mcgraw-hill/irwin© 2006 the mcgraw-hill companies, inc. all rights reserved. 2-1
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2-1McGraw-Hill/Irwin © 2006 The McGraw-Hill Companies, Inc. All rights reserved.
Disk Operating System (DOS)
Finding DOS and Understanding its Strengths and Weaknesses
Installing DOSHow the FAT File System Works
Working with the DOS Command PromptUnderstanding the DOS Bootup ProcessTroubleshooting Common DOS Problems
Chapter
2
2-3McGraw-Hill/Irwin © 2006 The McGraw-Hill Companies, Inc. All rights reserved.
Learning Objectives
•Measure the value, strengths, and weaknesses
of DOS • Install DOS •Use the FAT file system •Use DOS commands for file management and
other tasks •Describe the DOS bootup process and create
startup disks •Troubleshoot common DOS problems
2-4McGraw-Hill/Irwin © 2006 The McGraw-Hill Companies, Inc. All rights reserved.
Finding DOS and Understanding its Strengths and Weaknesses
•Versions of DOS• CP/M was an important predecessor to DOS• Many versions of DOS, several introduced
by Microsoft (MS)• MS created PC DOS for IBM• Later licensed DOS as MS-DOS to other
manufacturers• MS-DOS 5.0 first version available as a separate
product
2-5McGraw-Hill/Irwin © 2006 The McGraw-Hill Companies, Inc. All rights reserved.
Finding DOS and Understanding its Strengths and Weaknesses
•Versions of DOS (continued) • PC DOS now works on Microsoft/Intel
compatible computers• Digital Research (of CP/M fame) introduced
DR-DOS in 1987• DR-DOS 8.0 introduced in 2004 by DeviceLogics• FreeDOS distributed without charge under
GNU GPL license
2-6McGraw-Hill/Irwin © 2006 The McGraw-Hill Companies, Inc. All rights reserved.
Finding DOS and Understanding its Strengths and Weaknesses
•DOS’ Strengths• DOS for backward compatibility with DOS apps• DOS when you need a small OS• DOS is more compact than Windows and hence
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 floppy disk
2-7McGraw-Hill/Irwin © 2006 The McGraw-Hill Companies, Inc. All rights reserved.
Finding DOS and Understanding its Strengths and Weaknesses
•DOS Strengths (continued)
• The floppy disk is also known as the startup disk
• Startup disk accommodates additional files, such as drivers and utilities
• Startup disk can be used for booting up a computer and running special diagnostic programs
2-8McGraw-Hill/Irwin © 2006 The McGraw-Hill Companies, Inc. All rights reserved.
Finding DOS and Understanding its Strengths and Weaknesses
•DOS Weaknesses • Processor mode limits• Memory limits• Multitasking limits• Hard drive limits
2-9McGraw-Hill/Irwin © 2006 The McGraw-Hill Companies, Inc. All rights reserved.
Finding DOS and Understanding its Strengths and Weaknesses
• DOS Weaknesses (continued) • Processor Mode Limits
• Only supports real mode of operation of Intel processors
• Newer Intel processors start in the real mode, and newer OSs (Windows, Linux, UNIX) switch the processor from the real mode to the protected mode
• Memory Limits • Intel processors in real mode use only 1 MB• 640 KB of RAM (conventional memory) is workspace
for the OS, applications and data• 384 KB of addresses reserved for system BIOS and
RAM and ROM on adapters
2-10McGraw-Hill/Irwin © 2006 The McGraw-Hill Companies, Inc. All rights reserved.
Finding DOS and Understanding its Strengths and Weaknesses
•DOS Weaknesses (continued)
• Multitasking Limits • DOS is a single-tasking OS
• Hard Drive Limits • DOS only supports hard drives up to 7.8 GB• DOS uses 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
2-11McGraw-Hill/Irwin © 2006 The McGraw-Hill Companies, Inc. All rights reserved.
Installing DOS
•DOS Hardware Requirements • The general DOS hardware requirements for
MS-DOS 6.22 and IBM PC-DOS • An IBM or compatible personal computer• 6MB of free hard disk space for the DOS utilities• 512KB of memory
2-12McGraw-Hill/Irwin © 2006 The McGraw-Hill Companies, Inc. All rights reserved.
Installing DOS
•Preparing for DOS Installation• Assure that the computer is a complete
system with all the necessary components
• Setup program partitions and formats the hard disk
• Partition: an area of a physical hard disk that contains one or more logical drives
2-13McGraw-Hill/Irwin © 2006 The McGraw-Hill Companies, Inc. All rights reserved.
Installing DOS
•Partitioning a Hard Disk in MS-DOS• Physical format is done at the factory • Master Boot Record (MBR), the 1st sector
on disk, contains the partition table• Partitioning is the first step to prepare a
hard disk• Each partition needs a logical format within
each logical drive• Partitioning and formatting included in OS
installation
2-14McGraw-Hill/Irwin © 2006 The McGraw-Hill Companies, Inc. All rights reserved.
Installing DOS
•Partitioning a Hard Disk in MS-DOS (continued)
• FDISK – the partitioning program of MS-DOS• Primary partition has only one logical drive• 2GB is maximum primary partition size in
MS-DOS• Extended partition contains one or more
logical drives• After partitioning, then format logical drives
2-15McGraw-Hill/Irwin © 2006 The McGraw-Hill Companies, Inc. All rights reserved.
Installing DOS
Step-by-Step 2.01
Installing DOS on a Hard Disk
Page 55
2-16McGraw-Hill/Irwin © 2006 The McGraw-Hill Companies, Inc. All rights reserved.
How the FAT File System Works
•FAT File System Components• FAT Table
• File allocation table (FAT) – DOS records disk space usage
• Cluster – minimum space allocated to a file
2-17McGraw-Hill/Irwin © 2006 The McGraw-Hill Companies, Inc. All rights reserved.
How the FAT File System Works
•FAT File System Components (continued)
• FAT12, FAT16, and FAT32• FAT16 – used on hard disks• FAT32 – available since Windows 95 OEM SR2• FAT12 – used on floppy disksThe number refers to the size of each entry in the
FAT table. Length of entry limits the number of entries the FAT table can hold.
2-18McGraw-Hill/Irwin © 2006 The McGraw-Hill Companies, Inc. All rights reserved.
How the FAT File System Works
•FAT File System Components (continued)
• How Cluster Size Affects Partitions • FAT16 file system limited to 65,525 clusters• Maximum cluster size 32,768 bytes (32K)• 65,525 x 32,768 = 2GB (maximum partition size
supported by the FAT16 file system)
2-19McGraw-Hill/Irwin © 2006 The McGraw-Hill Companies, Inc. All rights reserved.
How the FAT File System Works
•FAT File System Components (continued)
• Root Directory and Other Directories • The FAT and the root directory are the two
primary components of the FAT file system• DOS uses the FAT to record the location of a
file on the disk• A directory is a place where DOS stores
information about files, including a referenceto the FAT table
• Root directory is the top level directory
2-20McGraw-Hill/Irwin © 2006 The McGraw-Hill Companies, Inc. All rights reserved.
How the FAT File System Works
•FAT File System Components (continued)
• Root Directory and Other Directories (continued)
• Parent directory contains other directories• Child directory (subdirectory) is within a parent• Each directory entry contains the name of a file
or directory, the time and date of its creation or modification, its size, attributes, and beginning cluster information
2-21McGraw-Hill/Irwin © 2006 The McGraw-Hill Companies, Inc. All rights reserved.
How the FAT File System Works
•Using a Directory and the FAT Table to find a File• Directory is like a phone directory for DOS• Finds file name and listing in the directory• Reads the starting cluster number in directory• Looks in the FAT table (like a map of city) for
location on disk
2-22McGraw-Hill/Irwin © 2006 The McGraw-Hill Companies, Inc. All rights reserved.
How the FAT File System Works
•DOS file-naming rules:• A file name is up to eight characters, followed
by a period, and an extension of up to three characters
• A file name and extension can include alpha-numeric characters and a few special characters, but no spaces
• Use the wildcard characters asterisk (*) and question mark (?) to locate files and folders
2-23McGraw-Hill/Irwin © 2006 The McGraw-Hill Companies, Inc. All rights reserved.
How the FAT File System Works
•DOS File Types• BAK, BAS, BAT, COM, DOS, EXE, SYS, and TXT
are some common file extensions and file types recognized by DOS
•Executable Files • COM, EXE, and BAT are the three types of files
that can be executed by DOS
2-24McGraw-Hill/Irwin © 2006 The McGraw-Hill Companies, Inc. All rights reserved.
How the FAT File System Works
Step-by-Step 2.02
Creating a Simple Batch File
Page 63
2-25McGraw-Hill/Irwin © 2006 The McGraw-Hill Companies, Inc. All rights reserved.
How the FAT File System Works
• Read-only• Archive • System
• Hidden• Volume
label• Directory
•DOS File Attributes
•Determine the manner in which DOS handles files
2-26McGraw-Hill/Irwin © 2006 The McGraw-Hill Companies, Inc. All rights reserved.
How the FAT File System Works
•LABEL command• Creates or changes a volume label (name)• If a volume has a label, FORMAT requires
the name before reformatting
2-27McGraw-Hill/Irwin © 2006 The McGraw-Hill Companies, Inc. All rights reserved.
How the FAT File System Works
•ATTRIB command• Displays and modifies attributes • Works on read-only, archive, system, and
hidden files• Works in both MS-DOS and Windows on
FAT and NTFS
2-28McGraw-Hill/Irwin © 2006 The McGraw-Hill Companies, Inc. All rights reserved.
Working with the DOS Command Prompt
•Success at the DOS Prompt• Success means correctly entering commands
and getting desired results• Important for working with DOS and other OSs
2-29McGraw-Hill/Irwin © 2006 The McGraw-Hill Companies, Inc. All rights reserved.
Working with the DOS Command Prompt
Step-by-Step 2.03
Using the Online Help in DOS
Page 68
2-30McGraw-Hill/Irwin © 2006 The McGraw-Hill Companies, Inc. All rights reserved.
Working with the DOS Command Prompt
•Success at the DOS Prompt (continued)
• What is the Correct Syntax?• Syntax is a set of rules for correctly entering a
specific command at the command line• The HELP command can be used to find the
syntax for a command• COMMAND /?
2-31McGraw-Hill/Irwin © 2006 The McGraw-Hill Companies, Inc. All rights reserved.
Working with the DOS Command Prompt
•Success at the DOS Prompt (continued)• How is a Command Interpreted?
• COMMAND.COM interprets the command entered at the prompt
• COMMAND.COM loads each command into the memory, and issues additional instructions to the command
• COMMAND.COM parses the command entry based on special delimiter characters
2-32McGraw-Hill/Irwin © 2006 The McGraw-Hill Companies, Inc. All rights reserved.
Working with the DOS Command Prompt
•How is a Program Found and Loaded?• COMMAND.COM loads the command named
at the beginning of the command line• Must find the actual program code
• First checks its own list of internal commands
• Then looks for an external command in the current directory, and then in a list called the search path
2-33McGraw-Hill/Irwin © 2006 The McGraw-Hill Companies, Inc. All rights reserved.
Working with the DOS Command Prompt
•Learning to Manage 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
2-34McGraw-Hill/Irwin © 2006 The McGraw-Hill Companies, Inc. All rights reserved.
Working with the DOS Command Prompt
•Learning to Manage Files and Directories (continued)
• Designing a Directory Structure for File Management• DOS directory/folder structure is hierarchical• Drive | Directory | File Name• TREE command can be used to view the entire
directory structure• Store data in a separate directory from
applications
2-35McGraw-Hill/Irwin © 2006 The McGraw-Hill Companies, Inc. All rights reserved.
Working with the DOS Command Prompt
•Learning to Manage Files and Directories (continued)
• Creating and Removing Directories• MD (Make Directory) will create a directory• CD or CHDIR (Change Directory) allows
movement between directories• RD (Remove Directory) deletes an empty
directory
2-36McGraw-Hill/Irwin © 2006 The McGraw-Hill Companies, Inc. All rights reserved.
Working with the DOS Command Prompt
•Learning to Manage Files and Directories (continued)
• Use File Management Commands• DOS commands are divided into internal
commands and external commands• Internal commands are loaded into the memory
along with DOS
2-37McGraw-Hill/Irwin © 2006 The McGraw-Hill Companies, Inc. All rights reserved.
Working with the DOS Command Prompt
•Learning to Manage Files and Directories (continued)
• Use 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 often-used external commands
2-38McGraw-Hill/Irwin © 2006 The McGraw-Hill Companies, Inc. All rights reserved.
Working with the DOS Command Prompt
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.
DOS commands and their
functionality
2-39McGraw-Hill/Irwin © 2006 The McGraw-Hill Companies, Inc. All rights reserved.
Working with the DOS Command Prompt
Step-by-Step 2.04
Managing Files and Directories
Page 73
2-40McGraw-Hill/Irwin © 2006 The McGraw-Hill Companies, Inc. All rights reserved.
Understanding the DOS Boot-Up Process and Startup Disks
•Why You Should Learn the DOS Bootup Process• Personal computers are multi-purpose devices.• Understanding the normal startup process of
the system helps troubleshoot problems that occur during boot-up.
2-41McGraw-Hill/Irwin © 2006 The McGraw-Hill Companies, Inc. All rights reserved.
Understanding the DOS Boot-Up Process and Startup Disks
•DOS system files• IO.SYS handles hardware interaction and
loading of drivers
• MSDOS.SYS is the kernel of DOS• COMMAND.COM is the command interpreter
2-42McGraw-Hill/Irwin © 2006 The McGraw-Hill Companies, Inc. All rights reserved.
Understanding the DOS Boot-Up Process and Startup Disks
•DOS system files (continued)
• DOS Configuration Files• CONFIG.SYS – adds device drivers and modifies
DOS settingsBUFFERS DOSDEVICE FILESDEVICEHIGH STACKS
• AUTOEXEC.BAT batch file loaded during bootupPATH PROMPT SET
2-43McGraw-Hill/Irwin © 2006 The McGraw-Hill Companies, Inc. All rights reserved.
Understanding the DOS Boot-Up Process and Startup Disks
•The DOS Bootup Process• A PC can be booted up by:
• Turning on the power switch of the PC (a cold boot)
• Using the Ctrl-Alt-Delete key combination to reboot the system (a warm boot)
2-44McGraw-Hill/Irwin © 2006 The McGraw-Hill Companies, Inc. All rights reserved.
Understanding the DOS Boot-Up Process and Startup Disks
•The DOS Bootup Process (continued)
• The processor loads a special ROM-based program, called Power-On Self-Test (POST)
• POST runs a series of small diagnostic tests on the hardware, and loads the bootstrap loader
• The bootstrap loader is a small program in the
ROM BIOS
2-45McGraw-Hill/Irwin © 2006 The McGraw-Hill Companies, Inc. All rights reserved.
Understanding the DOS Boot-Up Process and Startup Disks
•The DOS Bootup Process (continued)
• On a hard drive, the bootstrap loader looks into the MBR (master boot record) and reads the partition table for the primary active partition
• The bootstrap loader loads the boot sector from the logical drive, which, in turn, runs the operating system loading program
2-46McGraw-Hill/Irwin © 2006 The McGraw-Hill Companies, Inc. All rights reserved.
Understanding the DOS Boot-Up Process and Startup Disks
•Creating a DOS Startup Floppy Disk• Using FORMAT to create a startup disk• Using SYS to create a startup disk• Using Windows to create a startup disk
2-47McGraw-Hill/Irwin © 2006 The McGraw-Hill Companies, Inc. All rights reserved.
Understanding the DOS Boot-Up Process and Startup Disks
•Using FORMAT to Create a Startup Disk• The FORMAT command prepares the diskette
and places a new root directory and FAT on the disk
• The /S switch option places the system files on the diskette
2-48McGraw-Hill/Irwin © 2006 The McGraw-Hill Companies, Inc. All rights reserved.
Understanding the DOS Boot-Up Process and Startup Disks
Step-by-Step 2.05
Create a Startup Floppy Disk Using FORMAT
Page 83
2-49McGraw-Hill/Irwin © 2006 The McGraw-Hill Companies, Inc. All rights reserved.
Understanding the DOS Boot-Up Process and Startup Disks
•Using SYS to Create a Startup Disk• The SYS command places the DOS system files
on a previously formatted floppy disk• To put the DOS system files on a floppy disk
enter sys a:
2-50McGraw-Hill/Irwin © 2006 The McGraw-Hill Companies, Inc. All rights reserved.
Understanding the DOS Boot-Up Process and Startup Disks
•Using Windows to Create a Startup Disk• In Windows 95 and 98 go to Control Panel |
Add/Remove Programs | Startup Disk• In Windows XP format a disk from within My
Computer or Windows Explorer and select the option to create a MS-DOS startup disk
2-51McGraw-Hill/Irwin © 2006 The McGraw-Hill Companies, Inc. All rights reserved.
Troubleshooting Common DOS
Problems •“Non-System Disk” error message
• The OS loader program (boot sector) is unable
to locate the IO.SYS, or MSDOS.SYS, or both• Rectify by ensuring that the OS is booted
from the disk that holds the OS
2-52McGraw-Hill/Irwin © 2006 The McGraw-Hill Companies, Inc. All rights reserved.
•“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
• Rectify by copying the COMMAND.COM file with the correct date and time from the floppy disk to the hard disk
Troubleshooting Common DOS
Problems
2-53McGraw-Hill/Irwin © 2006 The McGraw-Hill Companies, Inc. All rights reserved.
•“Bad Command or File Name” error message• Implies that the command name or the file
name (or a directory name) used in the command line
is incorrect• Rectify by identifying typos and re-entering the
command correctly
Troubleshooting Common DOS
Problems
2-54McGraw-Hill/Irwin © 2006 The McGraw-Hill Companies, Inc. All rights reserved.
Troubleshooting Common DOS
Problems•A request to enter the current date and time
• Means that DOS did not find an AUTOEXEC.BAT file
• If you previously had one, investigate why and how you don’t now
2-55McGraw-Hill/Irwin © 2006 The McGraw-Hill Companies, Inc. All rights reserved.
Chapter Summary
Finding DOS and Understanding Its Strengths and Weaknesses• One reason DOS is still in limited use today is its
small size, which makes it a choice for embedded systems
• Another reason is that its system files easily fit on a floppy disk, leaving room for other small programs
• Technicians can run diagnostic utilities from a DOS floppy disk
2-56McGraw-Hill/Irwin © 2006 The McGraw-Hill Companies, Inc. All rights reserved.
Chapter Summary
Finding DOS and Understanding Its Strengths and Weaknesses• Windows can run DOS in a virtual DOS machine• Some applications run too slowly or not at all
in a virtual machine, so they must be run on a computer running DOS
• DOS can only access real-mode of the Intel processors
• DOS is a single-tasking operating system• DOS provides limited services for DOS
applications
2-57McGraw-Hill/Irwin © 2006 The McGraw-Hill Companies, Inc. All rights reserved.
Chapter Summary
Finding DOS and Understanding Its Strengths and Weaknesses• DOS applications can only use conventional
memory• Microsoft no longer supports or sells MS-DOS• IBM sells PC DOS 2000• Digital Research sold DR-DOS to Novell • DR-DOS is now sold through DeviceLogics• Versions of DOS can be found for free on the
Internet
2-58McGraw-Hill/Irwin © 2006 The McGraw-Hill Companies, Inc. All rights reserved.
Chapter Summary
Installing DOS• The MS-DOS Setup program will partition
and format a hard drive, if needed• Hardware requirements for MS-DOS are
minimal:• An IBM or compatible PC• 6MB of free hard disk space• 512KB of memory
2-59McGraw-Hill/Irwin © 2006 The McGraw-Hill Companies, Inc. All rights reserved.
Chapter Summary
How the FAT File System Works• 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• It is best to use only alphanumeric characters• A file’s extension can indicate the type of file• File attributes determine how DOS handles a
file or directory
• File attributes are read-only, archive, system, hidden, volume label, and directory
2-60McGraw-Hill/Irwin © 2006 The McGraw-Hill Companies, Inc. All rights reserved.
Chapter Summary
Working with the DOS Command Prompt• The ATTRIB command allows you to view
and manipulate the read-only, archive, system, and hidden attributes
• Internal command are part of COMMAND.COM and are always available and fast to access
• CLS, COPY, REN, DEL, MD, RD, CD, and TYPE are internal DOS commands
• External commands are in individual files, which
must be where DOS can find them• XCOPY, DELTREE, FORMAT, FDISK, and
DISKCOPY are external commands
2-61McGraw-Hill/Irwin © 2006 The McGraw-Hill Companies, Inc. All rights reserved.
Chapter Summary
Describe the DOS Bootup Process and Create Startup Disks• It is important to understand the bootup
process of an OS in order to troubleshoot failures that occur during bootup
• A hard boot of a PC occurs when you turn on the power switch
2-62McGraw-Hill/Irwin © 2006 The McGraw-Hill Companies, Inc. All rights reserved.
Chapter Summary
Describe the DOS Bootup Process and Create Startup Disks• A soft boot of a PC occurs when you press
CTRL-ALT-DELETE• Many computers have a Reset button, which
resets a running computer without a power-down and power-up cycle
2-63McGraw-Hill/Irwin © 2006 The McGraw-Hill Companies, Inc. All rights reserved.
Chapter Summary
Describe the DOS Bootup Process and Create Startup Disks• The order of events during bootup of DOS is:
• Cold or warm boot• POST• Bootstrap loader looks on A: or C: drive and
loads the boot record• IO.SYS and MSDOS.SYS are loaded• CONFIG.SYS (if it exists) is read and used by
MSDOS.SYS• COMMAND.COM is loaded
2-64McGraw-Hill/Irwin © 2006 The McGraw-Hill Companies, Inc. All rights reserved.
Chapter Summary
Describe the DOS Bootup Process and Create Startup Disks• DOS bootup order of events (continued)
• AUTOEXEC.BAT (if it exists) is read and used by COMMAND.COM
• The DOS prompt is displayed
• To create a DOS startup disk, you can:• Use the DOS Setup program• Use the SYS or FORMAT command• Use the Startup Disk option in Windows 9x• Format a floppy disk in Windows XP
2-65McGraw-Hill/Irwin © 2006 The McGraw-Hill Companies, Inc. All rights reserved.
Chapter Summary
Troubleshoot Common DOS Problems• A “Non-System Disk” error message means that
the OS loader cannot find IO.SYS or MSDOS.SYS• Most likely cause is a data floppy disk left in drive A:• Remove the floppy and reboot the computer• A “Bad or Missing Command Interpreter” message
means that COMMAND.COM is missing or is a different version than IO.SYS and MSDOS.SYS• Boot from a DOS floppy disk of the correct version,
and copy COMMAND.COM to the root of C:
2-66McGraw-Hill/Irwin © 2006 The McGraw-Hill Companies, Inc. All rights reserved.
Chapter Summary
Troubleshoot Common DOS Problems• A “Bad Command or File Name” error message
means you need to check your spelling and reenter the command
• If you are required to enter the date and time when you boot up a computer there is probably no AUTOEXEC.BAT on the root of the boot disk. Create one, even if it is empty, and most PCs will use the internal clock for the time