1 Chapter Overview Operating System Basics The Command Prompt and DOS Mode Operations File Systems.
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Transcript of 1 Chapter Overview Operating System Basics The Command Prompt and DOS Mode Operations File Systems.
1
Chapter Overview
Operating System Basics The Command Prompt and DOS Mode
Operations File Systems
2
The Software Core
3
A Short History of MS-DOS
4
Understanding DOS
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.
5
DOS Boot Sequence and Files
Three core programs IO.SYS MSDOS.SYS COMMAND.COM
Two optional startup files 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 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 case-sensitive.
8
The Evolution of Microsoft Windows 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 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
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 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.
13
The COMMAND Command
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.
14
Working with the Prompt
Typing PROMPT /? or HELP PROMPT provides help information.
DOS HELP returns information on customizing the prompt and the information that appears.
15
Internal and External Commands
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
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
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
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
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
BUFFERS
COUNTRY
DEVICE
DEVICEHIGH
DOS
FCBS
FILES
INSTALL
LASTDRIVE
MOUSE.SYS
NUMLOCK
SHELL
SWITCHES
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AUTOEXEC.BAT Commands
DOSKEY
ECHO
KEYB
MOUSE.EXE
PATH
PAUSE
PROMPT
SET
SHARE
SMARTDRV
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File System Basics
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
Block Boot disk Boot sector Cluster Dual boot Encryption
End-of-file (EOF) marker
File File
allocation table (FAT)
File format File handle File locking
Filename Folder Format Low-level
format Master
boot record
Partition table
Primary partition
Sector Track Volume
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Comparing and Choosing File Systems
Decision factors: 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
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
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
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
FAT16 FAT32
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The NT File System (NTFS)
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 Disadvantages
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
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
31
File System Size Limitations
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.
32
File System Security FAT attributes on FAT file systems
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 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.
33
Chapter Summary 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.