Copyright Goodheart-Willcox Co., Inc. 45 Chapter 2 Operating Systems table of additional commands. Th ere are many more commands than the few listed, but these are some of the most commonly used. Be aware that there are some com- mands that can only be run by a user with administrative privileges. DOS was the major operating system used by many PCs from 1980 to the late 1990s. However, because DOS was command-line based, it was not considered a user-friendly OS. Users had to memorize many diff erent commands to become pro- ductive with the operating system. Today, text-based commands are still used, especially by system administrators and when troubleshooting. Text-based com- mands are particularly important when a PC fails to complete its startup process and take the user to the GUI. When troubleshooting with system recovery tools, the Windows admin can use the command window to enter text-based commands to check for disk- and fi le-system errors. It is important that the technician be famil- iar with command-line options to be able to use the command prompt eff ectively. Modern Windows systems no longer use DOS. Instead, they are based on the NT kernel. A DOS emulator is provided for backwards compatibility. Th e DOS emulator has the look and feel of a real DOS prompt and functions similarly. Many of the restric- tions or limitations of DOS are not found in the NTDVM. For example, many of the re- stricted characters not allowed in DOS fi le names can be used in the modern Windows command line or DVM because they are supported by the underlying NT kernel. When a computer system fails during the startup process, there is no access to a graphical user interface. Th e best means of communicating with the computer sys- tem is by using a recovery CD or booting to built-in OEM recovery partition. Most of the commands used in Recovery Console look and work exactly like the original DOS commands. Figure 2-6 lists the most commonly used Recovery Console commands. Th ere are also newer text-based commands that complement today’s more sophisticated operating systems. Th ere will be much more about command-line support in Chapter 17. A+ NOTE Text-based commands are still very much a part of the A+ Certifi cation Exams. To pass the exams, you must be familiar with each command’s function. Recovery Console Command Function attrib View or set the attributes of a file or directory cd View or change the current directory chkdsk Check and display the status of a hard drive copy Copy a file del Delete a file dir Display the files, directories, and subdirectories of the current working directory disable Disable a service or a driver diskpart Partition a hard drive enable Enable a service or a driver exit Exit Recovery Console fixmbr Repair the master boot record format Format a hard drive help Display a list of Recovery Console commands md Create a directory ren Rename a file rd Delete a directory Goodheart-Willcox Publisher Figure 2-6 Many of the commands used in Recovery Console look and work exactly like the DOS commands and DOS emulator.