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Chapter Overview
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Operating System Basics
The Command Prompt and DOS Mode
Operations
File Systems
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The Software Core
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A Short History of MS-DOS
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Understanding DOS
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All versions were built for a specific class of
CPU.
MS-DOS never overcame critical limitations.
All versions used a command-line interface.
You must use the DOS prompt to set up a
new system or hard disk drive.
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DOS Boot Sequence and Files
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Three core programs
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IO.SYS
MSDOS.SYS
COMMAND.COM
Two optional startup files
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CONFIG.SYS
AUTOEXEC.BAT
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Summary of Steps in Booting the
System
1. The power-on self test (POST) runs and
invokes the operating system (OS).
2. The read-only memory basic input/output
system (ROM BIOS) looks for an OS and
checks for IO.SYS and MSDOS.SYS.
3. The OS processes CONFIG.SYS, if present.
4. COMMAND.COM is loaded.
5. The OS processes AUTOEXEC.BAT, if present.
6. COMMAND.COM presents the active-drive
prompt.
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The DOS File System
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The file is the primary unit of data storage.
Files are organized into directories.
File and directory names can be up to eight
characters long, followed by a period and a
three-character extension.
Some universal extensions are .exe, .com,
.sys, .bat, .txt, .doc, and .drv.
File and directory names are not casesensitive.
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The Evolution of Microsoft Windows
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Early versions presented a graphical user
interface (GUI) for MS-DOS.
Microsoft Windows 3.11 was the last 16-bit
OS and the most well known version.
Microsoft Windows 95 was the first 32-bit
version.
All applications designed for Windows have
standard interfaces.
Multitasking allows users to have more than
one application open.
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Operating Modes
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Real mode could address only 1 MB of
random access memory (RAM).
Standard mode allowed programs to run in
protected mode.
In protected mode, programs could address
up to 16 MB of RAM.
386 enhanced mode could address up to
4 GB of RAM.
Certain applications included a Windows
runtime version.
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Windows Resource Management
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Memory Paging and Virtual Machines
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Virtual memory is an area on the hard disk
drive (called a swap file) that the system uses
to store program code temporarily.
Virtual machines (VMs) allow multiple
programs to operate.
DOS programs run individually in separate
VMs.
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Windows Operating Systems
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Microsoft Windows for Workgroups 3.11 is an
upgrade to Microsoft Windows 3.1.
Windows 95, Microsoft Windows 98, and
Microsoft Windows Me can be networked easily.
Microsoft Windows NT is designed for
networking.
Microsoft Windows 2000 replaces Windows NT.
Upgrading to Windows NT or Windows 2000
could present compatibility problems with some
hardware and applications.
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The COMMAND Command
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MS-DOS uses a text-based command-line
user interface.
A text-based interface requires no drivers
because display functions are built in.
COMMAND.COM provides the user interface.
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Working with the Prompt
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Typing PROMPT /? or HELP PROMPT provides
help information.
DOS HELP returns information on customizing
the prompt and the information that appears.
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Internal and External Commands
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External commands exist as separate files.
Windows has its own set of system utilities.
Internal commands are contained within
COMMAND.COM.
Command mode requires typing a command
instead of clicking an icon.
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DOS Mode Navigation and File
Management
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The DOS file system uses a tree structure.
A fully qualified path is the list of directories
from the root to the file.
The DIR command displays the contents of
the current or a specified directory.
DOS does not support Windows long
filenames.
The MD command creates a new directory.
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The PATH Command
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PATH allows you to display and change the
search path.
%PATH% appends the old path to the new
path.
Programs in path directories can be run from
any location on the computer.
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Creating a Batch File
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A batch file is an executable file that runs a
series of existing commands or applications.
Commands listed in the file are executed in
sequence.
Any executable that can be run from the
prompt can be included in a batch file.
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Renaming a File
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The RENAME or REN command allows you to
rename a file.
The CD command allows you to change
directories.
The CLS command clears the screen.
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Using Edit
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Summary of DOS Terminology
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CONFIG.SYS Commands
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BUFFERS
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FCBS
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MOUSE.SYS
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COUNTRY
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FILES
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NUMLOCK
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DEVICE
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INSTALL
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SHELL
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DEVICEHIGH
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LASTDRIVE
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SWITCHES
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DOS
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AUTOEXEC.BAT Commands
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DOSKEY
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PATH
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SET
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ECHO
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PAUSE
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SHARE
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KEYB
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PROMPT
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SMARTDRV
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MOUSE.EXE
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File System Basics
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The file system organizes data on the storage
medium.
Different media require different file systems.
File systems define naming conventions, file
size, and media capacity.
Magnetic media employ several different file
systems, depending on the OS.
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Key File System Terms
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Block
Boot disk
Boot sector
Cluster
Dual boot
Encryption
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End-of-file
(EOF)
marker
File
File
allocation
table (FAT)
File format
File handle
File locking
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Filename
Folder
Format
Low-level
format
Master boot
record
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Partition
table
Primary
partition
Sector
Track
Volume
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Comparing and Choosing File
Systems
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Decision factors:
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Dual boot requirement
Number and size of hard disk drives
Size of partitions
Need to support legacy applications
Need for advanced features such as security
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FAT-Based File Systems
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All modern PCs can use FAT.
FAT organizes files by listing them in a table.
Two copies of the table are maintained on the
media.
FAT was developed for and is still used by
floppy disk drives.
There are three versions: FAT12, FAT16, and
FAT32.
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FAT16 and FAT32 Compared and
Contrasted
FAT16
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High compatibility
Use of MS-DOS bootable floppy
disk
Performance advantage on
small volumes
Manual intervention to use FAT
copy
No backup of boot sector
2-GB volume limit
Better performance when
operating in real mode or safe
mode
Dual boot with Windows NT and
Windows 98
8.3 filenaming limit
FAT32
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Limited compatibility
No use of MS-DOS bootable
floppy disk
More efficient allocation of disk
space
Automatic use of FAT copy if
needed
Automatic backup of boot sector
Support of 32-GB volumes
Faster load times for
applications and large data files
No dual boot with Windows NT
and Windows 98
Support of filenames up to 255
characters
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The NT File System (NTFS)
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Was introduced with Windows NT
Supports long filenames and is optimized for
multiuser environments
Provides file and folder level security
Is more reliable than previous file systems
Is not completely supported under Windows
NT
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Advantages and Disadvantages of
NTFS
Advantages
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Supports volumes up to
2 terabytes (TB)
Maintains a recovery log
Has no limit on number of
entries at root
Allows faster file access
Supports disk quotas (Windows
2000)
Supports file and folder
compression
Supports file and folder security
Disadvantages
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Does not allow accessing NTFS
volumes under MS-DOS,
Windows 95, or Windows 98
Does not allow using NTFS
volumes as a primary partition
for dual booting MS-DOS,
Windows 95, or Windows 98
Could decrease performance on
volumes smaller than 400 MB
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File System Size Limitations
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Different OSs handle cluster size differently.
Under FAT volumes, drives smaller than
16 MB are formatted as FAT12.
MS-DOS, Windows 95, and Windows 98
cannot access FAT16 volumes larger than
2
GB.
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File System Security
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FAT attributes on FAT file systems
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FAT has attributes that can protect files from being
overwritten or viewed.
Attributes can be set by using the ATTRIB
DOS-mode command, or by right-clicking a file in
Windows and selecting the Properties option.
NTFS file and folder security
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NTFS uses permissions to determine who can
access the file or folder.
Permissions are set by using the Security tab for
the file or folder.
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Chapter Summary
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An OS is the interface between the hardware and the
user.
All OSs have a user interface, memory, and file
management.
Technicians need to know how to perform command
prompt operations.
Technicians who work with older OSs must
understand MS-DOS and DOS startup files.
Internal and external commands can be used to
configure and troubleshoot.
FAT32 has several enhancements over FAT16.
NTFS supports file and folder security, compression,
and disk quotas.
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