file from one floppy disk to another (a file is a named set of information on a disk or other machine media), it is necessary to perform thousands of operations to run disk drive commands, check their execution, search and process information in tables placing files on disks, etc.

The operating system hides all these complex and unnecessary details from the user and provides him with a convenient interface to work with. It also performs various auxiliary actions, such as copying or printing files. The operating system loads all programs into RAM, transfers control to them at the beginning of their work, performs various actions at the request of executing programs, and frees RAM occupied by programs when they complete.

Operating systems can be divided into groups (classified) according to the following criteria:
1. By the number of users: single-user operating system (serves only one user); multi-user (works with many users)
2. By the number of processes: single-task (process only one task - no longer used); multitasking (locates several tasks simultaneously in RAM, which are alternately processed by the processor)

By type of funds computer technology: uniprocessor, multiprocessor (tasks can be performed on different processors; servers are usually multiprocessor), network (provide sharing resources for all tasks performed on the network).

Based on the type of interface (the method of interaction with the user), operating systems are divided into 2 classes: OS with a command line interface and OS with a graphical interface.

There are several types of operating systems: Windows, Mac OS.

1.2. Operating system features

The functions of the operating system include:

• carrying out a dialogue with the user;
• input/output and data management;
• planning and organizing the program processing process;
• resource distribution (RAM and cache, processor, external devices);
• launching programs for execution;
• all kinds of auxiliary maintenance operations;
• transfer of information between different internal devices;
• software support for the operation of peripheral devices (display, keyboard, disk drives, printer, etc.).

2. Comparative analysis of operating systems

2.1. Windows XP

The history of Windows (developed by Microsoft) dates back to 1986. It gained popularity in 1990, when Windows 3.0 was released. The popularity of the new version of Windows was due to several reasons. The graphical interface allows you to work with objects on your computer not with the help of commands, but with the help of visual and understandable actions on the icons representing these objects. The ability to simultaneously work with several programs has significantly increased the convenience and efficiency of work. In addition, the convenience and ease of writing programs for Windows has led to the emergence of an increasingly diverse range of programs running under Windows control. Finally, work with a variety of computer equipment, which also determined the popularity of the system. Subsequent versions of Windows were aimed at improving reliability, as well as support for multimedia (version 3.1) and work in computer networks (version 3.11).

In 1995, Windows 95 appeared, which became a new stage in Windows history: The interface has changed significantly, the speed of programs has increased, and the Internet Explorer browser has been included in the system.

The continuation of the development of Windows 95 was the operating system that appeared in 1998 (Windows 98). While the interface remained the same, the internal structure was significantly redesigned. Much attention was paid to working with the Internet, as well as supporting modern information transfer protocols - standards that ensure the exchange of information between various devices. In addition, a feature of Windows 98 is the ability to work with multiple monitors.

The next step in Windows development was the appearance of Windows 2000 and Windows ME (Millennium Edition - millennium edition). The Windows 2000 system was developed on the basis of Windows NT and inherited from it high reliability and security of information from outside interference. The Windows ME operating system became the successor to Windows 98, but acquired many new features. First of all, this is improved work with multimedia, the ability to record not only audio, but also video information, powerful means of recovering information after failures, and much more.

operating room Microsoft system Windows XP (from the English eXPerience - experience), or Microsoft Codename Whistler, is an OS of the Windows family, created on the basis of NT technology.

Currently Windows time XP for desktops and workstations comes in three versions: Home Edition for home personal computers, Professional Edition for office PCs, and finally Microsoft Windows XP 64bit Edition is a version of Windows XP Professional for personal computers built on a 64-bit Intel Itanium processor with clock frequency more than 1 GHz.

When you compare Windows XP to earlier versions of Microsoft Windows, it's easy to spot many significant differences in the new operating system. Despite the fact that this OS was developed on the basis of the NT platform and, at first glance, its characteristics are in many ways similar to Microsoft Windows 2000, in fact Windows XP belongs to a fundamentally different generation of operating systems of the Windows family. Now the Windows user is not tied to any standard interface installed on the system by default: you can easily change the appearance of windows by downloading any of hundreds of specially designed “Themes” from the Internet. The traditional Main Menu, which provides access to programs installed on the computer, documents stored on disks and operating system settings, has also undergone a number of significant changes. Now, when you press the Start button, a dynamic menu appears containing icons for only the five programs that you use most often. Thanks to this, you can get started with the applications you need much faster. The Log Off and Turn Off Computer buttons are also located here, allowing you to end the current Windows session and turn off the computer.

In the Microsoft Windows environment, the user often has to work simultaneously with several documents or a set of different programs. At the same time, inactive applications are minimized to the Taskbar, as a result of which it sooner or later becomes overcrowded with icons, and switching between tasks becomes difficult. In order to relieve the taskbar and free up more workspace for displaying icons of running applications, Windows XP uses the so-called task grouping algorithm, according to which similar programs running on the computer at the same time are combined into a logical visual group.

Windows has significant security problems in terms of remote hacking of the system. Coping with this problem is partially helped by installing patches regularly released by developers. Then Microsoft products become mostly secure, but without updating, the operating systems may again be open to hackers.

2.2. Mac OS

Go to new architecture, greatly transformed the Mac community and, in fact, divided the understanding of their computers into two eras - “before the transition to Intel” and “after the transition to Intel.”

The first Mac OS appeared in 1984, much earlier than Windows. It was designed specifically for Macintosh (Mac) computers. These computers have a closed architecture, that is, the computers themselves are assembled only by Apple.

The strength of Mac OS is the virtual absence of viruses for Macintosh. And the point is not only that Mac OS is not very widespread compared to Windows, but also that traditional viruses simply do not work in a UNIX environment. Theoretically, of course, there are samples of viruses that can work with some applications for Mac OS, but their number is simply insignificant compared to malicious software written for Windows. Even remote hacking of a computer running Mac OS is much more difficult than hacking a machine running Windows, and anti-virus programs may be needed only to prevent an infected file from being sent to a machine running Windows, since it will not cause you any harm .

The system interface also has significant differences from Windows. For example, if in Windows each program usually corresponds to one window with tabs and toolbars opening in it, then in Mac OS “floating” windows and panels are used, not tied to a common window, but located on the desktop.

Main feature Mac interface The OS is minimalistic. This means that when the application is launched, the user is presented with key, basic interface and control elements and, only as needed, the user can customize the working environment to his liking. In this case, the user will not experience difficulties in mastering the OS interface.

Another distinctive feature of the interface is the dock panel. This is a panel at the bottom of the desktop where you can find icons for files and applications that you need quick access to, as well as running applications. The panel can be edited, resized, removed and added application icons. You can also note interface elements such as Dashboard and Expose. Dashboard is a panel for working with “widgets,” the simplest graphical applications that, as a rule, perform information functions. Expose – a function to display on the screen in the form of thumbnails all open windows or only windows of the active program.

Mac OS, unlike Windows, comes with the necessary set of tools for full operation from the very beginning. And although the list of programs for Mac OS is not as impressive as for Windows, nevertheless, all the main required applications for work and entertainment there are available.

2.3. Advantages and disadvantages of operating systems
Advantages and disadvantages of Windows and Mac OS operating systems

Conclusion

Over the past 10 years, computers have literally flooded apartments, offices, and businesses. The “smart box” is confidently entering our lives. Many people no longer imagine how they could manage without it before .

A large number of users prefer to use the computer for entertainment. In this case, Windows is suitable for people who need a multimedia center (music, cinema, Internet, games). And for those who need a computer that is not expensive and not too difficult to use for work, and Mac OS X is best option for people who want to work on a computer without delving into the features of the system

Municipal educational institution "Gymnasium of Nadym"

Comparison of common operating systems

Completed by: Mikhail Vavilin,

Supervisor: ,

computer science and ICT teacher

1. Introduction……………………………………………………………………………………….2

2. Literature review………………………………………………………………………………..3

3. Practical data………………………………………………………………………………………6

4. Conclusions………………………………………………………………………………………….9

5. References………………………………………………………………………………10

Introduction.

Among all computer programs operating systems occupy a special place with which PC users work. The choice of OS depends on the performance of your work, the degree of data protection, the necessary hardware, etc. However, the choice of operating system also depends on technical characteristics(configuration) of the computer. The more modern the operating system, the more it not only provides more features and is more visual, but also the more demands it places on the computer (processor clock speed, operational and disk memory, availability and capacity of additional cards and devices).

The OS loads all programs into RAM, transfers control to them at the beginning of their work, performs various actions at the request of executing programs, and frees RAM occupied by programs when they complete.

Thus, the choice of operating system is very important, since the entire further work PC: performance, data security, etc.

But you can't just go to the store and buy what you like. In order to make this choice, you first need to familiarize yourself with the system requirements of this product, and then choose the one that suits you best.

Therefore, the goal of our work was presentation and comparison from different angles of the most common operating systems.

1. Consider the system requirements of common operating systems.

2. Familiarize yourself with the choice of most users.

3. Analyze modern operating systems and identify their disadvantages and advantages.

Object of work: operating systems.

Subject of research: comparative analysis of some modern operating systems.

Literature review.

Operating system, OS (English operating system) - a basic set of computer programs of a kind, a transmitter between computer hardware and other programs. The OS takes command signals sent by other programs and “translates” them into a language understandable to the machine. The OS manages all devices connected to the computer, providing access to them to other programs.

The OS allows you to abstract away from hardware implementation details, providing software developers with the minimum required set of functions. From the point of view of ordinary people, ordinary users computer hardware, the OS also includes user interface programs. Main functions (simple OS):

Standardized access to peripheral devices(input/output devices);

RAM management (distribution between processes, virtual memory);

Controlling access to data on non-volatile media (such as Hard drive, CD, etc.), usually using a file system;

User interface;

Network operations, protocol stack support

Every OS consists of at least 3 required parts.

First– core, command interpreter, “translator” from software language to “hardware”, machine code language.

Second – specialized programs to control various devices included in the computer. Such programs are called drivers. This also includes the so-called “ system libraries", used both by the operating system itself and the programs included in it.

Third part is a convenient shell with which the user communicates - the interface. This is a kind of beautiful wrapper in which a boring and uninteresting kernel is packed. The comparison with packaging is also apt because it is what people pay attention to when choosing an OS, while the kernel, the main part of the OS, is remembered only later.

The most common operating systems today are all Microsoft operating systems, Linux and Mac OS.

I will not focus special attention on the Windows OS, since almost anyone who uses a computer probably uses Windows as their desktop operating system. Therefore, let’s immediately move on to the system requirements of this product.

1.Microsoft Windows XP

For quick and stable operation your computer must have a Pentium-II processor, processor frequency from 500 MHz, free disk space at least 2 GB and, accordingly, a disk reader.

2.Microsoft Windows Vista

If you have chosen Vista, then your computer system must be no weaker than the data system requirements: a processor with a clock speed of at least 800 MHz, 512 MB of RAM, 32 MB of video memory, a graphics card that supports DirectX 9, a DVD reader and at least 15 GB of free hard disk space.

3.Microsoft Windows Seven

To run this system, you need a processor with at least a 1 GHz frequency, 1 GB of RAM or higher, more than 16 GB of free hard disk space, a DVD reader, and graphics card DirectX 9 compatible.

Internet access system.

The most delicious target for

malware V

the last few and

the next couple of years.

Service Pack installation required

2 and third-party antiviruses and

firewalls, as well as many

updates and patches for

safe use in

Linux is more secure

system than Windows.

For example, Ubuntu, by -

by default, doesn't even create

administrator account, which

is an essential goal

for malware.

At the heart of Unix - more

strict system, which leads to fewer holes in

security compared to

Windows architecture.

Small

Linux prevalence

leads to hackers

pay less attention to her

attention than on Windows.

The interface is clear, uncluttered and

logical. So good that it

trying to recreate it on others

operating systems using themes

design and special programs.

Translucency and Animation Effects

very organic and helpful

navigate the system.

Availability of virtual desktops

drag-and-drop

windows between tables.

Possibility of using widgets.

Instant search already at

type searches for files and their contents by

throughout the system and on the local network,

supports logical operations And

arithmetic calculations.

Conclusions

1. Microsoft Windows XP

Most likely, you are very familiar with this system. If you are satisfied with everything, then there is no need to change your habits. Five years of updates have made Windows XP as secure as it can be, but still inferior in this parameter to Vista, Seven, Linux, and Mac OS X. Small resource requirements make this system the most suitable for computer games, while DirectX 10 will not take over the world. It is not demanding and satisfies all the basic needs of the user, but Microsoft is gradually pushing it out of the market, making room for its later products.

2. Microsoft Windows Vista

You will have to get Windows Vista if you buy new computer. Windows Vista's interface is more lively than that of XP, which will allow you to communicate more comfortably with the system during daily routines. Windows Vista includes some useful new tools and is safer for networking. However, it's not worth the price of a software upgrade and the loss in performance.

Windows Vista, frankly speaking, was not a success, now it is even considered an “inferior” operating system, but a kind of by-product, the transition from XP to Seven.

3. Windows Seven

For a moment Windows release 7, the most popular operating system was Windows XP. However, more than eight years have passed since its release, and during this time many new devices and technologies have appeared that require operating system support. After the advent of Windows Seven and updating equipment users, this system became quite good replacement for Windows XP, jumping over Windows Vista. Windows Seven is very successful product, which will appeal to many users, but it is demanding system resources your computer.

4. Linux

If you are tired of worrying about the safety of your data on your computer and dealing with countless malware, you can easily try Linux. Suddenly he will satisfy your requests. Just find your boot disk. The richest customization options make Linux distributions ideal option for users... with knowledge of Linux (programmers). For ordinary users who just want to work at the computer, the system is still not friendly enough.

5. Apple Mac OS X

Mac OS can be called the best operating system, but it has one huge drawback - to become its proud owner, you will have to buy a laptop Apple, and this is not a cheap pleasure. If Apple computers fits your budget, then Macintosh is a great choice. You will receive powerful tool with the most functional and user-friendly OS to date

Thus, today, the most the best option The operating system remains Windows XP.

References.

1. Computer science. Basic course / and others - St. Petersburg: Peter Publishing House, 2000.

2. Borisov of information science and computer technology./ – Rostov n/d: Phoenix, 2006

3. Computer Science: “Encyclopedic Dictionary for Beginners” / Comp. . – M.: Pedagogy-Press, 1994

4. http://aleksandrservis. *****/

Concept of functions and operating system

A modern computer system consists of one or more processors, RAM, disks, keyboard, monitor, printers, network interface and other devices, that is, it is complex integrated system. Writing programs that monitor all components, use them correctly, and still perform optimally is an extremely difficult task. For this reason, computers are equipped with a special layer of software called an operating system.

An operating system is a set of programs that manages the resources of a computer system, organizes computing processes in a broad sense and ensures interaction between users, programmers, application programs, system applications and computer hardware.

The operating environment is software environment An operating system that defines an application programming interface (API) as a set of system functions and services (system calls) provided to application programs. The operating environment may include multiple application programming interfaces

The operating system shell is, in general, a part of the operating system that defines the user interface, its implementation, command and service capabilities for managing application programs and the computer.

The development of operating systems is directly related to the development of computer technology. With the increase in the productivity of computer systems, the range of problems solved by computer systems gradually changed, expanded and became qualitatively more complex. The requirements for operating systems have changed accordingly. At the moment, it is possible to formulate a number of tasks for which the OS should be designed. These tasks can be divided into four main components:

• 1. Organization user-friendly interface between applications and users, on the one hand, and computer hardware, on the other hand. This may include:
  • · Program development. The OS provides various development tools (from API libraries to an editor)
  • · Execution of programs. The OS takes on all the tasks of loading the program into memory, providing programs with a uniform input-output interface for various devices, preparing resources, etc.
  • · Access to I/O devices. To control any device you need to know technical parameters and a device-specific set of commands. The operating system hides the complexity of interaction with devices and provides the user with a convenient universal user interface for all devices, and the programmer with a convenient software interface using simple read and write commands.
  • · Controlled access to files. Access to files is controlled by the OS depending on the type and structure of the file and the described rights of the subject wishing to access the file. In addition, conflict situations that arise in case of simultaneous access are controlled and resolved.
  • · System access. The OS controls access to the shared and public computing system as a whole, as well as to individual system resources, protects against unauthorized use and resolves conflict situations.
  • · Error detection and handling. The OS has its own means of monitoring errors that occur in executable programs and hardware, and also has the ability to independently process these errors if specific processing of the error that occurs is not provided for by the programmers in the corresponding program or hardware driver.
  • · Accounting for resource use. The OS often has built-in means of accounting for consumption and access to resources; an example is consumption counters network traffic in Linux OS and a system for auditing actions with files in the OS Windows versions 2000 and older.
• 2. Organizing the efficient use of computer resources depending on some efficiency criterion chosen by the OS developers. The criteria are selected by developers depending on the purpose of the OS. For example, for a system that controls a certain technical process (conveyor assembly, helicopter flight), the efficiency criterion will be the minimum reaction time to emerging external events, and for desktop computer-- Mandatory correct processing of all user actions (reactions to keystrokes, the ability to cancel a task, data safety), even if some programs are unstable. Resource management includes solving a number of common tasks, regardless of the resource type:
  • · Planning (allocation) - determining which process, when and in what quantity (if the resource can be allocated in parts) this resource should be allocated.
  • · Resource status tracking
  • · Accounting for resource use
  • · Resolving conflicts that arise when processes request resources
• 3. Facilitation of the processes of operating hardware and software computing system. This may include utilities, providing backup, data archiving, checking, cleaning, defragmenting disk devices, diagnostic programs, data recovery tools, etc.
• 4. Opportunity for development. Many modern operating systems are designed in such a way that they allow the efficient development, testing and implementation of new system functions without interrupting the functioning of the system.

Modern operating systems include hundreds and even thousands of modules aimed at solving various problems. Often these modules are grouped into subsystems according to their purpose. Each of these subsystems includes a set of modules and functions for solving a certain class of problem. These tasks can be divided into seven large classes. operating system table

• 1. Process management. The process management subsystem distributes the main resource of the computing system - processor time - among executing processes. In parallel, a number of general tasks are solved for the distribution of other resources and management of interprocessor interactions, for example: synchronizing processes and preventing the effect of races.
• 2. Memory management. The memory management subsystem distributes the available space physical memory between all processes existing at a given time, loads programs into memory, configures address-sensitive parts of the process code to the physical addresses of the allocated area, and also protects the memory areas of each process from the influence of other processes. One of the most convenient ways The memory management mechanism currently used is the virtual memory mechanism. This mechanism allows the programmer to work with memory as a potentially infinite resource (limited only by the addressing capabilities of a specific processor architecture). Moreover, regardless of the actual (possibly complex) memory allocation, this mechanism provides the program and the programmer with memory as a uniform sequence of cells, numbered starting from zero.
• 3. File management. The OS file subsystem virtualizes a set of data stored on external storage. For user convenience, files can be combined into groups - directories, in turn, directories and files can also be grouped into directories, forming a tree structure. Many implementations of file systems allow you to implement not only a tree structure for organizing information, but more complex structures when the same file or directory is displayed simultaneously in different parts of the structure (for example, in different directories). This organization of files is called a network, and the corresponding mathematical structure is called a network and is a special case of a more complex mathematical object - a graph. Virtualization of information in the form of files has proven to be so convenient that some operating systems have generalized this approach to other tasks of representing computer system resources. For example, file systems of the *nix family (Linux, Unix, Free BSD and others) display in file system a special directory /dev/, each file of which is actually an interface of a device, and for each device connected to the system, a special file. Thus, interactions with devices are reduced to write and read operations performed on such special files.
• 4. Management external devices. External device control functions form the input/output subsystem. The main difficulty in building this subsystem is that it must work with any connected device. Initially, the OS cannot “know” how to control all possible devices. For everyone specific device the manufacturer writes a special program that is built into the OS I/O subsystem and provides control of this device. Such a program is called a driver. Those. The I/O subsystem must be designed to allow the embedding of modules (drivers) written by third-party programmers (for example, hardware manufacturers), while the interactions between the I/O subsystem and other parts of the OS must remain correct.
• 5. Security and administration. The corresponding subsystem ensures data safety, access control, fault tolerance, control and error handling of processes and equipment. This subsystem influences the operation of other subsystems. One of its most important tasks is to determine the rights of the subject gaining access to the computer system. For this purpose, a logical login procedure is used, during which the user’s identity is “established” (the entered name and password are checked for compliance with the stored ones). This procedure is called authentication.

Authentication - confirmation of authenticity - a procedure for checking the correspondence of the subject and the one for whom he is trying to impersonate, using some unique information, in the simplest case - using a name and password.

When accessing a specific resource of a computer system, the security and administration subsystem performs another, no less important procedure - authorization. Authorization is the process, as well as the result of the process, of checking the necessary parameters and granting certain powers (access rights) to a person or group of persons to perform certain actions in systems with limited access.

In addition, many modern operating systems provide the ability to log (audit) user actions, on which the security of the system depends.

Also, the security and administration subsystem ensures fault tolerance of the computing system using both software and hardware.

• 6. Application programming interface. The development of modules of this subsystem occurs especially rapidly in lately. It was originally intended that the Application Programming Interface (API) subsystem would provide application programs with a set of functions that would simplify the writing of applications. For example, functions responsible for the graphical interface (rendering application windows, scaling them, moving them on the screen, etc.). Applications make calls to API functions using system calls, which are similar in logic to subroutine calls. Thus, these functions are not described in application programs, but are successfully used, which reduces the amount of code and time for writing programs, and also increases reliability. As a result of various libraries, such “convenient” functions became more and more numerous, the libraries themselves expanded, covering entire subject areas. Over time, the concept of an application programming interface has evolved into the concept of software application environments, which will be discussed later.
• 7. User interface. The user interface subsystem ensures convenient interaction between the user (programmer, administrator) and computer system, provides a convenient and intuitive interface for humans, ensures interactivity of work at the terminal (alphanumeric or graphic). When working with an alphanumeric terminal, the user interacts with the OS using commands typed in command line. If the OS supports a graphical interface, then interaction is carried out through a set. In addition, there are systems with voice user interface, but they are less common due to the complexity of the task of recognizing the voice of a random person. Such systems, as a rule, either recognize a very limited set of voice commands of an arbitrary person; or they recognize a fairly large set of commands, but are “trained” to the voice of one specific person. In the second case, the “training” process takes a lot of time.

Table 1. Data on the movement of goods for the month within the enterprise.

Table 1.1 Sorted data on the movement of goods for the month across the enterprise.

Table 2. Turnover sheet of goods movement for the month.

Table 2.1 Name of the product that has the lowest price.

Table 2.2 Name of goods that remained at the end of the month in quantities from 10 to 20 inclusive.

Table 2.3 Records of goods that were received more than 10 per month.

Table 3. Final data for each workshop and general results for the enterprise.

Bar chart of goods balances at the beginning and end of the month for one workshop.

A pie chart of total balances for the month for all departments of the enterprise.

List of used literature

• 1. Guidelines for completing tests in computer science for correspondence students / comp. N.D. Belova, N.I. Shchadrina. - Khabarovsk, 2010.
• 2. Selection instructions tests. Khabarovsk, 2011.
• 3. Computer science. Textbook for universities / Ed. N.V. Makarova. - M., 2001 Stepanov A.N. Informatics. Textbook for universities. St. Petersburg: Peter, 2008.
• 4. Bezruchko V.T. Workshop on the course “Informatics”. Working in Windows, Word, Excel: textbook. Manual for universities / V.T. Handless. - M.: Finance and Statistics, 2002.

The debate about which of these operating systems is better will probably never end. The most common and popular operating systems are Windows, Linux and Mac OS. Let's try to compare them.

Let's start with the fact that Linux belongs to the family of open and free systems. What does it mean? You can install the OS on your PC or laptop completely free of charge, and most importantly, legally. In turn, Mac OS and Windows belong to a closed (proprietary) family of operating systems. Copies of these must be purchased for installation. Pirated versions are widespread.

Now briefly about each of these operating systems:

Windows.Until recently, the most common operating system. According to statistics, it is installed on 85% of devices: tablets, laptops, computers. Used both at home and in businesses. With distribution mobile devices– smartphones, Linux began to push Windows. After all, it became the basis for Android.
The most important advantages are excellent compatibilityb and prevalence.

Linuxfrom the operating room family Unix systems. However, there are various distributions that have a kernel depending on the version, and are tailored for specific purposes. They are suitable for working on desktops for housewives, and for powerful cluster server systems.More than 80% of servers on the Internet are based on one of Linux distributions, FreeBSD or other Unix-like system. We talked about the basis for Android above.

The advantage is that shortcomings and inaccuracies can be quickly corrected thanks to the open source code.

Mac OS.The system that was developed by Apple. This is related software for devices produced by this corporation. Based on FreeBSD source code closed. Currently it occupies less than 20% of the market and is considered the second most popular.

Advantages: stability and performance.

Let's compare the OS in several ways.

System requirements.Of course, much less attention is now paid to this parameter than some 7–8 years ago. However, the number of applications that require significant resources to operate is increasing. This means that free space on your PC or other device will not be superfluous.

Windows.For stable operation of the latest version of the system, you will need a processor with two cores, 1 GB of RAM (and if you use a 64-bit distribution, even more), and not the worst video card.

Linux.Here the situation is simpler. All you need is a single-core processor, 256 MB of RAM (be prepared to buy an additional one right away) and absolutely any video card. Naturally, this will not be enough for applications to run quickly and surf the Internet easily. But minimum requirements exactly like that. Note that a plus will be the Zram kernel module, which allows you to compress data using zip before saving it to RAM.

Mac OS.Since the system is closed, it is impossible to draw an unambiguous conclusion. Theoretically, this OS can be launched with 512 MB of RAM, a single-core processor with a frequency of 1 GHz and 9 GB of free memory on the hard drive.

Security/virus protection.Most users store personal information, photos on their computers, make money transfers, communicate, etc. All this information requires protection. How stable are the operating systems chosen for comparison:

Windows.It is believed that this OS is the most vulnerable. This can be explained very simply: over latest versions less qualified employees work. This is confirmed by numerous errors in the code. If you remember Windows NT and Windows XP, the development process was well organized, hence the stability. That is why hackers come up with more and more new viruses under this shell. Also, Microsoft specialists fix very few vulnerabilities, and if they do, it takes a month or more.

Linux.If you look at Linux, “holes” are patched in a matter of hours. All products in the Unix family have very few flaws. It is possible to encrypt data, but doing this will require certain skills. As for pop-up blockers, you can forget about them.

Mac OS.The most secure OS, for hacking it there is even a good reward on some hacker sites. Helps maintain system stability by encrypting data and distributing it into personal and system ones. In addition, the new Mac OS is rewritten from scratch and is not compatible with previous versions. This means that finding ways to hack has become even more difficult.

The process of installing and configuring the OS.Here those being compared manifest themselves in different ways: someone« friendly» , and someone will cause a lot of trouble.

Windows.As practice shows, even a novice computer user can install it. The course of the entire operation is clear on an intuitive level. The downside is that you will have to look for some programs for the system to fully operate.

Linux.The installation process differs little from that described above, and sometimes it will be even easier to install the software. This applies specifically to the desktop version. If you need greater system customization and disk savings, then for installation you need to have at least a general understanding of the system packages and their interaction.

Mac OS.The installation process can be compared to a similar operation in Windows. To configure the system, ready-made System programs Preferences

Stability.Let's look at the differences in the work process.

Windows.Yes, outdated versions Indeed, they often failed. This is not the case with modern versions of the OS. Blue screens Deaths are now extremely rare.

Linux.Perhaps the most stable system of all three.

Mac OS.Crashes happen with about the same frequency as Windows. This most often occurs due to the use of programs that are incompatible with Apple standards.

Software support.Now let’s compare how they “treat” third party software operating systems presented.

Windows.Since this OS is the most common, software is most often written specifically for it. You can find a lot of paid and free software.

Linux.Every year a huge number of programs compatible with this system appear, and almost all of them are free. In addition, this OS has Wine and Mono emulators, which allow you to run most Windows applications directly from Linux.

Mac OS.There are a sufficient number of programs. The downside is that they can only be installed from the AppStore.

Ease of use.All developers strive to make their products as simple and accessible as possible to use, but not everyone succeeds.

Windows.No questions asked here.The interface is clear (except for Windows 8). Working on a computer is not difficult.

Linux.Each distribution is developed by a group of like-minded people from different countries, and not by individuals or companies. Anyone can choose a distribution based on the recommendations of other users, taking into account their knowledge and tastes.

Mac OS.Also comfortable and simple system, every little detail is taken into account. Working with it will be clear even to the uninitiated.

Instead of a conclusion.I would like to note that the choice should be based on requests. Decide what you need. Windows is a simple and intuitive system that is ideal for a novice user. Mac OS is perfectly optimized, pleasant to use, and productive. Linux is actively developing, it is already used by “armed” people and specialized specialists, and is also increasingly being installed on home computers. Take what suits you. Pushwe recommend going throughcourseat our Academy.