Bài giảng Computer - Chapter 16

Chapter Overview Operating System BasicsThe Command Prompt and DOS Mode OperationsFile Systems 1The Software Core2A Short History of MS-DOS3Understanding 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. 4DOS Boot Sequence and Files Three core programs IO.SYSMSDOS.SYSCOMMAND.COM Two optional startup files CONFIG.SYSAUTOEXEC.BAT 5Summary of Steps in Booting the System The power-on self test (POST) runs and invokes the operating system (OS). The read-only memory basic input/output system (ROM BIOS) looks for an OS and checks for IO.SYS and MSDOS.SYS.The OS processes CONFIG.SYS, if present.COMMAND.COM is loaded.The OS processes AUTOEXEC.BAT, if present.COMMAND.COM presents the active-drive prompt. 6The 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. 7The 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. 8Operating 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. 9Windows Resource Management10Memory 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. 11Windows 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. 12The 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. 13Working with the Prompt Typing PROMPT /? or HELP PROMPT provides help information.DOS HELP returns information on customizing the prompt and the information that appears. 14Internal 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. 15DOS 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. 16The 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. 17Creating 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. 18Renaming 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. 19Using Edit20Summary of DOS Terminology 21CONFIG.SYS Commands BUFFERSCOUNTRY DEVICE DEVICEHIGHDOSFCBS FILES INSTALLLASTDRIVEMOUSE.SYS NUMLOCK SHELLSWITCHES22AUTOEXEC.BAT Commands DOSKEY ECHO KEYB MOUSE.EXE PATH PAUSE PROMPT SET SHARE SMARTDRV23File 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. 24Key File System Terms BlockBoot diskBoot sectorClusterDual bootEncryptionEnd-of-file (EOF) markerFileFile allocation table (FAT)File formatFile handleFile lockingFilename FolderFormatLow-level formatMaster boot recordPartition tablePrimary partitionSectorTrack Volume25Comparing and Choosing File Systems Decision factors: Dual boot requirementNumber and size of hard disk drivesSize of partitionsNeed to support legacy applicationsNeed for advanced features such as security 26FAT-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. 27FAT16 and FAT32 Compared and Contrasted High compatibilityUse of MS-DOS bootable floppy diskPerformance advantage on small volumes Manual intervention to use FAT copyNo backup of boot sector 2-GB volume limitBetter performance when operating in real mode or safe mode Dual boot with Windows NT and Windows 98 8.3 filenaming limit Limited compatibilityNo use of MS-DOS bootable floppy diskMore efficient allocation of disk space Automatic use of FAT copy if neededAutomatic backup of boot sector Support of 32-GB volumesFaster load times for applications and large data filesNo dual boot with Windows NT and Windows 98Support of filenames up to 255 characters FAT16FAT3228The NT File System (NTFS) Was introduced with Windows NTSupports long filenames and is optimized for multiuser environmentsProvides file and folder level securityIs more reliable than previous file systemsIs not completely supported under Windows NT 29Advantages and Disadvantages of NTFS Advantages Disadvantages Supports volumes up to 2 terabytes (TB) Maintains a recovery logHas no limit on number of entries at root Allows faster file accessSupports disk quotas (Windows 2000)Supports file and folder compressionSupports 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 98Could decrease performance on volumes smaller than 400 MB 30File 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. 31File 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. 32Chapter 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. 33