Chapter Overview Operating System Basics The Command Prompt and DOS Mode Operations File Systems

The Software Core

A Short History of MS-DOS

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.

DOS Boot Sequence and Files Three core programs IO.SYS MSDOS.SYS COMMAND.COM Two optional startup files CONFIG.SYS AUTOEXEC.BAT

Summary 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.

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.

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.

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.

Windows Resource Management

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.

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.

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.

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.

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.

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.

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.

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.

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.

Using Edit

Summary of DOS Terminology

CONFIG.SYS Commands BUFFERS COUNTRY DEVICE DEVICEHIGH DOS FCBS FILES INSTALL LASTDRIVE MOUSE.SYS NUMLOCK SHELL SWITCHES

AUTOEXEC.BAT Commands DOSKEY ECHO KEYB MOUSE.EXE PATH PAUSE PROMPT SET SHARE SMARTDRV

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.

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

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

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.

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

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

Advantages and Disadvantages of NTFS 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

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.

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.

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.