Lesson 2-DOS

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 1980s.
• 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
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.

51
Running DOS Applications in Windows

• A DOS application runs in a virtual machine while
  running in Windows.
• The NTVDM.EXE is the primary software component
  for creating a virtual DOS machine.
• DOS applications running in Windows require
  memory as well as a lot of processor cycles.

52
Running DOS Applications in Windows

• DOS applications running in Windows rely on a
  special file called a program information file
  (PIF).
• The PIF provides the operating system with
  information on how to configure the virtual
  machine with the memory and other options for the
  application.
• Windows comes with one Windows application and
  one DOS application.

53
Using the Command Prompt in Windows

• All versions of Windows allow the user to work at
  the command prompt while the operating system is
  running.
• The command prompt in Windows 95 and 98 runs in a
  DOS virtual machine.

54
Using the Command Prompt in Windows

• In Windows NT, Windows 2000, and Windows XP the
  CMD.EXE program is launched when the command
  prompt option is selected.
• The CMD.EXE offers a full 32-bit, character-mode
  command prompt.

55
Troubleshooting Common DOS Problems

• Non-System Disk error message
• A Non-System Disk error message indicates that
  the operating system loader program is unable to
  locate the IO.SYS, or MSDOS.SYS, or both.
• The problem can be rectified by ensuring that the
  operating system is booted from the disk that
  holds the operating system.

56
Troubleshooting Common DOS Problems

• Bad or Missing Command Interpreter error
  message
• The Bad or Missing Command Interpreter error
  message implies that the file COMMAND.COM is
  missing or that the version is different than
  IO.SYS and MSDOS.SYS.
• The error can be rectified by copying the
  COMMAND.COM file with the correct date and time
  from the floppy disk to the hard disk.

57
Troubleshooting Common DOS Problems

• Bad Command or File Name error message
• The Bad Command or File Name error message
  implies that the command name or the file name
  (or a directory name) in one of the parameters is
  incorrect.
• The error can be rectified by identifying typos
  and re-entering the command correctly.

58
Summary

• DOS is a single-tasking operating system.
• DOS uses the FAT16 file system, and only uses
  conventional memory.
• The FAT file system uses the 8.3 naming
  convention for files and directories.

59
Summary

• DOS commands may be internal or external.
• It is important to understand the boot-up process
  of an operating system in order to troubleshoot
  boot-up failures.
• The FORMAT or SYS commands and the Windows
  Startup Disk option can be used for creating a
  DOS startup disk.