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2. a presentation on2 3. DOS, short for "Disk Operating System", is anacronym for several closely related operatingsystems that dominated the IBM PC compatible market between 1981 and 1995.3 4. MS-DOS PC-DOS FreeDOS DR-DOS PTS-DOS ROM-DOS Caldera OpenDOS Novell DOS4 5. MS-DOS (or Microsoft Disk Operating System) is anoperating system for x86-based personal computers. Itwas the most commonly used member of the DOSfamily of operating systems, and was the mainoperating system for IBM PC compatible personal computers during the 1980s to the mid 1990s. It was gradually superseded by operating systems offering a graphical user interface (GUI), in particular by various generations of the Microsoft Windows operating system.5 6. All MS-DOS-type operating systems run on machineswith the Intel x86 or compatible CPUs, mainly the IBM PC and compatibles. Machine-dependent versions ofMS-DOS were produced for many non-IBM-compatible x86-based machines, with variations from relabeling ofthe Microsoft distribution under the manufacturers name,to versions specifically designed to work with non-IBM-PC-compatible hardware. DOS-Cs predecessor DOS/NT ran on Motorola 68000 CPUs.6 7. MS-DOS grew from a 1981 request by IBM for an operating system for its IBM PC range of personalcomputers. Microsoft bought the rights to QDOS(Quick and Dirty Operating System), also known as 86-DOS, from Seattle Computer Products, and began work on modifying it to meet IBMs specification. The first edition, MS-DOS 1.0, waslaunched in 1982. The version shipped with IBMs PCs was called PC DOS. 7 8. CharacterUser Interface (or Commandline User Interface) Single User Single Tasking Case independent commands8 9. 9 10. P.O.S.T Bootstrap LoaderLoads OS from disk IO.SYSMSDOS.SYSCOMMAND.COMCONFIG.SYS AUTOEXEC.BAT 10 11. IO.SYS is an essential part of MS-DOS andWindows 9x. It contains the default MS-DOSdevice drivers and the DOS initializationprogram.11 12. MSDOS.SYS an important system file onMS-DOS and Windows 9x systems. It is runafter IO.SYS. In MS-DOS, it contains the core operating system code, the kernel. By default, the file is located in the root directory of the bootable drive/partition (normally C:)and has the hidden, read-only, and system file attributes set.12 13. COMMAND.COM is the filename of thedefault operating system shell for DOS operating systems and It has an additional role as the first program run after boot, hence being responsible for setting up the system by running the AUTOEXEC.BATconfiguration file, and being the ancestor of all processes. 13 14. CONFIG.SYS is the primary configuration file for the DOS operating system. It is a special file that contains setup or configuration instructions for the computer system. In DOS,CONFIG.SYS is located in the root directory of the drive from which DOS was booted. 14 15. AUTOEXEC.BAT is a system file foundoriginally on DOS-type operating systems. It isa plain-text batch file that is located in the root directory of the boot device. The name of thefile stands for "automatic execution", which describes its function in automaticallyexecuting commands on system startup.15 16. DOS InternalCommands ExternalCommands16 17. Internal commands are stored in theCOMMAND.COM file and these are loaded inthe system memory all the time. These commands are embedded into MS-DOS andwill run as long as DOS is running, without the need for any external files.17 18. These commands are stored in separate fileslocated in the secondary storage (HDD, FDD,etc). These are small utility programs thatperform specific functions in DOS. These commands are not loaded in system memory all the time and will not work if the storagedevice where the files are located is notfound. 18 19. Cls(Clear screen): Clears all text on screen Md(Make Directory): Creates a newfolder/directory Cd (Change Directory): Switches directory Cd.. : Switches to previous parent directory Cd : Switches to root directory Copy : Copies one or more files to analternate location Dir : Displays a list of the available files in adirectory Del (Delete): Used to delete one or more files19 20. Attrib (Attributes): Setschanges file attributes Chkdsk (Check Disk): Checks the hard drive(s) for errors andfixes them if necessary Fdisk : Deletes and creates partitions on the hard disk drive Format : Used to erase information off of a computer disketteor fixed drive. Help : Used to access the information and help file from a MS-DOS prompt Label : used to view or change the label of the computer diskdrives Tree : Displays the filefolder hierarchy of a directory in aneasy to read, graphical form. Deltree : Used to delete files and entire directories from thecomputer. 20 21. Nosupport for multi-tasking No multi-user support By default it can only access 640 KB ofRAM Does not support hard drives larger than8.4 GB or partitions larger than 2 GB No memory protection No Graphical User Interface (GUI) File names limited to 8 characters and fileextensions to 3 characters only21 22. Today, MS-DOS is rarely used for desktop computing. Since the release of Windows 95, it was integrated as a full product used for bootstrappingand troubleshooting, and no longer released as astandalone product. the only versions of DOS currently recognized as stand-alone OSs, and supported as such by the Microsoft Corporation areDOS 6.0 and 6.22, both of which remain available fordownload via their MSDN. 22 23. Microsoft Windows 95 Microsoft Windows 98 Microsoft Windows ME 23 24. All versions of Microsoft Windows have had an MS-DOS like command-line interface(CLI). This could run many DOS command line utilities in the same command-linesession, allowing piping between commands. The user interface, and the icon up to Windows 2000, followed the native MS-DOSinterface. 24 25. Consumer Windows (up to 3.11, Win9x, WinME) ran as a Graphical User Interface (GUI) running on top of MS-DOS.True 32-bit versions of Windows, starting with NT and including 2000, XP, and Vista, are not based upon DOS. These include theNT Virtual DOS Machine (NTVDM), which runs a modified version of MS-DOS 5 in a virtual machine. While DOS-based versions used the traditional COMMAND.COM for a command lineinterface, MS-Windows NT and its derivatives use cmd.exe, a descendant of OS/2s command interpreter which recognizes many DOS commands25 26. Windows XP x64, Windows Vista x64 andWindows 7 x64 editions do not contain the NTVDM (because the x86-64 architecture doesnot allow it) and therefore they cannot run 16-bit DOS applications directly. COMMAND.COM is missing and the only way to run a DOS application under these versions of Windows is by using an emulator. 26 27. 27 28. 28 29. 29 30. 30