Survey%20of%20Operating%20Systems%202nd%20Edition

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Disk Operating System (DOS)
Chapter
2

• Finding DOS and Understanding its Strengths and
  Weaknesses
• Installing DOS
• How the FAT File System Works
• Working with the DOS Command Prompt
• Understanding the DOS Bootup Process
• Troubleshooting Common DOS Problems

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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

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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

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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

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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

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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

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Finding DOS and Understanding its Strengths
and Weaknesses

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

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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

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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

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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

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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

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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

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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

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Installing DOS

• Step-by-Step 2.01
• Installing DOS on a Hard Disk
• Page 55

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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

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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 disks
• The 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.

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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)

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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

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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

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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

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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

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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

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How the FAT File System Works

• Step-by-Step 2.02
• Creating a Simple Batch File
• Page 63

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How the FAT File System Works

• DOS File Attributes
• Determine the manner in which DOS handles files

• Read-only
• Archive
• System

• Hidden
• Volume label
• Directory

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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

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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

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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

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Working with the DOS Command Prompt

• Step-by-Step 2.03
• Using the Online Help in DOS
• Page 68

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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 /?

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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

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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

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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

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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

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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

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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

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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

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Working with the DOS Command Prompt
DOS commands and their functionality
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Working with the DOS Command Prompt

• Step-by-Step 2.04
• Managing Files and Directories
• Page 73

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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.

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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

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Understanding the DOS Boot-Up Process and
Startup Disks

• DOS system files (continued)
• DOS Configuration Files
• CONFIG.SYS adds device drivers and modifies
  DOS settings
• BUFFERS DOS
• DEVICE FILES
• DEVICEHIGH STACKS
• AUTOEXEC.BAT batch file loaded during bootup
• PATH PROMPT SET

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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)

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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

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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

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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

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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

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Understanding the DOS Boot-Up Process and
Startup Disks

• Step-by-Step 2.05
• Create a Startup Floppy Disk Using FORMAT
• Page 83

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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

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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

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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

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Troubleshooting Common DOS Problems

• Bad or Missing Command Interpretererror
  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

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Troubleshooting Common DOS Problems

• 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

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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 dont now

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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

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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

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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

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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

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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 files 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

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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

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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

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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

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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

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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

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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

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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