There are several types of operating systems: DOS, Windows, UNIX, Macintosh OS, Linux. Other modern operating systems, such as Linux, UNIX, OS/2, have their own advantages and disadvantages. Linux provides more advanced security than Windows and has a more sophisticated interface; UNIX is used where high system reliability is required. The big disadvantage of OS/2 and UNIX is the rather meager choice software, and here Windows wins over other operating systems.
The most common is the operating room Windows system. There are several versions of Windows: Windows-3.1, Windows-95, Windows-98, Windows-2000, Windows NT. All of them are close to each other in content. Therefore, we will consider such operating systems as DOS and Windows-95.
MS-DOS is one of the first operating systems and one of the most famous. The popularity of this operating system peaked in the 90s; now this operating system is rarely used. Most popular in the world this moment Microsoft operating systems are used. Their share is about 90% among all operating systems. The most stable systems of this company are based on NT technology.
Operating system DOS
The DOS operating system consists of the following parts:
1) Basic input/output system (BIOS), located in the read-only memory (read-only memory, ROM) of the computer. This part of the operating system is "built into" the computer. Its purpose is to perform the most simple and universal operating system services related to I/O. The basic I/O system also contains a computer performance test that checks the operation of the computer's memory and devices when the computer's power is turned on. In addition, the basic input/output system contains a program that calls the operating system loader.
2) The operating system loader is a very short program located in the first sector of every DOS floppy disk. The function of this program is to read two more operating system modules into memory, which complete the DOS boot process.
3) The DOS command processor processes commands entered by the user. The command processor is in a disk file! COMMAND.COM on the disk from which the operating system boots. Some user commands, such as Type, Dir or Sop) command processor does it himself. Such commands are called internal. To execute other (external) user commands, the command processor searches the disks for a program with the appropriate name and, if it finds it, loads it into memory and transfers control to it. At the end of the program, the command processor deletes the program from memory and displays a message indicating that it is ready to execute commands (DOS prompt).
External commands DOS are programs that come with the operating system as separate files. These programs perform maintenance actions, such as formatting floppy disks, checking disks, etc.
Device drivers are special programs that complement the DOS input/output system and provide support for new or non-standard use of existing devices. For example, with the help of drivers it is possible to work with an “electronic disk”, i.e. a piece of computer memory that can be manipulated in the same way as a disk. Drivers are loaded into the computer's memory when the operating system boots; their names are indicated in a special CONFIG file.SYS. This design makes it easy to add new devices and allows you to do this without affecting system files DOS.
Window-95 evolved from a graphical add-on for DOS into a full-fledged operating system. At least that's what its developers said. In reality, everything was more complicated: Windows 95 still used good old DOS as its basis. Slightly modernized, of course, and not declared as a separate product. However, most consumers were happy with this option. After all, they still had the opportunity to work in the usual DOS mode without loading the Windows graphical shell, and, therefore, not to part with the usual DOS programs.
Also, the Window-95 operating system became 32-bit. All previous versions of DOS and Windows were 16-bit and, therefore, could not fully use the capabilities of even the 386 family of processors, much less the new ones Pentium processors. Of course, this advantage also contained some inconveniences. Especially for Windows, users had to replace all their Windows programs with new 32-bit versions. However, in practice the transition turned out to be relatively easy. Already throughout the year, new versions of all popular software products have been released. But the old 16-bit versions could work with the new OS without any problems.
Operating system, OS (English operating system) - a basic set of computer programs that provides a user interface, control of computer hardware, work with files, input and output of data, as well as execution of application programs and utilities.
The operating system is the piece of software most closely related to technical means computer (hardware).
Main OS functions:
Computer resource management: CPU time, distribution internal memory, files, external devices;
Organizing a dialogue with the user;
Booting the computer;
Launching programs for execution;
Equipment testing.
Operating system MS-DOS
The MS-DOS operating system consists of many different files. They include the actual operating system files IO.SYS, MSDOS.SYS and the command processor COMMAND.COM. In addition to these three files, which represent a working MS-DOS kernel, the operating system distribution includes files of so-called external commands, for example FORMAT, FDISK, SYS, drivers for various devices and some other files.
The IO.SYS file contains an extension to the basic input/output system and is used by the operating system to interact with the computer hardware and BIOS.
The MSDOS.SYS file is in a sense a set of interrupt handling programs, in particular the INT 21H interrupt.
The COMMAND.COM command processor is designed to organize a dialogue with the computer user. It analyzes commands entered by the user and organizes their execution. The so-called internal commands - DIR, COPY, etc. are processed by the command processor.
The remaining operating system commands are called external commands. External commands are so named because they are located in separate files. Operating system external command files contain utility programs for performing a variety of operations, such as formatting disks, sorting files, and printing texts.
Drivers (usually files with the extension SYS or EXE) are programs that support various hardware. The use of drivers easily solves the problems of using new equipment - just connect the appropriate driver to the operating system.
Application programs interact with the device through the driver, so they will not change when the hardware changes. For example, new disk device may have a different number of tracks and sectors, different control commands. All this is taken into account by the driver, and the application program will work with the new disk as before, using DOS interrupts.
The basic input/output system (BIOS) is located in the computer's read-only memory (ROM) and is “built-in” into the computer (the information in the ROM is retained even after the computer is turned off, i.e. it has the property of being non-volatile). Its purpose is to perform the most simple and universal operating system services related to I/O. It also contains a computer functioning test, which checks the operation of the computer's memory and external devices when the power supply is turned on, and a program for calling the operating system loader.
The operating system loader is a very short program located in the first sector of each operating system floppy disk; the function of this program is to read the remaining operating system modules into memory, which completes the boot process. On a hard drive, the operating system boot loader consists of two parts. This is due to the fact that HDD can be divided into several partitions (logical drives). The first part of the bootloader is in the first sector hard drive, it selects which partition of the hard drive to continue booting from. The second part of the bootloader is located in the first sector of this section; it reads DOS modules into memory and transfers control to them.
OS modules (io.sys and msdos.sys) are loaded into memory by the operating system loader and remain in the computer's memory permanently. (The io.sys file is an add-on to the BIOS, and the msdos.sys file implements basic high-level DOS services.)
The DOS command processor (command.corn) processes commands entered by the user. The command processor is located on the disk from which the operating system boots. Some user commands (for example, type, dir or copy) are executed by the shell itself. Such commands are called internal. To execute other (external) user commands, the command processor searches the disks for a program with the appropriate name and, if it finds it, loads it into memory and transfers control to it. At the end of the program, the command processor deletes the program from memory and displays a message indicating that it is ready to execute commands—a DOS prompt.
External DOS commands are programs that come with the operating system as separate files. They perform maintenance activities, such as formatting floppy disks, checking disks, etc.
Device drivers are special programs that complement the DOS input/output system and provide support for new or non-standard use of existing devices. Drivers are loaded into the computer's memory when the operating system boots; their names are indicated in a special file (config.sys). This design makes it easy to add new devices and allows you to do so without affecting DOS system files.
When you turn on the computer's power supply (or when you press the Reset key on the computer case, or when you simultaneously press the Ctrl, Alt and De1 keys on the keyboard), hardware check programs located in the computer's permanent memory begin to run. If they find an error, they display the error code on the screen.
After testing is completed, the program bootstrap tries to read the operating system loader program from a floppy disk installed on the drive (a:). If there is no floppy disk on the drive, the OS will be loaded from the hard drive.
After the OS loader program is read from the disk from which the OS is loaded, this program reads the operating system modules (io.sys and msdos.sys) into memory and transfers control to them.
Next, the system configuration file (config.sys) is read from the same disk and, in accordance with the instructions contained in this file, device drivers are loaded and operating system parameters are set. If such a file is missing, the parameters are set by default.
After this, the command processor (command.com) is read from the disk from which the OS is loaded and control is transferred to it. The command processor executes batch file(autoexec.bat), if this file is present in the root directory of the disk from which the OS is loaded. This file specifies the commands and programs that are executed each time the computer starts. If such a file is not found, then DOS asks the user for the current date and time.
After executing this file, the operating system boot process ends. DOS issues a prompt indicating that it is ready to receive commands.
C:\USERS\ is an example of a DOS prompt.
The active line with the DOS prompt is called the command line. In it, the user types commands to execute.
operating system Windows XP
Main Windows elements XP are:
System desktop.
Icon – small graphic image, which should let the user understand what it is for this program or folder (file).
Pictograms are very small and primitive icons, usually containing some kind of geometric object. Icons usually indicate certain actions, such as playing music or a movie, stopping, pausing, etc.
Folders in Windows XP perform essentially the same function as folders in the office: they store documents (files) and other folders:
There are regular folders that can be called whatever you want, and there are also special folders whose names are reserved as: my documents, my drawings, my music.
You can perform various actions with folders: rename, move (to another volume or another folder), delete or copy. When copying a folder, all its contents are duplicated as well.
folders can be nested inside each other, thus creating developed tree structures.
A shortcut is an icon with a special icon that is a link to some element (file, program, folder). Using shortcuts, you can make it easier to access an item, for example, by placing a shortcut to the item on your desktop.
A window is the main element of the Windows XP operating system. Each running program turns into a window with which you can perform various actions: close, reduce or increase in size, minimize and maximize, minimize. Closing the window is the end of the program. Minimizing a window is a completely different process: the program continues to work in background, and the window turns into a button on the taskbar.
Basic Windows tools XP:
“Start” button – using this button you can start any program, even one whose icon is not present on the desktop.
The "My Documents" folder is for documents. More precisely, for files that are created using certain programs. It is also recommended to place any sent or sent documents in it. If all documents are stored in this folder, it will facilitate their archiving and storage.
The “My Pictures” and “My Music” folders are located inside the “My Documents” folder.
Recent Documents is not a folder, but simply a list of files you've recently worked with.
The Start button is convenient to use to access the Control Panel folder. Using this button, you can configure many operating system settings, as well as help and search engines.
“My Computer” is a folder that displays your entire computer: hard drive, removable drive and other devices (floppy drives, CD-ROMs, external drives).
The “Shared Documents” folder is used to place files there that will be available to all users of this computer.
“Taskbar” – it contains buttons for currently running programs. The color of the button for the currently active task differs from the color of the buttons for inactive tasks. The taskbar contains more than just window buttons. It may also contain toolbars.
“Toolbar” are special areas that are located on the taskbar, in which icons of certain programs are located.
The notification area is a special section on the taskbar where icons of constantly running programs are located. Windows XP allows you to independently configure which icons in the notification area are always shown and which ones are hidden.
Windows XP is a self-sufficient system. It contains a whole set of application programs that allow you to listen to music, burn CDs, work with files, create various documents, process photographs, draw pictures, use all the capabilities of the Internet - browse web pages, receive and send e-mail, communicate via the Internet -messengers, play computer games.
IV. Describe the main STANDARD applications Windows OS and principles of working with them
Standard programs are included in the Windows operating system itself (text editor WordPad, graphics editor Paint, virtual calculator and much more).
Windows Explorer is a special program designed to make it easier to work with folders and files.
Text editor WORD PAD is a simple, but nevertheless quite effective text editor.
Calculator – a regular calculator, only in the form of a program. It has two options: a regular and an engineering calculator.
Graphic PAINT editor– a simple graphic editor that allows you to simple tasks users shooting with a digital camera, drawing pictures.
Windows Media Player is a powerful multifunctional program that allows you to watch movies in various formats, listen to music, broadcast radio channels, convert music tracks in various formats, burn CDs and create multimedia libraries.
Archives are so-called zip folders. This is a very useful and popular way of storing information.
Additional programs- these are those programs that are purchased and installed independently, in addition to the standard Windows package.
Depending on the implemented architectural solutions, the characteristics of operating systems are:
· Portability - refers to the ability to work on CISC AND RISC processors.
· Multitasking – using one processor to run multiple applications.
· Multiprocessing - involves the presence of several processors that can simultaneously execute many threads, one for each processor present in the computer.
· Scalability – the ability to automatically take advantage of added processors. So, to speed up the application, the operating system can automatically connect additional identical processors.
· Client-server architecture – involves connecting a single-user workstation general purpose (client) to a multi-user general purpose server to distribute the data processing load between them. The object that sends the message is the client, and the object that receives the message and responds to it is the server.
· Extensibility – ensured by an open modular architecture that allows you to add new modules to all levels of the operating system.
· Reliability and fault tolerance - characterize the ability to protect the operating system and applications from destruction.
· Compatibility means continued support for applications developed for MSDOS operating systems such as Windows, OS/2.
· Multi-level security system to protect information and applications from destruction, unauthorized access, and unskilled user actions.
Classification of operating systems
OS can be classified according to various criteria:
· Based on the number of tasks being solved on a computer in parallel OS is divided:
- single-tasking (for example, MS DOS);
- multitasking (OS/2, UNIX, Windows, Linux).
Multitasking operating systems provide simultaneous solving of several tasks and manage the distribution of shared resources (processor, RAM, files and external devices).
· By number of simultaneously working users :
- single-user (for example, MS DOS, Windows 3.x);
- multi-user (network Unix, Linux, Windows 2000).
The main difference between multi-user systems and single-user systems is the ability to work on a computer network.
· By user interface:
- command interface (for example, MS DOS);
- graphical interface (for example, Windows).
· According to the number of bits of the computer address bus, for which the OS is oriented,
- to 16-bit (MS DOS);
- 32-bit (Windows 2000) and
- 64-bit (Windows 2003).
In the sector software and operating systems, the leading position is occupied by IBM, Microsoft, UNISYS, Novell.
Operating system MS DOS(Microsoft) appeared in 1981. Today this operating system is installed on the vast majority of personal computers. Since 1996, MS DOS has been distributed as Windows 95 - a 32-bit multitasking and multi-threaded operating system with a graphical interface and advanced network capabilities.
Most traditional comparison OS is carried out according to the following characteristics of the information processing process:
· memory management (maximum amount of addressable space, types of memory, technical indicators of memory use);
· functionality of auxiliary programs (utilities) as part of the operating system;
· presence of disk compression;
· possibility of archiving files;
· support for multitasking mode;
· network software support;
· availability of high-quality documentation;
· conditions and complexity of the installation process.
Network operating systems- a set of programs that provide processing, transmission and storage of data on the network. Network OS provides users with different kinds network services (file management, e-mail, network management process, etc.), supports work in subscriber systems. Network operating systems use architecture client-server or peer-to-peer architecture. At first, network operating systems supported only local area networks (LANs), but now these operating systems extend to associations local networks.
operating system(OS) is a set of programs that provides management of computer resources and processes that use these resources during calculations. Process is a sequence of actions prescribed by the program. Resource is any logical or hardware component of a computer. The main resources are CPU time and RAM. Resources may belong to one or more external computers that the operating system accesses using a computer network.
Resource management consists of two functions: simplifying access to a resource and distributing resources between processes competing for them. To solve the first problem, operating systems support custom And software interface s . To solve the second, operating systems use various virtual memory and processor management algorithms.
Operating systems are characterized by the following main features:
· number of users simultaneously served by the system (single-user and multi-user);
· number of simultaneously running processes (single-task and multi-task);
· the type of computing system used (uniprocessor, multiprocessor, network, distributed).
Example. The Windows98 operating system is multitasking, Linux is multi-user, MS-DOS is single-tasking and therefore single-user. Windows NT and Linux operating systems can support multiprocessor computers. The Novell NetWare operating system is a network operating system; Windows NT and Linux also have built-in network tools.
User and software interfaces. To simplify access to computer resources, operating systems support user and program interfaces. A user interface is a set of commands and services that make it easier for the user to work with a computer. A software interface is a set of procedures that make it easier for a programmer to control a computer.
Rice. 1. Operating system interfaces
Example. Windows OS provides the user with a graphical interface, which is (from the user's point of view) a set of rules for visual control of the computer. In addition to the main graphical interface, the user is also provided with a command interface, that is, a set of commands of a certain format. To do this, there is a “Run” item in the system menu. A set of system functions in Windows is called API (Application Programming Interface). This set contains more than a thousand procedures for solving various system problems. The Linux operating system also has two options for controlling a computer, but, as a rule, preference is given to commands.
Processor time and memory organization. To organize multitasking mode, the OS must somehow distribute the processor's operating time between simultaneously running programs. Typically, the so-called preemptive multitasking mode is used. In preemptive mode, each program runs continuously for a strictly defined period of time (time slice), after which the processor switches to another program. Since the time quantum is very small, with sufficient processor performance, the illusion of simultaneous operation of all programs is created.
One of the main tasks of the operating system is memory management. When there is not enough main memory, all data that is not currently in use is written to a special page file. The memory represented by the page file is called external page memory. The combination of main and external page memory is called virtual memory. However, to the programmer, virtual memory appears as a single unit, that is, it is treated as an unordered collection of bytes. In this case, linear memory addressing is said to be used.
Example. Windows and Linux operating systems use linear addressing of virtual memory. The MS-DOS operating system used non-linear addressing of main memory. The main memory had a complex structure that had to be taken into account when programming. Page files were not supported by MS-DOS.
Operating system structure. Modern operating systems, as a rule, have a multi-level structure. Works directly with the equipment core operating system. A kernel is a program or a collection of related programs that use the hardware features of a computer. Thus, the kernel is a machine-dependent part of the operating system. The kernel defines a programming interface. On the second level there are standard programs operating system and shell, which operate the kernel and provide the user interface. They try to make second-level programs machine-independent. Ideally, replacing a kernel is equivalent to replacing the version of the operating system.
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Rice. 2. Operating room levels Linux systems
File system. Any data is stored in external memory Computers in the form of files. Files need to be managed: created, deleted, copied, modified, etc. The OS provides such tools to the user in the form of user and program interfaces. The way files are organized and managed is called a file system. The file system determines, for example, what characters can be used for a file name, what the maximum file size is, what the root directory name is, etc. The way files are organized affects the speed of access to the required file, on the security of file storage, etc.
The same OS can work simultaneously with several file systems. As a rule, file system functions are implemented by means of the operating system kernel.
Example. Several types of file systems are used for PCs:
FAT16 – used in Windows95, OS\2, MS-DOS;
FAT32 and VFAT – used in Windows95 OS;
NTFS – used in Windows NT OS;
HPFS – used in OS\2;
Linux Native, Linux Swap - used in Linux OS.
The FAT file system has the simplest structure. The name of the root directory always looks like: A:\, B:\, C:\, etc. The file name consists of three parts: path, actual name, extension. Path is the name of the directory where the file is located. The extension indicates the file type. For example, the full file name is C:\Windows\System\gdi.exe, the path is C:\Windows\System\, the extension is exe, the actual name is gdi. According to FAT rules, the file name itself can contain from 1 to 8 characters, and the name extension, separated from the name by a dot, can contain up to 3. When naming files, uppercase and lowercase letters do not differentiate. The full file name includes the name logical device, where the file is located and the name of the directory in which the file is located. The system stores information about the file size and the date it was created.
In terms of data organization, VFAT resembles FAT. However, it allows you to use long file names: names up to 255 characters, full names up to 260. The system also allows you to store the date of last access to the file, which creates additional opportunities for fighting viruses.
The file system can be implemented as a driver with which all programs that read or write information to external devices communicate through the operating system. The file system may include security features for storing information. For example, the NTFS file system has tools for automatically correcting errors and replacing bad sectors. A special mechanism monitors and records all actions performed on magnetic disks, so in the event of a failure, the integrity of the information is restored automatically. In addition, the file system may have means of protecting information from unauthorized access.
Client-server model. An important feature of modern operating systems is that the interaction between the application program and the OS is based on the client-server model. All requests user program(client) to the OS are processed by a special program (server). This uses a mechanism similar to calling a remote procedure, which makes it easy to move from interaction between processes within one computer to a distributed system.
Plug and play technology. Plug and play technology (PnP technology) refers to the method of interaction between the OS and external devices. The operating system polls all peripheral devices and must receive a specific response from each device, from which it can be determined 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 should be spared the complex work of setting up an external device, which requires high qualifications.
Service systems– a software product that changes and complements the user and software interfaces of the OS. Service systems are differentiated into operating environments, shells, and utilities.
Operating environment– a system that changes and complements both the user and software interface. The operating environment creates for the user and application programs the illusion of working in a full-fledged OS. The emergence of an operating environment usually means that the operating system in use does not fully meet the requirements of practice.
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Rice. 3. Role of the operating environment
Data protection– this is a very big problem. Within the framework of the OS, information protection mainly means ensuring the integrity of information and protection from unauthorized access. Ensuring integrity rests primarily with file system, and protection against unauthorized access is on the core. A common mechanism for such protection is the use of passwords and privilege levels. For each user, the boundaries of access to files and the priority of his programs are determined. The system administrator has the highest priority.
Network tools and distributed systems. An integral part of modern operating systems are tools that allow you to communicate via a computer network with applications running on other computers. To do this, the OS solves mainly two problems: providing access to files on remote computers And the ability to run a program on a remote computer.
The first task is most naturally solved by using the so-called network file system, which organizes the user’s work with deleted files as if these files were on the user’s own magnetic disk.
The second problem is solved using the remote procedure call mechanism, which is implemented by the kernel and also hides the difference between local and remote programs from the user.
The availability of tools for managing the resources of remote computers is the basis for the creation of distributed computing systems. A distributed computing system is a collection of several connected computers that work independently, but perform a common task. Such a system can be considered as a multiprocessor.
Shell– a system that changes the user interface. The shell creates an interface for the user that is different from that of the operating system itself. The purpose of the shell is to simplify some commonly used operations with the operating system. However, the shell will not replace the OS, and therefore a professional user must also study the command interface of the OS itself.
Utilities have a highly specialized purpose and each perform its own function. Utilities are executed in the environment of the corresponding shells and provide users with additional services (mainly for maintaining disks and files). Most often this is:
Disk maintenance (formatting, ensuring the safety of information, the ability to restore it in case of failure, etc.);
Maintenance of files and directories (search, viewing, etc.);
Creating and updating archives;
Providing information about computer resources, disk space occupancy, distribution random access memory between programs;
Print text and other files to various modes and formats;
Protection against computer viruses.
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Rice. 4. The role of the OS shell
Instrumentation systems is a software product that provides information and software development. Instrumental systems include: programming systems, rapid application development systems and database management systems (DBMS).
Programming system is intended for developing application programs using some programming language. It includes:
· compiler and/or interpreter;
· link editor;
· development environment;
· library of standard routines;
· documentation.
A compiler is a program that converts a source program into an object module, that is, a file consisting of machine instructions. An interpreter is a program that directly executes the instructions of a programming language.
A link editor is a program that assembles multiple object files into a single executable file.
An integrated development environment is a set of programs that includes a text editor, software project file management tools, and a program debugger that automates the entire program development process.
A library of standard routines is a set of object modules organized into special files that are provided by the manufacturer of the programming system. Such libraries usually contain text input/output routines, standard mathematical functions, and file management programs. Object modules from the standard library are usually automatically linked by the linker to user-defined object modules.
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Rice. 5. Stages of program development
Rapid application development systems represent a development of conventional programming systems. In RAD systems, the programming process itself is largely automated. The programmer does not write the program text itself, but with the help of some visual manipulations indicates to the system what tasks should be performed by the program. After which the RAD system itself generates the program text.
Database Management System is a universal software tool designed to organize the storage and processing of logically interrelated data and provide quick access to it. One of important opportunities A computer is the storage and processing of large volumes of information, and on modern computers there is an accumulation of not only text and graphic documents (drawings, drawings, photographs, geographical maps), but also Web pages global network Internet, sound and video files. Creation of databases ensures data integration and the ability to centrally manage them. Databases collect information organized according to certain rules that provide general principles for describing, storing and manipulating data so that various users and programs can work with it.
DBMSs enable programmers and system analysts to quickly develop more advanced data processing software, and end users to directly manage data. The DBMS must provide the user with search, modification and storage of data, online access, protection of data integrity from hardware failures and software errors, differentiation of rights and protection from unauthorized access, support for collaboration of several users with data. There are generic database management systems used for various applications. When setting up universal DBMSs for specific applications, they must have the appropriate tools. The process of customizing a DBMS for a specific application area is called system generation. Universal DBMSs include, for example Microsoft systems Access, Microsoft Visual FoxPro, Borland dBase, Borland Paradox, Oracle.
Telecommunications data processing technologies. An important feature of many operating systems is the ability for them to interact with each other via a network, which allows computers to interact with each other as within local computer networks(LAN) and on the global Internet.
Modern operating systems, both newly created and updated versions existing ones, support a full set of protocols for working in local and global computer networks. At the moment, the global computer industry is developing very rapidly. System performance increases, and therefore the ability to process large volumes of data increases. Operating systems of the MS-DOS class can no longer cope with such a flow of data and cannot fully utilize resources modern computers. Therefore, it is not widely used anywhere else. Everyone is trying to switch to more advanced operating systems, such as Unix, Windows, Linux or Mac OS.
If we define the OS in the user's words, then operating system can be called the most important program, which is loaded first when the computer is turned on and thanks to which communication between the computer and a person becomes possible. The task of the OS is to ensure the convenience of working with a computer for a human user. The OS manages all devices connected to the computer, providing access to them to other programs. In addition, the OS is a kind of buffer-transmitter between computer hardware and other programs; it receives command signals sent by other programs and “translates” them into a language understandable to the machine.
It turns out that every OS consists of at least three required parts:
First - core , command interpreter , “translator” from software language to “hardware”, machine code language.
The second is specialized programs for controlling 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 by the operating system itself and by the programs included in it.
And finally, the third part is a convenient shell with which the user communicates - interface . 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 operating system; the kernel, the main part of the OS, is remembered only later. That's why an OS as unstable and unreliable from the point of view of the kernel as Windows 98/ME enjoyed such stunning success - thanks to its beautiful interface wrapper.
Today, a graphical interface is an invariable attribute of any operating system, be it Windows XP, Windows NT or Mac OS (an operating system for Apple computers Macintosh). The first generations of operating systems had a text interface rather than a graphical one, that is, commands were given to the computer not by clicking on an icon, but by entering commands from the keyboard. For example, today to run a text editing program Microsoft Word Just click on the icon of this program on the Windows Desktop. Previously, when working in the previous generation OS - DOS, it was necessary to enter a command like
C:\WORD\word.exe mybook.doc.
OS are classified by:
number of concurrent users: single-user (intended to serve one client) and multi-user (designed to work with a group of users simultaneously at different terminals). An example of the first is Windows 95/98, and the second is Windows NT. For home use you will need a single-user OS, but for a local office or enterprise network you need a multi-user OS;
number of processes simultaneously running under the control of the system: single-tasking , multitasking. Single-tasking operating systems (DOS) can perform no more than one task at a time, while multitasking operating systems can support the parallel execution of several programs that exist within the same computer system, dividing the computer's power between them. For example, a user can enter text into a Word document while listening to music from a favorite CD, while the computer copies a file from the Internet at the same time. In principle, the number of tasks that your OS can perform is not limited by anything other than processor power and RAM capacity;
number of supported processors: single-processor , multiprocessor (support the mode of distributing resources of several processors to solve a particular task);
operating system code bit depth:
Ø 16-bit (DOS, Windows 3.1),
Ø 32-bit (Windows 95 - Windows XP),
Ø 64-bit (Windows Vista);
The OS capacity cannot exceed the processor capacity;
interface type: team
(text) and object-oriented
(usually graphic);
· type of user access to the computer:
Ø with batch processing - from the programs to be executed, a package of tasks is formed, entered into the computer and executed in order of priority, with possible consideration of priority),
Ø time-sharing - simultaneous dialogue (interactive) mode of access to the computer of several users on different terminals is provided, to which machine resources are allocated in turn, which is coordinated by the OS in accordance with a given maintenance discipline),
Ø real time - provide a certain guaranteed response time of the machine to the user’s request with the user’s control of any events, processes or objects external to the computer. RV OS is mainly used in automation of such areas as oil and gas production and transportation, control technological processes in metallurgy and mechanical engineering, chemical process control, water supply, energy, robot control. Of these, QNX RT OS stands out for its full set tools that the user is accustomed to when working with UNIX operating systems.
· type of resource use: network, local . Network operating systems are designed to manage the resources of computers connected to a network for the purpose of sharing data, and provide powerful means of restricting access to data to ensure their integrity and safety, as well as many service capabilities for using network resources. In most cases, network operating systems are installed on one or more fairly powerful server computers dedicated solely to maintaining the network and shared resources. All other operating systems will be considered local and can be used on any personal computer connected to the network as a workstation or client.
Finally, another division - specialization , the purpose of a particular OS. After all, no matter what individual executives of a separate software corporation say, universal operating systems do not exist. One is more suitable for working on the network, the other will be chosen by programmers, and the third by home users. As practice shows, knowledge of one OS in our time is by no means enough. In your professional work, you will probably have to deal not only with Windows, but also with other operating systems - and you need to prepare for this in advance.
Machine-dependent OS properties are:
· interrupt handling;
· process planning;
· input/output control;
· real memory management;
· virtual memory management.
Machine-independent OS properties are:
· work with files;
· methods of scheduling user tasks;
· organization of parallel operation of programs;
· distribution of resources;
· protection.
The main criteria for the approach when choosing an operating system. There are a large number of OSes and the user must determine which OS is better than others (according to certain criteria). To choose one or another OS, you need to know:
· on what hardware platforms and at what speed the OS runs;
What peripheral hardware does the OS support?
· how fully the OS satisfies the user’s needs, i.e. what are the functions of the system;
· what is the way the OS interacts with the user, i.e. how visual, convenient, understandable and familiar the interface is to the user;
· are there informative tips, built-in reference books, etc.;
· what is the reliability of the system, i.e. its resistance to user errors, equipment failures, etc.;
What capabilities does the OS provide for organizing networks?
· does the OS provide compatibility with other operating systems;
What tools does the OS have for developing application programs?
Does the OS support various national languages?
· what known application software packages can be used when working with this system;
· how the OS protects information and the system itself.
Here I want to introduce the most common operating systems that we use in our daily work: Dos, Windows 3.+, Windows 95.
Disk Operating System (DOS)
The DOS operating system consists of the following parts:
Basic input/output system (BIOS), located in the computer's read-only memory (read-only memory, ROM). This part of the operating system is “built into” the computer. Its purpose is to perform the most simple and universal operating system services related to I/O. The basic I/O system also contains a computer performance test that checks the operation of the computer's memory and devices when the computer's power is turned on. In addition, the basic input/output system contains a program that calls the operating system loader.
The operating system loader is a very short program found in the first sector of every DOS floppy disk. The function of this program is to read two more operating system modules into memory, which complete the DOS boot process.
On a hard drive (hard drive), the operating system boot loader consists of two parts. This is due to the fact that the hard drive can be divided into several partitions (logical drives). The first part of the bootloader is in the first hard sector disk, it selects from which partition of the hard drive it should continue loading. The second part of the boot loader is located in the first sector of this partition; it reads modules into memory DOS and transfers control to them.
Disk files 10. SYS and MSDOS. SYS (they may be called differently, for example, IBM. COM and IBMDOS. COM for PC DO; URBIOS. SYS and DRDOS. SYS for DR DOS - the names change depending on the version of the operating system). They are loaded into memory by the operating system loader and remain in the computer's memory permanently. File I0. SYS is an addition to the basic ROM I/O system. MSDOS file. SYS implements basic high-level DOS services.
The DOS command processor processes commands entered by the user. The command processor is in a disk file! COMMAND. COM on the disk from which the operating system is loaded. Some user commands, such as Type, Dir or Cop), are executed by the command processor itself. Such commands are called internal. To execute other (external) user commands, the command processor searches the disks for a program with the appropriate name and, if it finds it, loads it into memory and transfers control to it. At the end of the program, the command processor deletes the program from memory and displays a message indicating that it is ready to execute commands (DOS prompt).
External DOS commands are programs that come with the operating system as separate files. These programs perform maintenance actions, such as formatting floppy disks, checking disks, etc.
Device drivers are special programs that complement the DOS input/output system and provide support for new or non-standard use of existing devices. For example, with the help of drivers it is possible to work with an “electronic disk”, i.e. a piece of computer memory that can be manipulated in the same way as a disk. Drivers are loaded into the computer's memory when the operating system boots, and their names are specified in a special CONFIG file. SYS. This scheme makes it easy to add new devices and allows you to do this without affecting the DOS system files.
DOS versions
The first version of the operating system for the IBM PC computer, MS DOS 1.0, was created by Microsoft in 1981. Later, as IBM PC computers improved, new versions of DOS were released, taking into account the new capabilities of computers and providing additional convenience to the user.
In 1987, Microsoft developed version 3.3 (3.30) of the MS DOS operating system. which became the de facto standard for the next 3-4 years. This version is very compact and has a sufficient range of capabilities, so that its operation on a “standard IBM PC AT” is still quite advisable. But for more powerful computers with several megabytes of RAM, it is advisable to use versions 5.0 or 6.0 of the MS DOS operating system. These versions have tools for efficient use of RAM above 640 KB, allow you to work with logical disks larger than 32 MB, transfer DOS and device drivers to extended memory, freeing up space in regular memory for application programs, etc. Version 6.0 MS DOS includes tools for compressing information on disks (DoubleSpace), programs for creating backup copies, antivirus program and other minor improvements. However, in this version, information compression programs did not always work correctly, which led to data loss for some users. To eliminate these problems and other errors, Microsoft released MS DOS 6.20. This version is more stable, reliable and faster than MS DOS 6.0 and includes a number of minor improvements. However, a court decision regarding violation of Stack Electronics patents in MS DOS forced Microsoft to first release MS DOS 6.21. in which the DoubleSpace dynamic disk compression program, which violated the patent, was seized, and then MS DOS 6.22 with a “tweaked” version of DoubleSpace that did not violate the patent. By in my opinion from of these versions the best is 6.20.
The Windows 3.1 operating shell is an add-on developed by Microsoft over the DOS operating system, providing a large number of features and convenience for users and programmers. The widespread use of Windows has made 661 the de facto standard for IBM PC-compatible computers: the vast majority of users of such computers work on Windows, so Lately Almost all new programs are developed specifically for their use in Windows environment. "Unlike shells like Norton Commander, Windows not only provides a convenient and visual interface for operations with files, disks, etc., but also provides new opportunities for those running in the environment Windows programs. Of course, to use these features, programs must be designed to meet Windows requirements. Such programs cannot be executed outside the Windows environment, so we will call them Windows programs or WincSows applications. However, Windows can also perform regular programs, designed for DOS, but such programs do not take advantage of any of the benefits of Windows and are slower than when called directly from DOS.
The Windows 3.1 shell includes many components and provides users of various qualifications with a comfortable working environment.
Version 3.0 of the Windows shell (and the subsequent 3.1) professes completely different principles in terms of the user interface with the computer. (These principles may be considered new, but machines Apple have been built on these principles for several years.) The main idea underlying the Windows shell is the naturalness of the presentation of information. Information should be presented in a form that ensures the most effective assimilation of this information by a person. Despite the simplicity (and even triviality) of this principle, its implementation in the interfaces of application programs of personal computers for various reasons left much to be desired. And its implementation within Windows 3.1 is also not without its drawbacks. But this shell represents a significant improvement over previous computer user interfaces. The most important distinctive features its are as follows: Windows is closed working environment. Almost any operation available at the operating system level can be performed without leaving Windows. Launching an application program, formatting floppy disks, printing texts - all this can be called from Windows and returned to Windows upon completion of the operation. DOS experience will come in handy here too; Many of the fundamental principles and concepts of the Windows environment are the same as those of the DOS environment. The basic concepts of the user interface in the Windows environment are the window and the icon. Everything that happens within the Windows shell is, in some sense, either an operation on an icon or an operation on a window (or in a window). The structure of windows and the arrangement of their controls are standardized in the Windows environment. Sets of operations and menu structure have been standardized for service programs. Operations performed using the mouse are standard for all service and application programs.
Windows is graphical shell. The user is not required to enter directives from the keyboard in the form of text strings. You just need to be careful look on the screen and select the required operation from the proposed set using the mouse. The mouse cursor follows position on the field of the required menu directive, or on the icon of interest, or on the field of the system switch are designed to execute only one program at a given time. Within Windows, the user can run several programs for parallel (independent) execution. Each running program has its own window. Switching between running programs is done using the mouse by fixing the cursor in the window of the desired program.
(buttons) . On the selected object it is necessary to call Related(or Mixed) documentation. This type of document allows you to coordinate the processes of making changes to the same objects different programs, as well as automatically propagate changes from one document to all related ones.
Comparison of Windows 3.1 with Windows 3.0
If you have experience working with Windows 3.0, mastering the next version 3.1 will not require much effort, since appearance and the control methods are practically the same. Most innovations come down to simplifying the service and eliminating management inconveniences. We are talking primarily about increasing the speed of work, simplifying the installation procedure, improving the formats of dialog boxes and increasing the efficiency and intelligence of the Print Manager.
I would like to highlight some of the innovations (long-awaited).
In the Windows 3.1 environment, you can compose documents from parts that are prepared in different applications, but the complexity of working with such a document is no greater than if it were prepared within a single application. So, working in new version Windows, when pasting into text prepared in Write, drawing created in Paintbrush, the drawing is considered as an object. It can be saved, downloaded and printed along with the document. The main feature of this linking of drawing and text is the ease of making changes. For example, working with text in the editor Write, It is enough to double-fix the cursor in the picture to call the graphic editor Paintbrush. The picture will be loaded into it automatically. All changes made to the drawing after this will be automatically displayed in the insert in text document. It seems that the text editor Write supplied additional features editing drawings (in full Paintbrush). Working with objects also includes operations with icons. Icons can be used inside documents to perform functions similar to those that these icons perform in the Windows environment.
Windows 3.1 shell does new technology working with a computer based on a graphical interface is more natural and clear. The mouse plays an even greater role here than in previous versions as the main tool for controlling the machine. In a number of cases, to invoke some (rather complex) operations, it is enough to simply “Drag and Drop” an icon or other object with the mouse. For example, to print a document, it is enough to use the mouse to “pull out” the icon of the corresponding file from the File Manager window and “put” it on top of the Print Manager icon. Drag a document file icon into an open editor window Write or editor window Notepad loads the corresponding document into the window.
Working with documents in general has been significantly simplified. We can talk about document-oriented organization of work. In this case, you can place an icon of a frequently used document in the Program Manager window and subsequently trigger the processing of this element (for example, editing) simply by double-fixing this icon. The same purpose is also served by the ability to automatically launch the File Manager after loading the shell - a field for selecting document files immediately opens in front of the user.
Subjected to significant processing and File Manager. Working with it has become significantly easier. At the same time, productivity and efficiency in the use of screen space have increased (it is possible to simultaneously observe larger number devices and directories).
Unlike previous versions Windows 3.1 can no longer work in the so-called real mode (Real Mode). This mode ensured that version 3.0 was compatible with earlier versions 1.X and 2.X (so that applications developed for these earlier versions shells, could be executed in the Windows 3.0 environment when running in real mode). In the same mode, Windows 3.0 could be used on machines with 8088/8086 processors. In shell version 3.1, the developers decided to say goodbye to the world of first-generation personal IBM-compatible machines (PC/XT). A prerequisite for installing the Windows 3.1 shell on a computer is an 80286 processor (preferably 386,486). When working in a Windows 3.1 environment, problems may arise with launching old (from versions 1.X, 2.X) applications. However, transferring applications from the 3.0 environment does not, as a rule, cause any complaints. In rare cases of "abnormal" behavior of applications from a 3.0 environment in a 3.1 environment, you have to contact the product vendors.
In the Windows 3 environment, a new set of fonts has been implemented - the so-called TgieTure-shrnft. These fonts are similar to PostScript fonts. but are easily adapted after a little adjustment to almost any type of printer. With a little effort you can be successful with these fonts in most Windows applications.
TrueType fonts can easily be scaled, deformed in various ways, rotated, etc. Additional comfort for those who like to select and create fonts is provided by a special program for demonstrating and using individual font characters - Charaker Map. Finally, the Windows 3.1 shell includes two small Multimedia programs (Multimedia). Their use requires special hardware support (acoustic adapter, possibly a CD-ROM drive). Using the mentioned programs called Sound Recorder And media player You can decorate the process of passing programs with sound effects. You can work with digital representations of speech and music, with pictures obtained, for example, from a video disc player.
For beginners, the system provides tutorial, which can be accessed already at the installation stage.
Windows applications
Windows - integrated program. Not only special programs designed for operation in the Windows environment (Windows applications), but also “regular” programs running in the DOS environment, the so-called, can run under the control of the Windows shell. DOS applications (DOS application programs). The Window shell provides efficient and comfortable exchange of information between separate programs performed under its control. Here we are primarily talking about Windows applications. The concept of integration is usually also associated with the ability to share computer resources between different programs. So, for example, a printer connected to a computer can be used with equal success by all programs on a competitive basis. Moreover, all operations associated with the need for recoding and driver changes (for example, when switching from printing texts to displaying illustrations) are taken over by the shell.
Most users are attracted to the Windows environment not only and not so much by the comfort of the shell itself, but by the specificity of the applications implemented in this environment. Features of the implementation in the Windows environment of even application programs familiar to users from working in DOS (applications) practically allow you to treat the Windows versions of these programs as completely new products.
Working in the Windows desktop and in Windows applications involves a kind of restructuring of your “lifestyle”. The user's "life" in the Windows environment is associated with "mouse" control, data exchanges between individual programs and parallel execution. Standardization of the interfaces of individual Windows applications makes it possible to easily move from one application to another without starting from scratch each time (at least in terms of methods and means of control).
In branded delivery Windows package There are several applications. They are all combined into a group Accessories(accessories, tools). These are small application programs in size and capabilities that make up the user’s “gentleman’s kit”. They are far from professional specialized packages. But they do a nice job of illustrating the capabilities of the shell and provide some minimal service. Moreover, it is very useful to start getting acquainted with serious packages with the corresponding tools of this group. So, for example, after working for some time with a text editor Write, in the future you can easily switch to using such professional word processing packages as Word for Windows, Lotus Ami Professional, WordPerfect for Windows" etc. In addition, in applications from the group Accessories Many new products have been implemented that are specific to latest version 3.1 Windows shell (working with objects, new fonts...).
Object-oriented approach creating Windows 95 Microsoft fully implemented the object-oriented approach. Since it was he who formed the basis of the new operating system, first let’s say a few words about what object orientation is.
The concept of “object-oriented” arose in programming relatively recently. When the computing power of machines was low, the creation of object-oriented systems was out of the question. The basis of everything was program code. Programmers wrote down sequences of commands to perform certain actions on data, which were compiled into modules and procedures. To work with each object, its own procedure was created.
Objects, their properties and methods Gradually, with the increase in the productivity of computing systems, the procedural approach began to be replaced by the object approach. The object came first, not the code that processes it. At the user level, the object approach is expressed in the fact that the interface is a semblance of the real world, and working with the machine is reduced to actions with familiar objects. So, folders can be opened, put in a briefcase, documents can be viewed, corrected, moved from one place to another, thrown into the trash, a fax or letter can be sent to the addressee, etc. The concept of an object turned out to be so broad that it has not yet received a strict definition.
An object, as in the real world, has various properties. A programmer or user can change not all properties of objects, but only some of them. You can change the name of an object, but you cannot change the amount of free disk space, which is also a property of the object. Properties of the first type in programming languages are called read/write, and properties of the second are called read only.
A method is a way of influencing an object. Methods allow you to create and delete objects, as well as change their properties. For example, in order to draw a point, line or flat figure on the screen, different sequences of codes or programs are compiled. The user, however, uses a single Draw() method to display these objects, which contains code to display all the objects with which he works. This convenience comes at the cost of the fact that object-oriented systems can only run on sufficiently powerful computing systems.
Procedural approach in early operating systems Until now, the procedural approach has prevailed in all operating systems. In order to perform any action in the system, the user had to call the corresponding program (procedure) and pass it certain parameters, for example, the name of the file being processed. The program performed the specified actions on the file and finished working. In this case, the user first of all dealt with the task of processing the document, and then with the document itself. In the old days, when computers were not personal computers, the user described the actions that a task was supposed to perform in some strange language called Job Control Language (JCL-Job Control Language).
With the advent of the terminal, the task management language was simplified and gradually turned into command line, however, the document processing procedure still came first, and the document itself played a supporting role.
The next stage in simplifying the work with the machine was the creation of various kinds of operating shells (first text), which “hid” the DOS command line from the user. Entering a sequence of characters that makes up an operating system command has been reduced to pressing a single function key or clicking a mouse. The most common of these “add-ons” to the operating system was the Norton Commander shell. However, the user’s main “tool” was still the keyboard. A qualitative transition occurred after graphical shells appeared. The user now primarily works with a pointing device such as a mouse, trackball or tablet rather than with a keyboard (of course, this does not apply to work within the applications themselves, e.g. text editors) . It does not need to remember almost any operating system commands. In order to launch an application, just click on its image or “icon” (the author prefers to call it an icon).
From a procedural approach to an object-oriented one In the early 90s. The procedural approach still predominates, but some signs of the object-oriented approach are emerging. For example, already in Windows 3+ you can assign an application for processing it to a specific document. At the same time, the object linking and embedding (OLE) method appeared, which allows you to implicitly launch the application that processes it by clicking on the image of an object, and after finishing processing, return to the previous application.
Closely related to OLE is the so-called in-place document editing method. If an object is embedded in a document that should be processed by a specific application, then when you click on this object, the desired application is implicitly launched, and nothing in the workspace changes except the toolbars. For example, if the text that is processed in the Microsoft Word editor has a table created in the editor Microsoft Excel, then clicking on it will replace toolbars Excel skills. The user can process the document with a completely different application without even knowing it. Another mechanism that simplified the work and brought closer the era of the object-oriented approach is called “Drag & Drop”, which literally means “drag and drop”. With this method, you click (usually the left mouse button) on an image of an object, move it around the screen while holding the button down, and release the button when the pointer is at the desired location on the screen. Thus, copy, move, and delete procedures became object-oriented.
What did the user do when he needed to delete files in the MS-DOS operating system? It launched the procedure for deleting files, passing their names as parameters: del FILEI. TXT FILE2TXT This action is in no way reminiscent of the real world, in which you simply throw unnecessary Papers into the trash. In the first place for the pass is the object (paper) on which the procedure is performed (transfer to the trash bin), R operating shells that work under Windows control 3.1, such an action has already been implemented as object-oriented - using the “Draw & Drop” mechanism. For example, in Norton Desktop, you can grab a file with your mouse and drag it to the trash can image. This is enough to delete the file. Thus, working on a personal computer is increasingly reminiscent of manipulating objects in the real world.
Selecting indicators and parameters for assessing OS Windows 95 - object-oriented OS Windows 95 is a full-fledged operating system Plug & Play 32-bit protected mode OS Priority multitasking Multithreading. Print spooler 32-bit installable file systems Facilities remote access Multimedia capabilities Support for MS-DOS applications Long filename support User Interface Working with memory
Comparative assessment of OS PVEM according to selected indicators Windows 95 compared to Windows 3+
The fundamental novelty of the Windows 95 operating system lies precisely in the fact that the concept of an object-oriented approach is most fully implemented in it.
Windows 95 - object-oriented OS
The object-oriented approach is implemented through the desktop model. Windows 95 does without the program manager familiar to Windows 3+. The user works with tasks and applications in the same way as with documents on his desk.
This is convenient for people who saw a computer for the first time, but creates some difficulties in the “transition period” for those who are accustomed to considering the program the basis of everything in the machine.
So, one of the main differences between Windows 95 and Windows 3+ (and from the vast majority of other operating systems) is that the main emphasis in it is on the document, and the program, task, application or program code is generally considered only as a tool for work with a document.
Windows 95 is a full-fledged operating system
Another fundamental Windows feature 95 is that, unlike Windows 3+, it is a “real” operating system (and not an operating shell running under MS-DOS). By “real” we mean that when you turn on the machine, Windows 95 boots immediately. This results in some inconvenience for the user. He must get used to the fact that before turning off the machine, he must gracefully shut down Windows 95, since the new operating system creates buffers in RAM and their contents must be flushed to disk.
Plug & Play
Approach to hardware has also changed dramatically. Now the system uses the Plug & Play standard (translated as “plug-and-play”, most often pronounced as “plug-n-play”), which facilitates and maximally automates the process of adding new peripheral devices. The Plug & Play standard is a joint development of Intel and Microsoft. Its main idea is that each device that complies with this standard reports certain information about itself, thanks to which the operating system automatically configures peripheral devices and resolves hardware conflicts. The Plug & Play standard must first be satisfied Motherboard BIOS boards and, of course, peripheral devices. Thus, the operating system provides automatic connection and device configuration that is Plug and Play compliant, maintains compatibility with legacy devices, and creates a dynamic environment for plugging and unplugging mobile components.
32-bit protected mode OS
MS-DOS was a pure 16-bit operating system and ran in real processor mode. In versions of Windows 3.1, some of the code was 16-bit and some was 32-bit. Windows 3.0 supported the real processor operating mode; when developing version 3.1, it was decided to abandon its support. Windows 95 is a 32-bit operating system that runs only in CPU protected mode. The kernel, which includes memory management and process dispatching, contains only 32-bit code. This reduces costs and speeds up work. Only some modules have 16-bit code for compatibility with MS-DOS mode. Windows 95 uses 32-bit code wherever possible, providing increased system reliability and resiliency. In addition, 16-bit code is used for compatibility with legacy applications and drivers.
Priority multitasking
Unlike previous versions, Windows 95 supports preemptive multitasking and parallel processes (multithreading). In Windows 3+, there was the so-called “preemptive multitasking” (non-preemptive multitasking), in which the application was responsible for distributing processor time. The system performed the task until the application “voluntarily” gave up the processor. In Windows 95, the system kernel is responsible for allocating processor time, which ensures normal operation of background tasks.
Multithreading
Windows 95 supports multithreading, a technology that allows it to properly multitask its own processes.
Print spooler
The print spooler has been radically redesigned compared to Windows 3+. Now, in parallel with printing, you can do something else (in the old shell you could either print or work). The print spooler is also now 32-bit.
32-bit installable file systems
This part of the operating system has become much more productive than similar components of Windows 3+. For hard drives virtual file allocation tables (vfat) are used, and for CDs the new CDFS (CD-ROM File System) file system is used. In this case, file names can contain up to 255 characters, including spaces and Special symbols(compatibility with the old file system has been preserved, although in a somewhat artificial way. Now, in most cases, the MSCDEX EXE module that performed the file system conversion is not required ISO standard-9660 (CD) to the MS-DOS file system.
An installable file system that displays file structure remote machine on network drive workstation is called a network redirector. Network redirectors for the IPX/SPX and NetBEU protocols also use 32-bit code. The NetBEU protocol is used when Windows work 3.1, a IPX/ SPX - for communication with machines running Windows NT, Remote Access Tools Windows 95, unlike most personal computer operating systems, was designed from the start to be networked, so file and device sharing is fully integrated into the interface. Windows user 95.
In Windows 95 you can access the network without installation network adapter! It will be replaced by a modem and a special PPP protocol (“point-to-point”, or “point-to-point protocol”). In this case, the operating speed is limited by the speed of your modem. The system provides advanced software for accessing the Internet, Microsoft Network, America Online and other similar services.
Multimedia capabilities
It is difficult to imagine a modern operating system without multimedia. To work with audio and video files of various formats, Windows 95 includes a set of codecs - effective software tools for compressing and decompressing these files and converting their formats for output to various devices multimedia (the word “coder” is an abbreviation for the words “coder-decoder”, just as “modem” is an abbreviation for the words “modulator-demodulator”). When playing a file, the system launches the encoder with which the file was created. Drivers sound cards use 32-bit code, but in cases where the system cannot recognize the card, the 16-bit real mode driver that comes with the card is used. When the 32-bit protected mode driver is running, the real mode driver is automatically disabled.
When you insert a CD into the reader, the system tries to recognize its format and launch the appropriate application to play it. If an ISO-9660 (software) disk is installed, then Windows 95 looks for a file called AUTO-RUN. INF u executes it. This mechanism is called Spin & Grin.
The code responsible for image processing has been significantly redesigned. so the playback quality AVI files has increased significantly compared to Windows 3+, and the speed of their playback is now almost independent of the selected image scale. Built-in audio, video and CD capabilities will give new impetus to the development of multimedia applications. Windows 95 is the first Windows version, which challenges MS-Dos in gaming software support.
Support for MS-DOS applications
Windows 95 takes up less space in main memory, so you can now run many of those MS-DOS programs that couldn't run under Windows 3.+. Programs that will not fit into memory even now can be baked into emulation mode MS-DOS. By switching to this mode, Windows 95 terminates all running applications, and then deletes itself from memory, leaving only a small boot module. Once you've finished working with an MS-DOS program, you can return to Windows with the press of a single key.
Long filename support
You can forget about restrictions on file name length in Windows 3.+ and MS-DOS systems. In Windows 95, file names can be up to 255 characters long.
User Interface
Thanks to the new interface in Windows 95, compared to Windows 3. +, it is much easier to launch programs, open and save documents, work with disks and network servers.
Work with Windows memory 95 automatically frees all memory allocated to the application after it finishes running. In Windows 3+, poorly written applications often freed not all the memory they requested. From time to time, memory turned out to be so low that the only solution was to restart the system (and sometimes reboot the machine). This kind of trouble is called “memory leak” and happens to software products of even the most famous companies. When you terminate an application in Windows 95, all the memory it occupied is freed automatically and such problems do not occur.
Prospects for the development of OS PVEM Windows NT
At the moment, the global computer industry is developing very rapidly. System performance increases, and therefore the ability to process large volumes of data increases.
Operating systems of the MS-DOS class can no longer cope with such a flow of data and cannot fully use the resources of modern computers. Therefore, recently there has been a transition to more powerful and advanced operating systems of the UNIX class, an example of which is Windows NT, released by Microsoft.
Tasks set during the creation of Windows NT
Windows NT is not a further development of previously existing products. Its architecture was created from scratch, taking into account the requirements for a modern operating system. Peculiarities new system Developed based on these requirements are listed below.
1. Striving to provide compatibility(compatible) of the new operating system, the developers of Windows NT retained the familiar Windows interface and implemented support for existing file systems (such as FAT) and various applications (written for MS - Dos, OS/2 1. x, Windows 3. x and POSIX) . The developers also included in Windows NT tools for working with various network tools.
2. Achieved portability(portability) of a system that can now run on both CISC and RISC processors. CISC includes Intel compatible processors 80386 and higher; RISC is represented by systems with MIPS R4000, Digital Alpha AXP and Pentium series P54 and above.
3. Scalability(scalability) means that Windows NT is not tied to a single-processor computer architecture, but is capable of taking full advantage of the capabilities provided by symmetric multiprocessor systems. Currently Windows time NT can operate on computers with a number of processors from 1 to 32. In addition, if the tasks facing users become more complex and the demands placed on the computer environment expand, Windows NT makes it possible to easily add more powerful and productive servers and workstations to the corporate network. Additional benefits allows the use of a single development environment for both servers and workstations.
4. Windows NT has a homogeneous security system(security) meeting US government specifications and complying with B2 security standard. In an enterprise environment, critical applications are provided with a completely isolated environment.
5. Distributed Processing(distributed processing) means that Windows NT has built-in processing networking opportunities. Windows NT also allows communication with different types of host computers by supporting a variety of transport protocols and using high-level client-server facilities, including named pipes, remote procedure calls (RPC) and Windows sockets.
6. Reliability and fault tolerance(reliability and robustness) provide architectural features that protect application programs from damage by each other and the operating system. Windows NT uses fault-tolerant structured exception handling at all architectural levels, which includes a recoverable NTFS file system and provides protection through built-in security and advanced memory management techniques.
7. Opportunities localization(allocation) provide tools for working in many countries of the world in national languages, which is achieved by using the ISO Unicod standard (developed by the international organization for standardization).
1. Thanks to the modular design of the system, it is ensured expandingbridge(insibility) Windows NT, which, as will be shown in the next section, allows the flexibility to add new modules to different levels of the operating system.
List of used literature
1. “IBM PC for users” V. E. Figurnov
2. “Windows 95 for busy people” Ron Mansfield
3. “Windows 95 operating system” A. V. Potapkin
4. “Young Fighter Course” K. Akhmetov
5. “Effective work in Windows 95” K. Stinson
6. “Windows 3.1” Stefan Feutz
