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Lesson 2-DOS

Lesson 2-DOS. Overview. Introduction to DOS. Installing DOS. The file allocation table (FAT) file system. The DOS command prompt. Overview. Understanding the DOS boot-up process and startup disks. Working with DOS in Windows. Troubleshooting common DOS problems. Introduction to DOS.

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Lesson 2-DOS

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  1. Lesson 2-DOS

  2. Overview • Introduction to DOS. • Installing DOS. • The file allocation table (FAT) file system. • The DOS command prompt.

  3. Overview • Understanding the DOS boot-up process and startup disks. • Working with DOS in Windows. • Troubleshooting common DOS problems.

  4. Introduction to DOS • Versions of DOS. • DOS strengths. • DOS weaknesses.

  5. Versions of DOS • Different versions of DOS exist, most of which have been introduced by Microsoft. • Microsoft created PC DOS for IBM, and later licensed DOS as MS-DOS to other manufacturers. • DOS 5.0 was the first version to be available as a separate product from Microsoft.

  6. Versions of DOS • PC DOS can be installed on Microsoft/Intel compatible computers as well as IBM computers. • Digital Research created a DOS product called DR-DOS in the 1980’s. • FreeDOS is a DOS version that is distributed without charge for the software under the GNU GPL license. • FreeDOS is designed to be 100 percent compatible with MS-DOS.

  7. DOS Strengths • DOS works with applications written specifically for DOS. • DOS is used on some systems to provide backward compatibility with the legacy application. • DOS utilizes a very small amount of memory.

  8. DOS Strengths • DOS is more compact than the Windows operating system and hence is useful for embedded systems or for portability. • DOS is popular as an operating system due to its ability to pack all startup files on a single diskette. • The diskette is also known as the startup disk.

  9. DOS Strengths • The startup disk can be used for booting up a computer and running special diagnostic programs. • The DOS startup diskette also accommodates additional files, such as drivers and utilities.

  10. DOS Weaknesses • Processor mode limits. • Memory limits. • Multitasking limits. • Hard drive limits.

  11. Processor Mode Limits • DOS was written for Intel 8088 processors that only supported the real mode of operation. • Newer Intel processors beginning with 386DX support both the real and the protected modes of operation. • However, the newer Intel processors still start in the real mode, and the operating system switches the processor from the real mode to the protected mode.

  12. Memory Limits • Intel processors in the real mode can use only 1 MB of memory address. • The first 640 KB of RAM, also known as the conventional memory, is used as a workspace for the operating system and the application programs and data. • The remaining 384 KB of address is reserved for system BIOS and various adapters and network cards.

  13. Multitasking Limits • DOS can only run one application program at a time, which is referred to as single tasking. • DOS does not support the advanced multitasking capabilities of the protected mode in advanced Intel processors.

  14. Hard Drive Limits • DOS can only support hard drives up to 7.8 GB. • DOS can use only logical drives that are 2 GB or less and within the 7.8 GB total disk space limit. • A logical drive is a portion of the physical hard drive with a letter assigned to it.

  15. Installing DOS • DOS hardware requirements. • Installing DOS on a hard disk.

  16. DOS Hardware Requirements The general DOS hardware requirements for MS-DOS 6.22 and IBM PC-DOS are: • An IBM or a compatible personal computer. • 6 MB of free hard disk space. • 512 KB of memory.

  17. Installing DOS on a Hard Disk • To install DOS on a hard disk, it is essential that the computer is a complete system with all the necessary connections and the minimal components installed. • The MS-DOS 6.22 Setup program prepares the hard disk for installation by creating a partition and formatting it.

  18. Installing DOS on a Hard Disk • A partition is an area of a physical hard disk that defines the space that will be used for the logical drives. • A Microsoft/Intel standard PC, an un-partitioned hard drive, and three DOS 6.22 setup diskettes are required for installing DOS on a hard disk. • The setup copies all the MS-DOS files to the default location C:\DOS.

  19. The FAT File System • Using files and directories in DOS. • DOS file attributes.

  20. Using Files and Directories in DOS • The FAT and the root directory are the two primary components of the FAT file system. • DOS uses the FAT component to remember the location of a file on the disk. • A directory is a place where DOS stores information about files, including a reference to the FAT table.

  21. Using Files and Directories in DOS FAT table: • The FAT table is a table in which DOS records how disk space has been used. • DOS divides the entire disk space for one volume into equal-sized allocation units called clusters. • A cluster is the minimum space that can be given to a file. • The FAT table has a single entry for each cluster.

  22. Using Files and Directories in DOS Directory: • A directory is a special file that contains a list of files and other directories. • The root directory is the top-level directory.

  23. Using Files and Directories in DOS Directory (continued): • A directory that contains other directories is called a ‘parent’ directory, and a directory inside the parent directory is called a ‘child’ directory. • Each directory entry in DOS contains the name of a file or directory, the time and date of its creation or modification, its size, attributes, and beginning cluster information.

  24. Using Files and Directories in DOS Using the Directory and the FAT to find a file

  25. Using Files and Directories in DOS DOS file-naming rules: • DOS can have a file name of up to eight characters, followed by a period, and an extension of up to three characters. • A filename can include alphanumeric characters and a few special characters. It cannot include spaces. • DOS also uses the wildcard characters asterisk (*) and question mark (?) to locate files and folders.

  26. Using Files and Directories in DOS DOS file types: • bak, bas, bat, com, dos, exe, sys, and txt are some common file extensions and file types recognized by DOS. • com, exe, and bat are the three types of files that can be executed by DOS.

  27. DOS File Attributes • File attributes determine the manner in which DOS handles files. • Read-only, archive, system, hidden, volume label, and directory are DOS file attributes. • The ATTRIB command can be used to view and modify some of the attributes.

  28. The DOS Command Prompt • DOS commands. • Managing files and directories.

  29. DOS Commands • Syntax is a set of rules for correctly entering a specific command at the command line. • Syntax includes the command name and the parameters that act as instructions to the command. • The HELP command can be used to find the syntax for a command.

  30. DOS Commands • The command interpreter, COMMAND.COM, interprets the command entered at the prompt. • The command interpreter receives commands, finds the actual program code for the command and loads it into the memory, and issues additional instructions to the command, if any.

  31. DOS Commands • The command interpreter parses the command entry based on special delimiter characters. • The DOS command interpreter then loads the command named at the beginning of the command line.

  32. Managing Files and Directories • File management in DOS is centered on the abilities and limits of the FAT file system. • It is essential to design a directory structure to save and organize files.

  33. Managing Files and Directories • The directory/folder structure in DOS is hierarchical. • The hierarchy is Drive |Directory |File Name. • The TREE command can be used to view the entire directory structure.

  34. Managing Files and Directories • The MD (Make Directory) command is used to create a directory. • The CD or CHDIR command is used for moving between directories. • The RD (Remove Directory) command is used to delete an empty directory.

  35. Managing Files and Directories File management commands: • DOS commands are divided into internal commands and external commands. • Internal commands are loaded into the memory along with DOS.

  36. Managing Files and Directories File management commands (continued): • DIR (Directory), MD, CD, CLS (CLear Screen), COPY, REN (REName), RD, and TYPE are some of the internal commands. • XCOPY, DISKCOPY, and DELTREE are the external commands used often.

  37. DOS Command Function DIR Displays a list of files and folders. DIR /? Lists the available syntax for the DIR command. DIR /P List data one page at a time. CD .. Moves to the parent directory from the present directory. CLS Clears the screen. VER Displays the MS-DOS version. XCOPY Used to copy files and entire directories. COPY Used to copy only files. DELTREE Used to delete an entire directory and its contents. Managing Files and Directories DOS commands and their functionality

  38. Understanding the DOS Boot-Up Process and Startup Disks • Personal computers are multi-purpose devices. • Understanding the normal startup process of the system helps troubleshoot problems that occur during boot-up.

  39. Understanding the DOS Boot-Up Process and Startup Disks • DOS system files. • The DOS boot-up process. • Creating a DOS startup disk.

  40. DOS System Files • IO.SYS, MSDOS.SYS, and COMMAND.COM are the three critical system files in MS-DOS. • The system files are read-only, and must be present on the root drive to start DOS either from the hard disk or a floppy disk. • DOS also uses the CONFIG.SYS and AUTOEXEC.BAT text files during boot-up.

  41. DOS System Files CONFIG.SYS and AUTOEXEC.BAT: • The CONFIG.SYS file is used to add device drivers to DOS and to modify DOS settings. • BUFFERS, DOS, FILES, STACKS, DEVICE, and DEVICEHIGH are some of the most common CONFIG.SYS commands.

  42. DOS System Files CONFIG.SYS and AUTOEXEC.BAT (continued): • The DEVICE and DEVICEHIGH commands are used to load device drivers. • AUTOEXEC.BAT is a text file containing commands that can be executed by the command processor.

  43. The DOS Boot-Up Process A PC can be booted up by: • Turning on the power switch of the PC. This is also known as cold boot. • Using the Ctrl-Alt-Delete key combination to reboot the system. This procedure is also known as warm boot.

  44. The DOS Boot-Up Process • Once powered on, the processor loads a special ROM-based program, called Power-On Self-Test (POST), into the memory. • POST runs a series of small diagnostic tests on the hardware, and transfers the control to the bootstrap loader. • The bootstrap loader is a small program in the ROM BIOS.

  45. The DOS Boot-Up Process • The ROM BIOS bootstrap loader loads the boot sector from the disk into the memory, which, in turn, runs the operating system loading program. • In situations where the operating system is loaded on the hard drive, the bootstrap loader looks into the MBR (master boot record) and reads the partition table for the primary partition.

  46. Creating a DOS Startup Disk • Using FORMAT to create a startup disk. • Using SYS to create a startup disk. • Using Windows to create a startup disk.

  47. Using FORMAT to Create a StartupDisk • The FORMAT command prepares the diskette and places a new root directory and FAT on the disk. • The /S switch option is used with the FORMAT command to place the system files on the diskette.

  48. Using SYS to Create a Startup Disk • The SYS command places the DOS system files on a previously formatted diskette. • The SYS.COM program is used to create a startup disk.

  49. Using Windows to Create a Startup Disk • Windows 95 and 98 use the Startup Disk option for creating a startup disk. • Windows XP uses the My Computer or Windows Explorer option to create a MS-DOS startup disk.

  50. Working with DOS in Windows • Running DOS applications in Windows. • Using the command prompt in Windows.

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