Ms dos version 3.0. "History of MS-DOS. And yet the games

Good day.

If you are interested in the DOS operating system, what it is, by whom and in what cases it is used, you have come to the right place. In my article you will find answers to these questions and find out how DOS differs from the familiar and beloved Windows system.

Acquaintance

This abbreviation stands for Disk Operating System in English, and in our opinion it is a disk operating system. It includes a whole family of operating systems for PCs, which involve the use of disk drives, that is, hard drives and floppy disks.

The first version was released by Seattle Computer Products in 1980. Later, the product was bought by Microsoft Corporation, signing a contract with IBM that included the development of an operating system for a new model of computers from this company.

Nowadays DOS is rarely found, except for working with outdated equipment or programs written a long time ago. It was popular during the advent of computers. Although there are extenders that allow you to fully use this product today.

Comparison with Windows

In order for you to better understand the essence of our conversation, I will make a comparison with Windows, since this system is one of the most popular. I won’t go into the weeds, but I’ll just say the main thing.

In the 80s of the last century, computers were not as compact as they are now, but were large electronic computers. Despite their size, their functionality was not very diverse. Therefore, a single-tasking 16-bit with a simple interface was enough for them.

Didn't understand the last sentence? This means that in DOS you cannot work in multiple windows and programs, as Windows allows, which, by the way, has , and therefore can quickly process more commands.

The appearance of DOS is much simpler than that of beautiful and colorful Windows with many different icons and buttons.

The old brother's shell is similar to the command shell Windows line. That is, it did not have a graphical interface.

Also in mind rapid development technology, disk system does not cope well with current sound, video cards and other hardware. It also does not involve means of control and protection against viruses, since at the time of its popularity, they essentially did not exist. While Windows is adapted to modern requirements.

In favor of disk operating systems

From point of view regular user, Windows wins due to the above advantages. However, there are times when none of them matter. For example, for an accountant who does not need to switch between windows, it is more convenient to work in MS-DOS. Since the interface allows you to preserve your vision, or rather strain it less.

And many experienced programmers prefer the outdated system. Because its simplicity allows you to completely take control over it into your own hands. To perform basic functions, it only needs a few light files, while in Windows there are quite a lot of them and all the most important things, especially , are reliably hidden from the user.

DOS components

This OS includes:

Basic input/output system (). Built into the permanent memory of your hardware. Needed to check the functionality of the hardware when starting the computer and calling the initial DOS startup block.
Block bootstrap(Boot Record) - a lightweight program (no more than 512 Bytes). After the BIOS, she loads two more modules to finally turn on the system.
BIOS expansion module (IO.SIS). Its functions include setting up the OS configuration and installing drivers.
Interrupt handling module (MS DOS.SYS) - maintains the file system (FAT with a limit of 8 characters for file and directory names), and is also responsible for data input/output.
Command processor (COMMAND.COM) - processes tasks that you give.

Built-in drivers for the operation of a mouse, keyboard, drive, etc.
Utilities necessary to perform various service functions (format a disk, etc.).

I think the above information is sufficient for general information.

Have a good mood!

We are accustomed to the fact that when working with a computer, we see on the display high definition a comfortable “desktop” surface with “folders” and “documents” laid out on it. We have a separate window for each running program and each document, and we control all of this using a hand-held manipulator, which for some reason is called a “mouse”. Nothing prevents us from launching several programs and switching between them, working simultaneously with several documents different types. We don't think about the fact that this type of computer-user interaction was developed only three decades ago, and that it is called a graphical user interface. (Not to mention that today it is extremely easy to connect a computer to various types of networks and supports a colossal number of types of external devices.)

And of course we don’t think about the fact that for only thirty years users controlled the computer using commands entered from the keyboard, and the computer - more precisely, the MS-DOS operating system - responded to erroneous commands by producing obscure letters in poisonous green letters. text messages, For example:

Not ready reading drive A
Abort, Retry, Fail?

Bad command or file name

Programs had to be loaded one at a time (MS‑DOS did not have multitasking capabilities), they had a lot of compatibility problems and a very varied user interface. But those who didn't like it could return to the typewriter and ink drawing. And there were fewer and fewer such hunters - the ability to save documents in the form electronic files and then reusing and modifying them, rather than reprinting them as carbon copies all the time, opened up great prospects.

To understand why the MS‑DOS operating system was exactly the way it was, how it became a kind of springboard for Microsoft Windows, and why, in its various guises, it existed for two whole decades, let’s fast forward another decade back, to 1971.

Before MS-DOS

In 1971, Intel, commissioned by the Japanese company Busicom, released integrated circuit 4004 - the first microprocessor, functionally similar to the modern central processor that underlies any computer, but much less powerful - it was four-bit, i.e. could only handle four-bit binary numbers, zero through 1111 (decimal 15), and had a clock speed of less than 1 MHz. Just a year later, the first eight-bit microprocessor, the 8008, appeared, and the 2 MHz 8080 microprocessor, released by Intel in 1974, was already so powerful that it could be used to build small computer. This is what MITS did, which released the world's first PC, Altair 8800, in 1975.

It was followed by PCs from other companies, which also used eight-bit microprocessors from Intel and other manufacturers - Motorola, Zilog. Unlike professional computers that ran UNIX, PCs used Digital Research's CP/M (Control Program for Microcomputers) operating system, the first OS to run on PCs from various manufacturers. To others software, which worked on almost all PCs that existed at that time, was a translator of the Basic programming language, released by the young company Microsoft.

The Rise of MS-DOS

In 1980, IBM decided to enter the PC market, and in 1981 the IBM Personal Computer model was released, created by the IBM entry-level systems department under the leadership of Philip Donald Estridge - the great Don Estridge (1937-1985), now revered as a father IBM PC. To minimize time and costs, the developers used an open architecture. The IBM PC was designed using independently manufactured components. Basic model The IBM PC had 64 KB of RAM, expandable to 256 KB. The brain of the IBM PC was the new 16-bit microprocessor 8088 from Intel. Hardware documentation and software specifications were published.

When IBM approached various software firms about its new PC project in October 1980, Microsoft could not offer IBM its own OS. However, Digital Research only had the CP/M-80 available for 8-bit computers. While Digital Research was working on the 16-bit CP/M-86, Microsoft acquired the rights to the 16-bit 86-DOS system from Seattle Computer Products.

One of important qualities 86‑DOS had easy portability of programs from the CP/M‑80 environment. It also borrowed many of the CP/M commands, such as REN (rename file), DIR (display directory contents), and TYPE (display file contents). A significantly revised version of 86‑DOS was called MS‑DOS 1.0. Deliveries began in August 1981 IBM computers PC with this OS called PC‑DOS 1.0. In addition, Microsoft received the right to sell licenses for MS‑DOS to other PC manufacturers.

The abbreviation DOS (Disk Operating System) emphasized the main purpose of this operating system - to provide disk I/O control. MS-DOS did not have built-in support for tape drives or local area networks. The main thing it provided was working with files. For ease of use of files, MS‑DOS allowed them to be given names up to eight characters long, with a description (extension) of up to 3 characters, for example DOCUMENT.TXT or READ.ME.

MS‑DOS 1.0, quite progressive compared to CP/M, used more advanced methods for managing disk data and had a wide range of commands for service programs. Since the original IBM PC came with 160-kilobyte floppy disk drives, PC-DOS 1.0 only supported such media. Other PC manufacturers did not adopt PC-DOS until PC-DOS 1.1 was released in May 1982, allowing it to work with 320 KB floppy disks. That's when Microsoft was able to exercise its right to sell licenses for MS‑DOS - a month later the same version of the OS was released under the name MS‑DOS 1.25, and Texas Instruments, Compaq Computers and other companies that began manufacturing began to use it IBM PC-compatible computers.

MS‑DOS 2.0 (March 1983) supported 360 KB floppies and 10 MB hard disks(especially for the new IBM PC XT computer) and provided the ability to sort files into directories. It was then that the global boom in the production of IBM PC-compatible computers began - such respectable companies as Tandy, Hewlett-Packard, Digital Equipment Corporation and others joined the list of manufacturers of these machines. MS‑DOS 2.11 became the base OS for the products of many companies - the most stable implementation of the second generation of MS‑DOS.

MS‑DOS 3.0 (August 1984) was aimed at new model IBM computers - IBM PC AT - the first computer based on the Intel 80286 microprocessor, with a 5.25‑inch high-density floppy drive (for 1.2 MB floppy disks) and 20 MB hard drive. MS‑DOS 3.2 (December 1985) supported 3‑inch 720 KB floppies and hard drive logical partitions up to 32 MB. The system continued to evolve, adding more and more capabilities to support national currency and time images, character tables, and keyboard layouts.

The popularity of the IBM PC platform also grew, there were more manufacturers of IBM PC-compatible machines, and the number of software developers for the IBM PC exceeded all conceivable limits. In 1986, an IBM PC-compatible computer from Compaq Computer, based on the 80386 microprocessor, had already appeared. The following year, IBM also had a computer with an 80386 microprocessor - PS / 2 Model 80. MS‑DOS was not able to fully exploit the capabilities of the new computers. So, if computers with an 8086 microprocessor were produced with no more than 640 KB of RAM, then on the 286th computer it was theoretically possible to install up to 16 MB of memory, and on the 386th - up to 4 GB. MS‑DOS could never use more than 640 KB of memory.

However, the growing market demanded intensive production of IBM PC-compatible machines, even more intensive improvement of MS-DOS, and perhaps even more intensive release of professional applications for the IBM PC and MS-DOS. One of the main requirements was compatibility: all new versions of MS-DOS had to work successfully with programs released for older versions of MS-DOS.

Therefore, in MS‑DOS 3.3 (April 1987) there was nothing fundamentally new, but everything old was improved. In particular, version 3.3 supported the new 3‑inch 1.44 MB floppy disks. MS‑DOS 3.3 became the most important stage in the history of MS‑DOS development; the following versions MS‑DOS 4.0 and MS‑DOS 4.01 (1988) did not attract much attention from buyers. Most IBM PC users remained faithful to MS‑DOS 3.3.

The emergence of Windows

As we have already noted, MS‑DOS had a very primitive user interface: in order to load a program or perform other operations, the user had to type commands on the keyboard. For example, the command to copy from the DOC\WORK directory of drive C: to drive A: all files and directories, except those that are already there, looks like this:

REPLACE C:\DOC\WORK\*.* A:\ /S /U

In 1985, Microsoft released the first version of Windows, a graphical MS‑DOS shell that offered the user a windowed interface. To use everything Windows benefits, the program must be designed specifically for Windows.

The IBM PC-compatible computers that existed at that time, however, did not have enough power to ensure full functionality graphical environment. Therefore, the Windows that was made in 1985 looked rather pale. But Microsoft continued to invest in Windows. In 1987-1988 Various implementations of Windows/286 and Windows/386 (Windows 2.x) appeared.

Designed to run on appropriate microprocessors, they were already quite functional. Finally, in May 1990, an event occurred that largely determined the current state of the hardware and software market for IBM PC-compatible computers.

Windows 3.x

Windows 3.0, released in May 1990, booted under MS-DOS, but made you forget about MS-DOS immediately. Access to the entire amount of computer memory was carried out through the MS‑DOS driver HIMEM.SYS and special system"MS‑DOS extensions". This led to a qualitative leap - a completely graphical window interface combined with multitasking capabilities. Windows multitasking did not allow you to control the work of programs as flexibly as OS/2 multitasking, but it required less memory. On computers with an 80386 microprocessor and higher, Windows 3.0 ran with virtual memory, i.e., it used part of the disk as an extension of RAM.

To launch programs, the Program Manager application was used. To help you organize and store launch icons for large quantities applications, the developers have made the File Manager multi-window. For operations with files and disks, Windows 3.0 included a multi-window program called File Manager, which allowed many file operations to be performed using the drag-and-drop method.

MS-DOS logo from the MS-DOS 6.0 box

MS-DOS mode icon from Windows 95 operating system

The range of services provided by Windows has led to the fact that all promising programs began to be developed taking into account the requirements of Windows. MS-DOS was now primarily expected to be a strong support for Windows, and in June 1991, MS-DOS 5.0 was released, designed to work better with Windows 3.0. It included, for example, a new version of HIMEM.SYS. To illustrate the benefits of multitasking, MS‑DOS 5.0 shipped with the MS‑DOS Shell with a program switching subsystem borrowed from Windows 3.0.

In April 1992, Windows 3.1 went on sale. From now on it is called the operating system. Strictly speaking, this environment could not function independently, without MS‑DOS. But this does not change the state of things. A little later, Windows 3.1 for Workgroups was released to work with peer-to-peer local networks, and a year later - Windows 3.11, almost identical to Windows 3.1, and Windows 3.11 for Workgroups. These versions of Windows have many improvements over Windows 3.0.

In 1993–1994 Several new versions of MS‑DOS were also released. The most significant feature of MS‑DOS 6.0 (April 1993) was the presence of a large collection of original and licensed utilities, in including Microsoft DoubleSpace to increase the usable capacity of disks by dynamically compressing data. In version MS‑DOS 6.2 (October 1993), the Microsoft DoubleSpace program was improved, from version MS‑DOS 6.21 it was removed due to legal conflicts with Stac Electronics, the manufacturer similar program Stacker, and in version MS‑DOS 6.22 (both - 1994) - replaced by DriveSpace, which did not cause any complaints from the Stac company. And this was the last standalone version of MS‑DOS.

Windows 9x

Subsequent MS-DOS versions were included with the latest versions of Windows.

The partially 32-bit operating system Windows 95, released by Microsoft in the late summer of 1995, had internal MS-DOS 7.0, it could be used to support programs that were incompatible with the new version of Windows, but by default it would immediately load on users' computers. graphical interface.

Why was it so important to lure users away from MS‑DOS? The new generation of Windows provided more high reliability and more stable and consistent application concurrency than Windows 3.1. Windows 95 made better use of memory and disks, and also allowed file names of up to 255 characters. The system supported the Plug and Play automatic hardware configuration specification, which allowed automatic detection and configuration of most existing hardware for IBM PC-compatible computers. Windows 95 worked with all types of gaming and multimedia devices that existed at the time of the OS's release.

Windows 95 was the first system that, on the one hand, was designed to run 32-bit programs, and on the other, worked with 16-bit Windows 3.1 programs and almost any MS-DOS program. The ultimate goal was to get rid of 16-bit code and completely move the entire market to 32-bit applications and operating systems. It was for this purpose that the branch of Windows NT developed in parallel - modern, fully 32-bit operating systems for business.

During 1995-1998 Microsoft constantly updated Windows 95, and in 1998 it released Windows 98, which had an improved interface, a new file FAT system 32, and supported a unified model of device drivers for Windows and Windows NT (Windows Driver Model), as well as new types of hardware, including universal port Universal Serial Bus (USB), etc. The integrated version of MS‑DOS was numbered 7.1.

The two thousandth versions of Windows for home (Windows Millennium Edition, or Windows Me) and Windows for business (Windows 2000) were very similar in appearance. At the same time, Windows 2000 almost provided the necessary flexibility in using a variety of software (including computer games and multimedia) and when selecting equipment, and MS-DOS was almost excluded from Windows Me - only the bootloader with internal number version 8.0.

With this, the adventures of MS-DOS and the history of two parallel branches of Windows ended, and a new era began - next version Microsoft's operating system became Windows XP.

In conclusion, we note that at different times different companies released their own versions of MS‑DOS-compatible operating systems. These were not only versions of DOS intended by manufacturers for installation on PCs of their own production, such as Compaq DOS, Zenith DOS or early versions PC‑DOS from IBM. Individual versions of DOS were released for general sale to compete with Microsoft's MS-DOS. These include DR DOS from Digital Research, Novell DOS 7.0 (the latest version of DR DOS released after Digital Research was acquired by Novell), later versions IBM PC‑DOS, PTS‑DOS from the Russian company Fiztekh-Soft, etc.

And most importantly. Operating value MS-DOS systems difficult to overestimate. It controlled computers with microprocessors with a clock frequency of less than 5 MHz, a RAM capacity of up to 640 KB, and such small hard drives, which would not fit even a single photograph taken by a modern professional camera. Today we work on personal computers with 32- and 64-bit architectures, the microprocessor frequency of which is measured in gigahertz, the amount of RAM is measured in gigabytes, and the capacity hard drive- hundreds of gigabytes, but reliable, unpretentious workhorse MS‑DOS carried out the entire computer revolution. Millions of people became users and programmers of personal computers with this operating system.

Kamill Akhmetov
Microsoft Technology Officer

Topic 1.3: System Software

Topic 1.4: Service software and algorithmic basics

Introduction to Economic Informatics

1.3. PC system software

1.3.4. Operating system MS DOS

One of the most common operating systems until the mid-90s was Microsoft's disk operating system MS DOS (Microsoft Disk Operating System).

In modern Windows operating systems, to work with DOS commands, the command line is used, which can be called: Start/Run, enter cmd in the dialog box and click OK. Another way to open the command line is Start/Programs/Accessories/Command Prompt.

Composition of MS DOS

The MS DOS operating system includes the following main modules:

Basic input-output system (BIOS).
Boot Record block.
BIOS expansion module (IO.SIS).
Interrupt processing module (MS DOS.SYS).
Command processor (COMMAND.COM).
driver files, which, after being loaded into memory, ensure the operation of devices such as a mouse, CD-ROM, etc.
OS utilities that perform various service functions (disk formatting, etc.).

The basic BIOS system is hardware dependent and is located in the ROM memory of the PC. This part of the operating system is built into the PC.

It implements the following main functions:

Automatic check hardware components when turning on the PC.
Calling the OS boot block (loading the operating system program into memory occurs in two stages: first, the boot record block is loaded and control is transferred to it, then the remaining modules are transferred using this block).

The Boot Record is a very short program (about 512 bytes) found in the first sector of every DOS disk. Boot Record loads two more OS modules into memory (system files io.sys, msdos.sys), which complete the DOS boot process.

The IO.SIS BIOS extension module is an addition to the BIOS ROM. It configures the OS for a specific PC configuration and allows you to connect new drivers to non-standard I/O devices.

MS DOS.SYS interrupt handling module – implements services related to servicing the file system and input/output operations.

Command processor COMMAND.COM – processes commands entered by the user.

Loading MS DOS

After turning on the power of a computer on which the MS DOS operating system is installed, the following processes automatically occur:

PC testing (BIOS runs a set of initial computer testing programs);
loading MS DOS (reading the operating system from an external storage device into RAM);
MS DOS setup (OS setup is performed using commands written in the config.sys and autoexec.bat files).

After loading the OS, a prompt is displayed on the monitor screen for the user to enter commands, which consists of the disk name and the following symbols:
A:\> or C:\>.

This means that DOS is ready to receive commands.

The DOS prompt contains information about the current drive and the current directory. For example,
A:\>- drive A:, root directory:
C:\windows>- drive C:, windows directory.

The disk it works with this moment PC is called current.

Entering and editing commands

To enter a command, type this command on the keyboard and press Enter. To edit the entered command, you can use the following keys: Backspace, Delete, Ins, Esc, Cursor keys.

General purpose commands:

VER – check the OS version (A:\>VER, press Enter);
CLS – clear screen (A:\> CLS, press Enter);
TIME – check and correct the system clock (A:\>TIME, press Enter);
DATA - check and correct the system calendar (A:\> DATA, press Enter).

Basic commands for working with files, directories, disks

Working with files:

Creation text files: A:\>copy con (file name) – after entering this command, you will need to enter the lines of the file one by one. At the end of each line, press the Enter key, and after entering last line– press F6 (or Ctrl +Z) and then Enter. A file with specified name;
copy file: A:\>copy a:\lesson urok (copy lesson from root directory to the urok directory);
delete file: A:\>del less, press Enter;
rename: A:\>ren lesson conon, press Enter (the renamed file is conon);
displaying the file on the screen: TYPE example: A:\>TYPE prim.1, press Enter;
merging (combining files into one) COPY_full name of the 1st file + full name of the 2nd file _full name of the 3rd file, press Enter.

Working with directories:

create a directory: A:\>md urok, press Enter;
delete directory: A:\>rd urok, press Enter;
directory browsing (directory table of contents): A:\>DIR, press Enter;
change the current directory: A:\>cd urok, press Enter. We get: A:\urok> (drive A:, directory \urok);
going to the root directory: A:\urok>cd .. , press Enter. We get: A:\> (drive A:, root directory);
displaying a list of disk directories: A:\>TREE A: /F, press Enter.

Working with disks:

moving from disk to disk: C:\ windows >A:, press Enter, we get A:\>;
format disks: C:\> format a:, press Enter;
specifying a label on the disk: A:\vol, press Enter;
reading the label: A:\label, press Enter.

The system software of each computer can be divided into two components - operating system (OS) and system software packages. Some of the system programs required by a computer are built into the machine, and specifically into a part of the computer called read-only memory (ROM). ROM programs are read-only. These system programs that monitor, assist and necessary services application programs are called basic input/output system (BIOS). Operating systems are examples of higher-level system programs. operating system - a set of programs that, interacting, jointly manage computer (system) resources and processes that use these resources when executing application programs.

Main OS functions:

Testing (checking the correct functioning) of hardware;

Deciphering and executing commands coming from the user (from the keyboard) or from RAM;

Control of the operation of all devices and computer blocks;

Memory resource allocation;

Providing the ability for several users to work on one computer;

Protection of software from outside influence;

Maintenance of interruptions in hardware operation.

Purpose and characteristics of MS DOS. MS DOS versions; MS DOS composition;

MSDOS – Microsoft Disk Operating System, i.e. disk operating system from Microsoft. operating system MSDOS is the simplest operating system for IBMPC computers. It is used on all junior models of IBMPC and can be used on all older models of computers of the same type.

The first version of MS DOS had much more modest capabilities than modern operating systems. It was single-user, supporting only disk drives, a keyboard, and an alphanumeric display. But it was compact, had rather modest requirements and performed the necessary minimum functions for users and programs. Over time, many changes were made to MS DOS:

Support for new devices (hard drive, CDs, extended memory, etc.) was added, and the ability to support any other devices using software drivers was also provided;

Hierarchical support included file structure on floppy disks and hard drives;

Support for national keyboards and alphabets is provided;

Numerous new user features are included.

MS DOS remained a single-tasking OS;

It turned out to be impossible to build into MS DOS reliable means for protecting data from unauthorized access and organizing collective work with data;

DOS programs can only be executed within the first MB of memory, and the rest of the memory can only be used for data storage.

OVERVIEW OF MS DOS VERSIONS

Versions 1.x : Very similar to OS CP/M. Only single-sided floppy disk format with a memory capacity of 160 KB (8 sectors, 40 tracks, sector size 512 bytes) was supported. Starting with version 1.25 (PC DOS 1.0), which appeared in May 1982, a double-sided floppy disk format with a memory capacity of 320 KB was introduced.

Versions 2.x : March, 1983 Additional features: working with hard drives (HDD); hierarchical file system structure; I/O redirection tools (borrowed from UNIX); the concept of installable peripheral device drivers, which made it possible to quickly adapt the OS to various hardware configurations; 360 KB floppy disk format (9 sectors, 40 tracks, sector size 512 bytes)

Versions 3.x : August, 1984 Additional features: 1.2 MB floppy disk format,

3.5" floppy disks (720 KB format) (starting from version 3.2), partitioning the HDD into logical disks (up to 32 MB in size), which made it possible to use HDDs larger than 32 MB in size, improved support for national character sets. Support for computer networks (weak , starting from version 3.1), commands (programs): LABEL, ATTRIB, commands (programs): XCOPY, REPLACE (starting from version 3.3),

MS DOS 3.3 is by far the most widely used on the IBM PC XT and the IBM PC AT-286 with a memory capacity of no more than 640 KB.

Versions 4.x : November, 1988 Additional features: support for graphic Video Adapters EGA, VGA, logical disk capacity - more than 32 MB, support for the LIM / EMS standard, which allowed certain parts of MS DOS to be loaded into additional memory,

Dos-Shell shell program. Despite this, MS DOS versions 4.x are not widely used.

Version 5.0 : July, 1991 Additional features: efficient use RAM, additional utility programs, the ability to load the MS DOS kernel into HMA memory (High Memory Area) on the IBM PC AT-286 and higher, the ability to load peripheral device drivers into UMB memory on the IBM PC AT-386 and higher,

up to 620 KB of address space (0-640 KB) of RAM is allocated for application programs,

HDD support up to 2 GB, 2.88 MB format for 3.5" floppy disks

Version 6.0 : March, 1993 Additional features: efficient use of RAM, additional utility programs, software for optimizing the file system on logical disks (DEFRAG), commands (programs) that have lost their relevance have been removed, special. MEMMAKER program - optimization of the location of resident programs in RAM, multi-configuration files ONFIG.sys, virus protection system (weak), increasing available disk space (DoubleSpace),

means for regulating PC power consumption (LapTop, NoteBook)

Version 6.2 : October, 1993. All improvements are in the area of increasing the reliability of working with data at the file system level. Additional features: increased efficiency of existing commands (programs), CD-ROM caching, rejection of DoubleSpace without loss of information, identification and bypass of physical defects of HDD and FDD, identification and elimination of defects in the file system, including “compressed” DoubleSpace, step-by-step execution of any *.bat file, including AutoExec.bat,

What does the MS-DOS operating system consist of?

The MS-DOS operating system consists of many different files. They include the actual operating system files IO.SYS, MSDOS.SYS and 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 the extension basic system input/output 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. So called internal teams- 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, a new disk device may have a different number of tracks and sectors, and 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 operating system files IO.SYS, MSDOS.SYS and COMMAND.COM must be written to a specific location on the disk. They do not need to be copied to other directories on the disk.

The loading process is carried out as follows. First, the system start record is loaded into memory, then - system files IO.SYS, MSDOS.SYS and COMMAND.COM.

When the machine is turned on (or the system is restarted), control is transferred to the ROM program (memory read only). The program checks the correct structure of the operating system startup record on the system disk. If the entry is found and does not contain errors, then it is loaded into memory and receives control.

The start entry checks whether the IO.SYS and MSDOS.SYS files are the first files on the disk. If the test result is positive, then the files are loaded into memory, and the free section with the lowest address is selected. Control is then transferred to the initialization module of the IO.SYS file. If the files are written in a different location or are not on the disk, a message appears on the screen:

Non system disk Replace and press any key

The initializing module transfers control to the MSDOS.SYS file, which determines the initial parameters of the disk buffer and data control block area used when executing service programs. File programs also determine the status and initialize the computer's electronic equipment. After this, control returns to the initializing module IO.SYS.

The initializing module checks for the presence of the CONFIG.SYS file in the root directory of the system disk. If a file is found and contains data about available drives, then the specified drives are stored in memory.

Files One of the main responsibilities of MS-DOS is the maintenance (storage, creation, destruction, etc.) of files. A file in MS-DOS is similar to any file. This is a set of interrelated data located in a specially designated place. Unlike ordinary documents stored in special archive folders or safes, MS-DOS files are stored on disks. When a file is processed, it is loaded into the machine's RAM. Both loading into memory and storing files are functions of the operating system.

File identification Every file in MS-DOS must have a name. The file name can be simple or complex. A complex name consists of a base (simple) name and an extension. The file is recognized by the operating system by its name. The names of some files, for example those on the system floppy disk, are predefined. They are reserved by the operating system. The names of the remaining files are assigned by the user. Usually they try to come up with a name that reflects the purpose of the information inside the file. The extension is used to indicate the type of file, for example, text or data file. It can also serve to identify files with information similar in meaning, for example, to differentiate files with personal and business correspondence. When a file is written to disk, its name is automatically placed in an area of disk memory called a directory (or directory).

File serving in MSDOS The file management system in MS-DOS is built on the use of directory (or directory) data on the disk. A directory is an area of memory on a disk that is allocated during the formatting process. A directory is a table where data about files stored on disk is entered. Each file in the directory corresponds to one entry. The directory entry includes the following information: the full name of the file (name and extension), the date and time of its creation or last modification, the amount of memory occupied in bytes, as well as some additional information used when servicing the file by the operating system .

Tracks and sectors In order for data to be written to a disk, its surface must be structured - i.e. divided into sectors and tracks. TRACKS are concentric circles covering the surface of the disk. The track closest to the edge of the disk is assigned the number 0, the next one - 1, etc. If the floppy disk is double-sided, then both of its sides are numbered. The number of the first side is 0, the number of the second is 1.

Each track is divided into sections called sectors. Sectors are also assigned numbers. The first sector on the track is assigned the number 1, the second - 2, etc. Typically a sector takes up 512 bytes.

Hard disks A hard drive consists of one or more round platters. Both surfaces of the plate are used to store information. Each surface is divided into tracks, the tracks, in turn, into sectors. Tracks of equal radius form a cylinder. Thus, all zero tracks make up cylinder number zero, tracks number 1 make up cylinder number 1, etc.

File and directory allocation table The FORMAT command creates a file allocation table (FAT) and disk directories. Both of these structures are closely related to the organization of access to files. There are two copies of FAT on each drive. This table is of exceptional importance when serving files, so if the first copy of FAT is lost, the system gains access to the second.

On a standard floppy disk with 8 sectors per track, FAT occupies 1 sector. On a standard floppy disk with 9 sectors, 2 sectors are allocated per track for the table.

Directory structure A directory is a table describing the contents of a disk. Each file in the table corresponds to one entry. A record occupies 32 bytes, divided into 8 sections or fields. Each field records information used by the system when servicing the file.

System file maintenance MS-DOS provides two file serving technologies. The first was developed during the creation of versions 1.X. This technology is based on the use of data structures called file control blocks (FCB). At that time, the vast majority of computers ran the CPM operating system. FCB blocks ensured compatibility of MS-DOS files with files of this system. During the development of MS-DOS versions 2.X, when a hierarchical file organization structure was proposed, a second technology for maintaining them was developed. It is based on the use of references to the file control record and does not require the organization of an FCB. After this technology was tested in the operating room UNIX system, it has become widespread.

Memory organization

Memory consists of a large number of individual elements, each of which is designed to store a minimum unit of information - 1 byte. Each element has a unique numeric address. The first element is assigned address 0, the second - 1, etc., including the last element, whose address is determined by the total number of memory elements minus one. Typically, the address is specified by a hexadecimal number (in the text, hexadecimal numbers are marked with a capital “H”, for example, 10H).

Segments A computer's processor (CPU) divides memory into blocks called segments. Each segment occupies 64 K and each segment has a unique numeric address. The processor has four segment registers. A register is an internal structure designed to store information. Segment registers are designed to store the addresses of individual segments. They are called CS (Code Segment), DS (Data Segment), SS (Stack Segment) and ES (Spare Segment). In addition to those indicated, the processor has 9 more registers. At this point, the IP (instruction pointer) and SP (stack pointer) registers should be noted. The CS and IP registers paired together make up the long address of the instruction that will be executed next. The SS and SP registers in pairs make up the long stack address.

Memory access Access to memory cells is carried out by connecting the contents of a segment register with the contents of one or another register. In this way, the address of the required memory area is determined. For example, the address of the next instruction is determined by the contents of the CS and IP registers (written “CS:IP”). After a command is executed and removed from memory, the contents of IP are changed so that the CS:IP registers contain the address of the command that will be executed after this one. The method of combining registers to determine the address of a memory cell does not impose restrictions on the amount of available memory. The upper limit depends on the physical structure of the memory (i.e., the total number of cells). The first versions of MS-DOS were developed for the Intel 8088 CPU. Each register of this processor is designed to store a 16-bit number. That is, the 8088 CPU combines the contents of a segment register (say CS) with the contents of another register (say IP) to produce a 20-bit memory address, which limits the available memory to 2x20 bytes or 1 MB. Later, improved versions of MS-DOS appeared and, accordingly, improved CPU processors 80286 and 80386, allowing access to cells located beyond the boundaries of the first MB of memory. However, the 1 MB limit has not yet been overcome (at least in version 3.3), which is one of the main disadvantages of the operating system.

Memory access is organized by connecting the contents of one of the segment registers with the contents of one of the remaining registers. The value of the segment register is called the segment address. The value of the remaining registers in this case is called the relative address of the memory cell (from the beginning of the segment) or its short address. Thus, the byte address is calculated by multiplying the segment address by 16, and adding the short address to the resulting value.

Segment registers Segment registers are used to identify a memory segment. A segment is a contiguous block of memory, 64 K long. Segment registers are used in combination with a pointer register or index registers and in this case identify a specific memory cell.

There are four segment registers in total. The CS register is usually used to identify the memory block in which the program code is stored. The DS register identifies the memory area in which the data of this program is located. The SS register is used to organize access to the stack. (A stack is a temporarily distributed memory area that provides the “MS-DOS-application program” interface). Register ES - additional (or spare) segment register. It is assigned a variety of functions, some of which are discussed below.

Stack registers There are two stack registers. They are used in combination with the SS register and determine the location of the stack. The SP register is called the start of stack pointer, and in combination with the SS register identifies the first byte of the stack. The BP register is called the stack base pointer and, in combination with the SS register, identifies the last byte of the stack.

Index registers There are also two index registers. The SI and DI registers are used in combination with one of the segment registers and determine the location of a specific memory cell. The SI register is usually combined with the DS register, the DI register with the ES register.

General purpose registers General purpose registers include registers AX, BX, CX and DX (there are four of them). These are multifunctional registers.

The IP instruction pointer register is usually used in combination with the CS register and specifies the address of the next instruction.

Status flag register

The flags register usually contains nine processor status flags (each flag occupies 1 bit). These flags determine the result of specific operations performed under MS-DOS. Memory Registers A memory register contains 2 bytes of data (or 16 bits). In reality, general-purpose registers are single-byte. Thus, the AX register includes the AH register (which makes up the high byte of the AX register) and the AL register (which makes up the low byte of the AX register). Similarly, the BH, BL, CH, CL, DH and DL registers are single-byte.

MSDOS Drivers The two most important components of a computer's electronic hardware are its central processing unit (CPU) and its memory. The remaining components (disk drives, keyboard, displays, printers, etc.) are external to the computer. These external components of electronic equipment are called PERIPHERAL DEVICES or simply DEVICES.

The connection between the machine and the peripheral device is carried out in a strictly defined order. Each peripheral device in the operating system has a corresponding program that is responsible for its contact with the computer. These programs are called DRIVERS.

Application of drivers One of the main functions of the operating system is to provide a group of functional drivers available to system and application programs. If a running program needs contact with a peripheral device, it tells the operating system which device it needs, and MS-DOS provides it with the appropriate driver.

Character-by-character and block-by-block data transmission devices Character-by-character data transmission devices transmit information one character at a time. These devices include serial and parallel adapter ports and displays. In MS-DOS, each of these devices has a specific name (name). The MS-DOS driver can control only one character-by-character device. Block-by-block data transmission devices send information across blocks. Each block is typically 512 bytes. These devices include floppy disk drives, hard disk drives, and other storage devices. Block transfer devices do not have a specific name. The MS-DOS driver can serve several devices block by block

Interrupts An interrupt is a signal coming from software programs or generated by electronic equipment. An interrupt signal alerts the processor (CPU) to perform certain functions. For example, when you press any key, an interrupt signal is generated from the keyboard (i.e., from the electronic equipment), warning the processor about entering data from the keyboard.

Each type of interrupt corresponds to a specific serial number (a keyboard interrupt, for example, is designated number 9). Using this number, the processor distinguishes which handler needs to be called to process the interrupt signal. By convention, interrupt numbers are presented in hexadecimal format.

Interrupts numbered 20Н-2FH are reserved for system use. This means that application programs designed to interact with the system software can access these interrupts only in special cases that are defined by the operating system. Most often, the 21H interrupt is used programmatically - the function manager.

Function Manager Interrupt 21H is called “function manager”. The function manager is responsible for doing most of the work in MS-DOS. His responsibilities include providing access to system functions. Each function performs a specific task, such as opening a file, displaying a character string on the display screen, allocating a block of memory, or displaying the running version of MS-DOS. The functions are also differentiated by numbers.

To programmatically access a system function, you must do the following: (1) write the number of the corresponding function in the AN register; (2) write the parameters necessary for the function to operate in the appropriate registers; (3) cause interruption of 21H. When accessing interrupt 21H, control is transferred to MS-DOS. The operating system uses the value of the AH register to determine which function should be executed. Then the parameter values are read from the remaining (completely defined for each function) registers, after which the required function is executed. MS-DOS places the parameters returned by the function into the appropriate registers and returns control to the calling program. The program looks at the registers and analyzes the result of the function.

Reserved functions Some functions are marked as “reserved for system use.” These functions are used by the operating system, but IBM and Microsoft refuse to consider them in the official literature. Thanks to the efforts of programmers, the purpose of some of them became known. Users who use these functions often refer to them as “officially undocumented” rather than “reserved”.

Error code Many functions of MS-DOS versions set the current processor flag and return an error code in the AX register if an error occurred while calling the function. From special tables you can find out the cause of the error.

The concept of system, current and logical disks; DOS prompt.

Logical drive or volume (English volume) - part of the computer's long-term memory, considered as a whole for ease of use.

When DOS is ready to interact with the user, it displays invitation, for example A> or C:\>. This means that DOS is ready to receive commands. When the user is interacting with a program other than DOS, then there is no DOS prompt. However, most programs communicate with the user not using commands, but through menus, requests, pressing certain key combinations, etc. The DOS prompt usually contains information about the current directory. But sometimes it also includes information about the current time of day. The type of prompt can be changed using the DOS Prompt command.

The concept of the DOS kernel, the main functions of kernel modules;

The MS DOS kernel implements the MS DOS system, which is a special program supplied by Microsoft that includes a set of hardware-independent utility programs called system functions. These include: 1. File and record management. 2. Memory management. 3. Character-oriented input/output device. 4. Generation of other tasks. 5. Access to real time clock. The MS DOS kernel is read into memory during system initialization from the MSDOS.SYS file located on the boot disk; this file is distinguished by the hidden and system attributes.

Purpose of files config.sys And autoexec.bat;

The config.sys and autoexec.bat files play a major role in establishing the DOS configuration. When DOS boots, it reads the config.sys and autoexec.bat files from the root directory of the boot disk and executes the commands contained there. The config.sys file is a text file that contains special commands for setting up the DOS configuration: connecting various drivers, determining the size of the DOS system tables, etc. The commands specified in the config.sys file are executed during the DOS boot process.

When the config.sys file completes, the autoexec.bat command file is automatically executed if it exists in the root directory of the boot disk. As a rule, the autoexec.bat file contains commands for launching resident programs and other programs that are advisable to run every time DOS boots, as well as commands for setting DOS environment variables, specifying the list of directories in which programs to be launched are searched, and setting the DOS prompt format.

MS DOS- Microsoft disk operating system.

History of MS DOS

The history of MS DOS began back in 1980 at Seattle Computer Products.

Then it was called QDOS. The abbreviation stood for Quick and Dirty Operating System - a quick and dirty operating system.

Later it was renamed 86-DOS. This operating system replicated the API of another CP/M system. This was done because a lot of software was developed for CP/M..

The console commands were also taken from CP/M.

Microsoft, having received an order on November 6, 1980 from IBM to develop an operating system for new personal computers, bought 86-DOS for 50 thousand dollars and, after slightly modifying it, sold the license to IBM. Microsoft licensed IBM not only to ship DOS with new computers, but also to modify its source code.

This is how PC DOS appeared, but that's another story.

Thus, IBM began to distribute its personal computers with PC DOS and MS DOS operating systems.

But users preferred the version from Microsoft and so it began MS DOS era MS DOS files

The main components of MS DOS are 3 files:

Programming in MS DOS BIOS functions

Directly via I/O ports

Reliability of MS DOS

DOS does not restrict the programmer from using means of access to external devices. But the programmer pays for this freedom with reliability. A program in MS DOS takes over all control and if there is an error in the program that leads to memory corruption or incorrect access to equipment, it may freeze, execute garbage or

automatic reboot

computer.

MS DOS versions MS DOS 1.10, 1.11, 1.14 This version Microsoft company presented to IBM as part of an agreement to order system software for a personal computer. These versions were released in August 1981. Supported work with flexible

magnetic disks

with a diameter of 5.25 inches, a capacity of 160 kilobytes.

These discs were recorded on only one side.

These versions were full of errors, which prompted

IBM

discard the sources and release your own version of DOS - PC DOS. MS DOS 1.24 In March 1982, DOS learned to work with double-sided floppy disks. Their volume was already 320 kilobytes. At the same time, the FAT12 file system appeared. MS DOS 1.25 Initially, the functionality for working with double-sided discs was available only for computers assembled at IBM. Three months later, in version MS DOS 2.25, this functionality became available to other personal computer manufacturers. MS DOS 2.0 In March 1983, a revolutionary version of MS DOS was released. She already knew how to work with hard drives up to 10 megabytes in size.

It is now possible to distribute files into directories (folders). This version introduced the concept

file descriptor

- number identifying

open file

.

AT version of the MS DOS operating system. The system has been transformed with the release of a new version. In this version, it became possible to work with hard drives up to 20 MB in size, as well as dividing it into partitions. Of the special innovations - virtual disk in RAM.