Unformatted text preview: All-In-One / CompTIA Network+ All-in-One Exam Guide / Meyers & Jernigan / 170133-8 / Chapter 15 15 C HAPTER Working with the
In this chapter, you will learn how to
• Explain the operation of the command-line interface
• Execute fundamental commands from the command line
• Manipulate files from the command line Whenever I teach a class of new techs and we get to the section on working with the
command line, I’m invariably met with a chorus of moans and a barrage of questions
and statements. “Why do we need to learn this old stuff?” “We’re running Windows
Vista, not Windows 3.1!” “Is this ritualistic hazing appropriate in an IT class?”
For techs who master the interface, the command line provides a powerful, quick,
and elegant tool for working on a PC. Learning that interface and understanding how
to make it work is not only useful, but also necessary for all techs who want to go beyond baby-tech status. You simply cannot work on all PCs without knowing the command line! I’m not the only one who thinks this way. The CompTIA A+ certification
exams test you on a variety of command-line commands for doing everything from
renaming a file to rebuilding a system file.
If you’re interested in moving beyond Windows and into other operating systems
such as Linux, you’ll find that pretty much all of the serious work is done at a command
prompt. Even the Apple Macintosh operating system (OS), for years a purely graphical
operating system, now supports a command prompt. Why is the command prompt so
popular? Well, for three reasons: First, if you know what you’re doing, you can do most
jobs more quickly by typing a text command than by clicking through a graphical user
interface (GUI). Second, a command-line interface doesn’t take much operating system
firepower, so it’s the natural choice for jobs where you don’t need or don’t want (or
can’t get to, in the case of Linux) a full-blown GUI for your OS. Third, text commands
take very little bandwidth when sent across the network to another system.
So, are you sold on the idea of the command prompt? Good! This chapter gives you a
tour of the Windows command-line interface, explaining how it works and what’s happening behind the scenes. You’ll learn the concepts and master essential commands, and
then you’ll work with files and folders throughout your drives. The chapter wraps up with
a brief section on encryption and file compression in the “Beyond A+” section. A good 623 ch15.indd 623 12/8/09 4:58:03 PM All-In-One / CompTIA Network+ All-in-One Exam Guide / Meyers & Jernigan / 170133-8 / Chapter 15 CompTIA A+Certification All-in-One Exam Guide 624 tactic for absorbing the material in this chapter is to try out each command or bit of information as it is presented. If you have some experience working with a command prompt,
many of these commands should be familiar to you. If the command line is completely
new to you, please take the red pill and join me as we step into the matrix. Historical/Conceptual
Operating systems existed long before PCs were invented. Ancient, massive computers
called mainframes and minicomputers employed sophisticated operating systems. It wasn’t
until the late 1970s that IBM went looking for an OS for a new microcomputer—the official name for the PC—the company was developing, called the IBM Personal Computer,
better known as the PC. After being rebuffed by a company called Digital Research, IBM
went to a tiny company that had written a popular new version of the programming
language called BASIC. They asked the company president if he could create an OS for
the IBM PC. Although his company had never actually written an OS, he brazenly said
“Sure!” That man was Bill Gates, and the tiny company was Microsoft.
After shaking hands with IBM representatives, Bill Gates hurriedly began to search for
an OS based on the Intel 8086 processor. He found a primitive OS called Quick-and-Dirty
Operating System (QDOS), which was written by a one-man shop, and he purchased it
for a few thousand dollars. After several minor changes, Microsoft released it as MS-DOS
(Microsoft Disk Operating System) version 1.1. Although primitive by today’s standards,
MS-DOS 1.1 could provide all of the functions an OS needed. Over the years, MS-DOS
went through version after version until the last Microsoft version, MS-DOS 6.22, was
released in 1994. Microsoft licensed MS-DOS to PC makers so they could add their own
changes and then rename the program. IBM called its version PC-DOS.
DOS used a command-line interface. You typed a command at a prompt, and DOS responded to that command. When Microsoft introduced Windows 95 and Windows NT,
many computer users and techs thought that the command-line interface would go
away, but techs not only continued to use the command line, they also needed it to
troubleshoot and fix problems. With Windows 2000, it seemed once again that the
command line would die, but again, that just didn’t turn out to be the case.
Finally recognizing the importance of the command-line interface, Microsoft beefed it
up in Windows XP and then again in Windows Vista. The command line in Windows XP
and in Vista offers commands and options for those commands that go well beyond
anything seen in previous Microsoft operating systems. This chapter starts with some
essential concepts of the command line and then turns to more specific commands. Practical Application
Deciphering the Command-line Interface
So how does a command-line interface work? It’s a little like having an Instant Message
conversation with your computer. The computer tells you it’s ready to receive commands by displaying a specific set of characters called a prompt. ch15.indd 624 12/8/09 4:58:03 PM All-In-One / CompTIA Network+ All-in-One Exam Guide / Meyers & Jernigan / 170133-8 / Chapter 15
All-In-One Chapter 15: Working with the Command-Line Interface 625 Computer: Want to play a game?
Mike: _ You type a command and press ENTER to send it.
Mike: What kind of game?
Computer: _ The PC goes off and executes the command, and when it’s finished, it displays a new
prompt, often along with some information about what it did.
Computer: A very fun game...
Mike: _ Once you get a new prompt, it means the computer is ready for your next instruction. You can give the computer commands in the graphical user interface (GUI) of
Windows as well, just in a different way, by clicking buttons and menu options with
your mouse instead of typing on the keyboard. The results are basically the same: you
tell the computer to do something and it responds.
When you type in a command from the command line, you cause the computer
to respond. As an example, suppose you want to find out the contents of a particular
folder. From the command line, you’d type a command (in this case DIR, but more on
that in a minute), and the computer would respond by displaying a screen like the one
in Figure 15-1. Figure 15-1 Contents of C: directory from the command line In the Windows GUI, you would open My Computer or Computer and click the C:
drive icon to see the contents of that directory. The results might look like Figure 15-2,
which at first glance isn’t much like the command-line screen; however, simply by choosing a different view (Figure 15-3), you can make the results look quite a bit like the
command-line version, albeit much prettier (Figure 15-4). The point here is that whichever interface you use, the information available to you is essentially the same. ch15.indd 625 12/8/09 4:58:04 PM All-In-One / CompTIA Network+ All-in-One Exam Guide / Meyers & Jernigan / 170133-8 / Chapter 15 CompTIA A+Certification All-in-One Exam Guide 626 Figure 15-2
Contents of C:
Icon view Figure 15-3
view in Computer Accessing the Command Line
Before you can use the command-line interface, you have to open it. You can use various methods to do this, depending on the flavor of Windows you are using. Some
methods are simpler than others; just make sure that you know at least one, or you’ll
never get off the starting line! ch15.indd 626 12/8/09 4:58:04 PM All-In-One / CompTIA Network+ All-in-One Exam Guide / Meyers & Jernigan / 170133-8 / Chapter 15
All-In-One Chapter 15: Working with the Command-Line Interface 627 Figure 15-4 Contents of C: in Computer—Details view One easy way to access the command-line interface in Windows 2000 or XP is by
using the Run dialog box. Click the Start button, and then select Run. If you’re using
Windows 2000 or Windows XP, type CMD or COMMAND and press the ENTER key
(Figure 15-5). If you are using Vista, you access the command-line interface through
the Start menu Search box with the same two commands. A window pops up on your
screen with a black background and white text—this is the command-line interface.
Alternatively, buried in the Start menu of most computers, under Programs | Accessories,
is a link to the command-line interface. In Windows 2000, XP, and Vista, it’s called
command prompt. These links, just like the Run dialog box, pull up a nice command
line-interface window (Figure 15-6). If you are displaying the command-line interface
Type CMD in the
Run dialog box to
open a commandline window. Figure 15-6
a C:\ prompt ch15.indd 627 12/8/09 4:58:05 PM All-In-One / CompTIA Network+ All-in-One Exam Guide / Meyers & Jernigan / 170133-8 / Chapter 15 CompTIA A+Certification All-in-One Exam Guide 628 in Windows Vista, notice that it uses a newer version number and copyright date. Also notice that the default user profile directory is C:\Users\User name rather than C:\Documents
and Settings\User name as in previous operating systems (shown in Figure 15-7). To
close the command line-interface window, you can either click the Close box, as on any
other window, or simply type EXIT at any command prompt and press ENTER. Figure 15-7
Vista commandline interface
window If you attempt to enter a command at the Windows Vista command prompt that
requires elevated or administrative privileges, you receive a UAC “Windows needs your
permission to continue” dialog box (you’ll learn more about UAC in the next chapter,
“Securing Windows Resources”). You can also “manually” run a command with elevated privileges by right-clicking a command-prompt shortcut and then selecting Run
as administrator. If you are prompted for administrator password or credentials, enter
them as needed.
NOTE You can also create an administrator shortcut to the Windows Vista
command prompt by right-clicking the Desktop, Select New | Shortcut. Then
for the location of the item, type CMD and click Next. Type CMD to name
the shortcut and click Finish. Your shortcut appears on the Desktop. Next,
right-click the shortcut and select the Advanced button. In the Advanced Properties dialog
box, check the Run as administrator box and click OK. You have now created a Windows
Vista command-prompt shortcut that will always run with administrative privileges. The Command Prompt
The command prompt is always focused on a specific folder. This is important because
any commands you issue are performed on the files in the folder on which the prompt is
focused. For example, if you see a prompt that looks like the following line, you know
that the focus is on the root directory of the C: drive:
C:\> If you see a prompt that looks like Figure 15-8, you know that the focus is on the
C:\Diploma\APLUS\ folder of the C: drive. The trick to using a command line is first to
focus the prompt on the drive and folder where you want to work. ch15.indd 628 12/8/09 4:58:05 PM All-In-One / CompTIA Network+ All-in-One Exam Guide / Meyers & Jernigan / 170133-8 / Chapter 15
All-In-One Chapter 15: Working with the Command-Line Interface 629 Figure 15-8
focus on the C:\
folder NOTE You can hold down the F5 or F8 key during boot-up to access the
Windows 2000, Windows XP, or Windows Vista Advanced Boot Options
menu. This has an option to boot to Safe Mode with Command Prompt,
which loads the GUI into Safe Mode and then overlays that with a commandline interface for rapid access to a prompt. This saves you the step of going to Start | Run
and typing CMD. This is not the old-style command prompt–only interface! Filenames and File Formats
Windows manifests each program and piece of data as an individual file. Each file has
a name, which is stored with the file on the drive. Windows inherits the idea of files
from older operating systemsnamely DOSso a quick review of the old-style DOS
filenames helps in understanding how Windows filenames work. Names are broken
down into two parts: the filename and the extension. In true DOS, the filename could
be no longer than eight characters, so you’ll often see oddly named files on older systems. The extension, which is optional, could be up to three characters long in true
DOS, and most computer programs and users continue to honor that old limit, even
though it does not apply to modern PCs. No spaces or other illegal characters (/ ∴ [ ] |
÷ + = ; , ∗ ?) could be used in the filename or extension. The filename and extension are
separated by a period, or dot. This naming system was known as the 8.3 (eight-dot-three)
Here are some examples of acceptable true DOS filenames:
FRED.EXE SYSTEM.INI FILE1.DOC DRIVER3.SYS JANET CODE33.H Here are some unacceptable true DOS filenames:
4CHAREXT.EXEC WAYTOOLONG.FIL BAD÷CHAR.BAT .NO I mention the true DOS limitations for a simple reason: backward compatibility. Starting with 9x, Windows versions did not suffer from the 8.3 filename limitation. Instead
they supported filenames of up to 255 characters (but still with the three-character
extension) by using a trick called long filenames (LFN). Windows systems using LFN ch15.indd 629 12/8/09 4:58:06 PM All-In-One / CompTIA Network+ All-in-One Exam Guide / Meyers & Jernigan / 170133-8 / Chapter 15 CompTIA A+Certification All-in-One Exam Guide 630 retained complete backward compatibility by automatically creating two names for
every file, an 8.3 filename and a long filename. Modern Windows using NTFS works
almost exactly the same way as LFNs.
Whether you’re running an ancient DOS system or the latest version of Windows
Vista, the extension is very important, because the extension part of the filename tells
the computer the type or function of the file. Program files use the extension .EXE (for
executable) or .COM (for command). Anything that is not a program is some form
of data to support a program. Different programs use different types of data files. The
extension usually indicates which program uses that particular data file. For example,
Microsoft Word uses the extension .DOC (.DOCX for Microsoft Office Word 2007),
while WordPerfect uses .WPD and PowerPoint uses .PPT (.PPTX for Microsoft Office
PowerPoint 2007). Graphics file extensions, in contrast, often reflect the graphics standard used to render the image, such as .GIF for CompuServe’s Graphics Interchange
Format or .JPG for the JPEG (Joint Photographic Experts Group) format.
Changing the extension of a data file does not affect its contents, but without the
proper extension, Windows won’t know which program uses it. You can see this clearly
in My Computer. Figure 15-9 shows a folder with two identical image files. The one on
top shows the Photoshop icon, which is the program Windows will use to open that
file; the one on the bottom shows a generic icon because I deleted the extension. Windows GUI doesn’t show file extensions by default. Figure 15-10 shows the contents of
that same folder from the command line. Figure 15-9
What kind of file
is the one on the
lower right? All files are stored on the hard drive in binary format, but every program has its own
way of reading and writing this binary data. Each unique method of binary organization is called a file format. One program cannot read another program’s files unless it ch15.indd 630 12/8/09 4:58:06 PM All-In-One / CompTIA Network+ All-in-One Exam Guide / Meyers & Jernigan / 170133-8 / Chapter 15
All-In-One Chapter 15: Working with the Command-Line Interface 631 Figure 15-10
One file has no
extension. can convert the other program’s format into its format. In the early days of DOS, no
programs were capable of performing this type of conversion, yet people wanted to
exchange files. They wanted some type of common format that any program could
read. The answer was a special format called American Standard Code for Information
The ASCII standard defines 256 eight-bit characters. These characters include all of
the letters of the alphabet (uppercase and lowercase), numbers, punctuation, many
foreign characters (such as accented letters for French and Spanish—é, ñ, ô—and other
typical non-English characters), box-drawing characters, and a series of special characters for commands such as a carriage return, bell, and end of file (Figure 15-11). ASCII
files, more commonly known as text files, store all data in ASCII format. The ASCII
standard, however, is for more than just files. For example, when you press a key, the
keyboard sends the letter of that key to the PC in ASCII code. Even the monitor outputs
in ASCII when you are running DOS. Figure 15-11
ASCII characters ch15.indd 631 12/8/09 4:58:07 PM All-In-One / CompTIA Network+ All-in-One Exam Guide / Meyers & Jernigan / 170133-8 / Chapter 15 CompTIA A+Certification All-in-One Exam Guide 632 ASCII was the first universal file format. Virtually every type of program—word processors, spreadsheets, databases, presentation programs—can read and write text files.
However, text files have severe limitations. A text file can’t store important information
such as shapes, colors, margins, or text attributes (bold, underline, font, and so on).
Therefore, even though text files are fairly universal, they are also limited to the 256
Even in the most basic text, you need to perform a number of actions beyond just
printing simple characters. For example, how does the program reading the text file
know when to start a new line? This is where the first 32 ASCII characters come into
play. These first 32 characters are special commands (actually, some of them are both
commands and characters). For example, the ASCII value 7 can be either a large dot or
a command to play a note (bell) on the PC speaker. ASCII value 9 is a Tab. ASCII value
27 is an Escape.
ASCII worked well for years, but as computers became used worldwide, the industry
began to run into a problem: there are a lot more than 256 characters used all over the
world! Nobody could use Arabic, Greek, Hebrew, or even Braille! In 1991, the Unicode
Consortium, an international standards group, introduced Unicode. Basic Unicode is
a 16-bit code that covers every character for the most common languages, plus a few
thousand symbols. With Unicode you can make just about any character or symbol
you might imagineplus a few thousand more you’d never even think of. The first 256
Unicode characters are exactly the same as ASCII characters, making for easy backward
A lot of e-mail programs can use Unicode characters, as can Internet message boards
such as my Tech Forums. You can use Unicode characters to accent your writing or simply to spell a person’s name correctly—Martin Acuña—when you address him. Here’s
how you do it.
1. Open a text editing program such as Notepad in the Windows GUI.
2. Hold down the ALT key on your keyboard and, referring to Figure 15-10, press
numbers on your keyboard’s number pad to enter special characters. For
example, pressing ALT-164 should display an ñ, whereas ALT-168 shows a ¿.
3. If you have access to the Internet, surf over to the Tech Forums (www.totalsem.com/
techforum/index.php) and say howdy. Include some Unicode in your post,
of course! Drives and Folders
When working from the command line, you need to be able to focus the prompt at the
specific drive and folder that contains the files or programs with which you want to
work. This can be a little more complicated than it seems, especially in Windows 2000,
Windows XP, and Windows Vista.
At boot, Windows assigns a drive letter (or name) to each hard drive partition and
to each floppy or other disk drive. The first floppy drive is called A:, and the second, if
installed, is called B:. Hard drives usually start with the letter C: and can continue to
Z: if necessary. Optical drives by default get the next available drive letter after the last ch15.indd 632 12/8/09 4:58:07 PM All-In-One / CompTIA Network+ All-in-One Exam Guide / Meyers & Jernigan / 170133-8 / Chapter 15
All-In-One Chapter 15: Working with the Command-Line Interface 633 hard drive. Windows 2000, XP, and Vista enable you to change the default lettering for
drives, so you’re likely to see all sorts of lettering schemes. On top of that, Windows
2000, XP, and Vista let you mount a hard drive as a volume in another drive.
Whatever the names of the drives, Windows uses a hierarchical directory tree to organize the contents of these drives. All files are put into groups Windows calls folders,
although you’ll often hear techs use the term directory rather than folder, a holdover
from the true DOS days. Any file not in a folder within the tree—that is, any file in the
folder at the root of the directory tree—is said to be in the root directory. A folder inside
another folder is called a subfolder. Any folder can have multiple subfolders. Two or
more files with the same name can exist in different folders on a PC, but two files in
the same folder cannot have the same name. In the same way, no two subfolders under
the same folder can have the same name, but two subfolders under different folders can
have the same name.
NOTE It helps to visualize a directory tree as upside down, because in
geekspeak, the trunk, or root directory, is described as “above” the folders
that divide it, and those subfolders “below” root are spoken of as being
“above” the other subfolders inside them. For example, “The file is in the
Adobe folder under Program Files.”
When describing a drive, you use its letter and a colon. For example, the hard drive
would be represented by C:. To describe the root directory, put a backslash (\) after
the C:, as in C:\. To describe a particular directory, add the name of the directory. For
example, if a PC has a directory in the root directory called TEST, it is C:\TEST. Subdirectories in a directory are displayed by adding backslashes and names. If the TEST
directory has a subdirectory called SYSTEM, it is shown like this: C:\TEST\SYSTEM. This
naming convention provides for a complete description of the location and name of
any file. If the C:\TEST\SYSTEM directory includes a file called TEST2.TXT, it is C:\TEST\
The exact location of a file is called its path. The path for the TEST2.TXT file is
C:\TEST\SYSTEM. Here are some examples of possible paths:
D:\ Here are a few items to remember about folder names and filenames:
• Folders and files may have spaces in their names.
• The only disallowed characters are the following eleven: * “ / \ [ ] : ; | = ,
• Files aren’t required to have extensions, but Windows won’t know the file type without an extension.
• Folder names may have extensionsbut they are not commonly used. ch15.indd 633 12/8/09 4:58:08 PM All-In-One / CompTIA Network+ All-in-One Exam Guide / Meyers & Jernigan / 170133-8 / Chapter 15 CompTIA A+Certification All-in-One Exam Guide 634 Mastering Fundamental Commands
It’s time to try using the command line, but before you begin, a note of warning is in
order: the command-line interface is picky and unforgiving. It will do what you say, not
what you mean, so it always pays to double-check that those are one and the same before you press ENTER and commit the command. One careless keystroke can result in the
loss of crucial data, with no warning and no going back. In this section, you’ll explore
the structure of commands and then play with four commands built into all versions
of Microsoft’s command-line interface: DIR, CD, MD, and RD. Structure: Syntax and Switches
All commands in the Windows command-line interface use a similar structure and execute in the same way. You type the name of the command, followed by the target of that
command and any modifications of that command that you want to apply. You can call
up a modification by using an extra letter or number, called a switch or option, which
may follow either the command or the target, depending on the command. The proper
way to write a command is called its syntax. The key with commands is that you can’t
spell anything incorrectly or use a \ when the syntax calls for a /. The command line is
completely inflexible, so you have to learn the correct syntax for each command.
[command] [target (if any)] [switches] or
[command] [switches] [target (if any)] How do you know what switches are allowed? How do you know whether the
switches come before or after the target? If you want to find out the syntax and switches
used by a particular command, always type the command followed by a /? to get help. DIR Command
The DIR command shows you the contents of the directory where the prompt is focused.
DIR is used more often than any other command at the command prompt. When you
open a command-line window in Windows, it opens focused on your user folder. You
will know this because the prompt in 2000/XP will look like this: C:\Documents and
Settings\username>. By typing in DIR and then pressing the ENTER key (remember
that you must always press ENTER to execute a command from the command line), you
will see something like Figure 15-12.
NOTE Some commands give you the same result whether you include
spaces or not. DIR/P and DIR /P, for example, provide the same output. Some
commands, however, require spaces between the command and switches.
In general, get into the habit of putting spaces between your command and
switches and you won’t run into problems. ch15.indd 634 12/8/09 4:58:08 PM All-In-One / CompTIA Network+ All-in-One Exam Guide / Meyers & Jernigan / 170133-8 / Chapter 15
All-In-One Chapter 15: Working with the Command-Line Interface 635 Figure 15-12 DIR in a user’s folder If you are following along on a PC, remember that different computers contain different files and programs, so you will absolutely see something different from what’s
shown in Figure 15-12! If a lot of text scrolls quickly down the screen, try typing DIR
/P (pause). Don’t forget to press ENTER. The DIR /P command is a lifesaver when you’re
looking for something in a large directory.
NOTE Extra text typed after a command to modify its operation, such as
the /W or /P after DIR, is called a switch. Almost all switches can be used
simultaneously to modify a command. For example, try typing DIR /W /P.
When you type a simple DIR command, you will see that some of the entries look
09/04/2008 05:51 PM 63,664 bambi.jpg All of these entries are files. The DIR command lists the creation date, creation time,
file size in bytes, filename, and extension. Any entries that look like this are folders:
12/31/2004 10:18 AM <DIR> WINDOWS The DIR command lists the creation date, creation time, <DIR> to tell you it is a
folder, and the folder name. If you ever see a listing with <JUNCTION> instead of
<DIR>, you’re looking at a hard drive partition that’s been mounted as a folder instead
of a drive letter:
08/06/2006 02:28 PM <JUNCTION> Other Drive Now type the DIR /W command. Note that the DIR /W command shows only the filenames, but they are arranged in five columns across your screen. Finally, type DIR /? to see
the screen shown in Figure 15-13, which lists all possible switches for the command. ch15.indd 635 12/8/09 4:58:08 PM All-In-One / CompTIA Network+ All-in-One Exam Guide / Meyers & Jernigan / 170133-8 / Chapter 15 CompTIA A+Certification All-in-One Exam Guide 636 Figure 15-13 Typing DIR /? lists all possible switches for DIR command Typing any command followed by a /? brings up a help screen for that particular
command. Although these help screens can sometimes seem a little cryptic, they’re
useful when you’re not too familiar with a command or you can’t figure out how to get
a command to do what you need. Even though I have almost every command memorized, I still refer to these help screens; you should use them as well. If you’re really
lost, type HELP at the command prompt for a list of commands you may type. Once
you find one, type HELP and then the name of the command. For example, if you type
HELP DIR, you’ll see the screen shown in Figure 15-13. Directories: The CD Command
You can use the CD (or CHDIR) command to change the focus of the command prompt
to a different directory. To use the CD command, type CD\ followed by the name of
the directory on which you want the prompt to focus. For example, to go to the C:\
OBIWAN directory, you type CD\OBIWAN and then press ENTER. If the system has
an OBIWAN directory, the prompt changes focus to that directory and appears as C:\
OBIWAN>. If no OBIWAN directory exists or if you accidentally type something like ch15.indd 636 12/8/09 4:58:09 PM All-In-One / CompTIA Network+ All-in-One Exam Guide / Meyers & Jernigan / 170133-8 / Chapter 15
All-In-One Chapter 15: Working with the Command-Line Interface 637 OBIWAM, you get the error “The system cannot find the path specified.” If only I had
a dollar for every time I’ve seen those errors! I usually get them because I’ve typed too
fast. If you get this error, check what you typed and try again.
NOTE Consider errors in general for a moment—not just command-prompt
errors such as “Invalid directory,” but any error, including Windows errors.
Many new computer users freeze in horror when they see an error message.
Do not fear error messages. Error messages are good! Love them. Worship
them. They will save you.
Seriously, think how confusing it would be if the computer didn’t tell you when you
messed up. Error messages tell you what you did wrong so you can fix it. You absolutely
cannot hurt your PC in any way by typing the DIR or CD command incorrectly. Take
advantage of this knowledge and experiment. Intentionally make mistakes to familiarize
yourself with the error messages. Have fun and learn from errors!
To return to the root directory, type CD\ and press ENTER. You can use the CD command to point DOS to any directory. For example, you could type CD\FRED\BACKUP\
TEST from a C:\ prompt, and the prompt would change to C:\FRED\BACKUP\TEST\>—
assuming, of course, that your system has a directory called C:\FRED\BACKUP\TEST.
Once the prompt has changed, type DIR again. You should see a different list of files
and directories. Every directory holds different files and subdirectories, so when you
point DOS to different directories, the DIR command shows you different contents.
The CD command allows you to use a space instead of a backslash, a convenient
shortcut. For example, you could go to the C:\WINDOWS directory from the root directory simply by typing CD WINDOWS at the C:\ prompt. You can use the CD [space]
command to move one level at a time, like this:
C:\FRED\BACKUP>CD TEST Or, you can jump multiple directory levels in one step, like this:
C:\FRED\BACKUP\TEST> A final trick: If you want to go up a single directory level, you can type CD followed
immediately by two periods. So, for example, if you’re in the C:\FRED\BACKUP directory and you want to move up to the C:\FRED directory, you can simply type CD.. and
you’ll be there:
C:\FRED> Take some time to move the DOS focus around the directories of your PC, using
the CD and DIR commands. Use DIR to find a directory, and then use CD to move the
focus to that directory. Remember, CD\ always gets you back to the root directory. ch15.indd 637 12/8/09 4:58:09 PM All-In-One / CompTIA Network+ All-in-One Exam Guide / Meyers & Jernigan / 170133-8 / Chapter 15 CompTIA A+Certification All-in-One Exam Guide 638 Moving between Drives
The CD command is not used to move between drives. To get the prompt to point to
another drive (“point” is command-line geekspeak for “switch its focus”), just type the
drive letter and a colon. If the prompt points at the C:\Sierra directory and you want
to see what is on the USB thumb drive (E:), just type E: and DOS will point to the USB
drive. You’ll see the following on the screen:
E:\> To return to the C: drive, just type C: and you’ll see the following:
C:\Sierra> Note that you return to the same directory you left. Just for fun, try typing in a drive
letter that you know doesn’t exist. For example, I know that my system doesn’t have a W:
drive. If I type in a nonexistent drive on a Windows system, I get the following error:
The system cannot find the drive specified. Try inserting a floppy disk and using the CD command to point to its drive. Do the
same with an optical disc. Type DIR to see the contents of the floppy or optical disc.
Type CD to move the focus to any folders on the floppy or optical disc. Now return
focus to the C: drive.
Using the DIR, CD, and drive letter commands, you can access any folder on any
storage device on your system. Make sure you can use these commands comfortably to
navigate inside your computer. Making Directories
Now that you have learned how to navigate in a command-prompt world, it’s time to
start making stuff, beginning with a new directory.
To make a directory, use the MD (or MKDIR) command. To create a directory called
STEAM under the root directory C:, for example, first type CD\ to ensure that you are in
the root directory. You should see the prompt
C:\> Now that the prompt points to the root directory, type MD STEAM to create the
C:\>MD STEAM Once you press ENTER, Windows executes the command, but it won’t volunteer any
information about what it did. You must use the DIR command to see that you have,
in fact, created a new directory. Note that the STEAM directory in this example is not
listed last, as you might expect. ch15.indd 638 12/8/09 4:58:09 PM All-In-One / CompTIA Network+ All-in-One Exam Guide / Meyers & Jernigan / 170133-8 / Chapter 15
All-In-One Chapter 15: Working with the Command-Line Interface 639 C:\>DIR
Volume in Drive C is
Volume Serial Number is 1734-3234
Directory of C:\
07/12/2006 04:46 AM
3 file(s) <DIR>
<DIR> Documents and Settings
bytes free What about uppercase and lowercase? Windows supports both, but it interprets all
commands as uppercase. Use the MD command to make a folder called steam (note
the lowercase) and see what happens. This also happens in the graphical Windows. Go
to your Desktop and try to make two folders, one called STEAM and the other called
steam, and see what Windows tells you.
To create a FILES subdirectory in the STEAM directory, first use the CD\ command to
point the prompt to the STEAM directory:
CD\STEAM Then run the MD command to make the FILES directory:
MD FILES Make sure that the prompt points to the directory in which you want to make the new
subdirectory before you execute the MD command. When you’re finished, type DIR to
see the new FILES subdirectory. Just for fun, try the process again and add a GAMES
directory under the STEAM directory. Type DIR to verify success. Removing Directories
Removing subdirectories works exactly like making them. First, get to the directory that
contains the subdirectory you want to delete, and then execute the RD (or RMDIR)
command. In this example, let’s delete the FILES subdirectory in the C:\STEAM directory.
First, get to where the FILES directory is located—C:\STEAM—by typing CD\STEAM.
Then type RD FILES. If you received no response from Windows, you probably did it
right! Type DIR to check that the FILES subdirectory is gone.
The plain RD command will not delete a directory in Windows if the directory contains files or subdirectories. If you want to delete a directory that contains files or subdirectories, you must first empty that directory by using the DEL (for files) or RD (for
subdirectories) command. You can use the RD command followed by the /S switch to
delete a directory as well as all files and subdirectories. RD followed by the /S switch is
handy but dangerous, because it’s easy to delete more than you want. When deleting,
always follow the maxim “Check twice and delete once.” ch15.indd 639 12/8/09 4:58:09 PM All-In-One / CompTIA Network+ All-in-One Exam Guide / Meyers & Jernigan / 170133-8 / Chapter 15 CompTIA A+Certification All-in-One Exam Guide 640 Let’s delete the STEAM and GAMES directories with RD followed by the /S switch.
Because the STEAM directory is in the root directory, point to the root directory with
CD\. Now execute the command RD C:\STEAM /S. In a rare display of mercy, Windows
responds with the following:
C:\>rd steam /s
steam, Are you sure (Y/N)? Press the Y key and both C:\STEAM and C:\STEAM\GAMES are eliminated. Running a Program
To run a program from the command line, simply change the prompt focus to the folder
where the program is located, type the name of the program, and then press the ENTER key
on your keyboard. Try this safe example. Go to the C:\WINNT\System32 or C:\WINDOWS\
System32 folderthe exact name of this folder varies by system. Type DIR /P to see the files
one page at a time. You should see a file called MEM.EXE (Figure 15-14). Figure 15-14 MEM.EXE displayed in the System32 folder As mentioned earlier, all files with extensions .EXE and .COM are programs, so
MEM.EXE is a program. To run the MEM.EXE program, just type the filename, in this
case MEM, and press ENTER (Figure 15-15). Note that you do not have to type the .EXE
extension, although you can. Congratulations! You have just run your first program
from the command line. ch15.indd 640 12/8/09 4:58:10 PM All-In-One / CompTIA Network+ All-in-One Exam Guide / Meyers & Jernigan / 170133-8 / Chapter 15
All-In-One Chapter 15: Working with the Command-Line Interface 641 Figure 15-15
Running MEM in
Windows Vista NOTE Windows includes a lot of command-line tools for specific jobs such
as starting and stopping services, viewing computers on a network, converting
hard drive file systems, and more. The book discusses these task-specific tools
in the chapters that reflect their task. Chapter 23, “Local Area Networking,”
goes into detail on the versatile and powerful NET command, for example. You’ll read
about the CONVERT command in Chapter 26, “Securing Computers.” I couldn’t resist
throwing in two of the more interesting tools, COMPACT and CIPHER, in the Beyond A+
section of this chapter. Working with Files
This section deals with basic file manipulation. You will learn how to look at, copy,
move, rename, and delete files. You’ll look at the ins and outs of batch files. The examples in this section are based on a C: root directory with the following files and
Volume in drive C has no label.
Volume Serial Number is 4C62-1572
Directory of C:\
04/21/2009 ch15.indd 641 11:37
PM 0 AILog.txt
Documents and Settings
temp 12/8/09 4:58:10 PM All-In-One / CompTIA Network+ All-in-One Exam Guide / Meyers & Jernigan / 170133-8 / Chapter 15 CompTIA A+Certification All-in-One Exam Guide 642 01/10/2008
01/03/2008 07:07 PM
12 Dir(s) 94,630,002,688 bytes free Because you probably don’t have a PC with these files and directories, follow the examples but use what’s on your drive. In other words, create your own folders and copy
files to them from various folders currently on your system. Attributes
Remember way back in Chapter 4, “Understanding Windows,” when you had to make
changes to the folder options in My Computer to see NTLDR, NTDETECT.COM, and
other files? You were actually seeing files with special attributes.
All files have four special values, or attributes, that determine how programs (such as
My Computer in Windows XP or Computer in Windows Vista) treat the file in special
situations. The first attribute is the hidden attribute. If a file is hidden, it is not displayed
when you issue the DIR command. Next is the read-only attribute. A file with a read-only
attribute cannot be modified or deleted. Third is the system attribute, which is used only
for system files such as NTLDR and BOOT.INI. In reality, it does nothing more than
provide an easy identifier for these files. Fourth is the archive attribute, which is used by
backup software to identify files that have been changed since their last backup.
ATTRIB.EXE is an external command-line program you can use to inspect and change
file attributes. To inspect a file’s attributes, type the ATTRIB command followed by the
name of the file. To see the attributes of the file AILog.txt, type ATTRIB AILOG.TXT.
The result is
A AILog.txt The letter A stands for archive, the only attribute of AILog.txt.
Go to the C:\ directory and type ATTRIB by itself. You’ll see a result similar to the
A ch15.indd 642 C:\AILog.txt
C:\t3h0 12/8/09 4:58:10 PM All-In-One / CompTIA Network+ All-in-One Exam Guide / Meyers & Jernigan / 170133-8 / Chapter 15
All-In-One Chapter 15: Working with the Command-Line Interface 643 The letter R means read-only, H is hidden, and S is system. Hey! There are some new
files there. That’s right, some were hidden. Don’t panic if you see a number of files different from those just listed. No two C:\ directories are ever the same. In most cases,
you’ll see many more files than just these. Notice that important files such as NTLDR
and NTDETECT.COM have the system, hidden, and read-only attributes set. Microsoft
does this to protect them from accidental deletion.
You also use the ATTRIB command to change a file’s attributes. To add an attribute
to a file, type the attribute letter preceded by a plus sign (+) as an option, and then type
the filename. To delete an attribute, use a minus sign (–). For example, to add the readonly attribute to the file AILog.txt, type this:
ATTRIB +R AILOG.TXT To remove the archive attribute, type this:
ATTRIB -A AILOG.TXT You can add or remove multiple attributes in one command. Here’s an example of
removing three attributes from the NTDETECT.COM file:
ATTRIB -R -S -H NTDETECT.COM You can also automatically apply ATTRIB to matching files in subdirectories by using
the /s switch at the end of the statement. For example, if you have lots of files in your
My Music folder that you want to hide, but they are neatly organized in many subdirectories, you could readily use ATTRIB to change all of them with a simple command.
Change directories from the prompt until you’re at the My Music folder and then type
ATTRIB +H *.MP3 /S When you press the ENTER key, all your music files in My Music and any My Music
subdirectories will become hidden files.
It’s important for you to know that everything you do at the command line affects
the same files at the GUI level, so run through these steps.
1. In Windows XP, go to My Computer and create a folder in the root directory of
your C: drive called TEST.
2. Copy a couple of files into that folder and then right-click one to see its
3. Open a command-line window and navigate to the C:\TEST folder. Type DIR to
see that the contents match what you see in My Computer.
4. From the command line, change the attributes of one or both files. Make one
a hidden file, for example, and the other read-only.
5. Now go back to My Computer and access the properties of each file. Any changes? ch15.indd 643 12/8/09 4:58:11 PM All-In-One / CompTIA Network+ All-in-One Exam Guide / Meyers & Jernigan / 170133-8 / Chapter 15 CompTIA A+Certification All-in-One Exam Guide 644 Wildcards
Visualize having 273 files in one directory. A few of these files have the extension .DOC,
but most do not. You are looking only for files with the .DOC extension. Wouldn’t it
be nice to type the DIR command so that only the .DOC files come up? You can do this
by using wildcards.
A wildcard is one of two special characters—asterisk (*) and question mark (?)—that
you can use in place of all or part of a filename, often so that a command-line command will act on more than one file at a time. Wildcards work with all commandline commands that take filenames. A great example is the DIR command. When you
execute a plain DIR command, it finds and displays all of the files and folders in the
specified directory; however, you can also narrow its search by adding a filename. For
example, if you type the command DIR AILOG.TXT while in your root (C:\) directory,
you get the following result:
Volume in drive C has no label.
Volume Serial Number is 4C62-1572
Directory of C:\
05/26/2009 11:37 PM
0 Dir(s) 94,630,195,200 bytes free If you just want to confirm the presence of a particular file in a particular place, this
is very convenient. But suppose you want to see all files with the extension .TXT. In that
case, you use the * wildcard, like this: DIR *.TXT. A good way to think of the * wildcard is “I don’t care.” Replace the part of the filename that you don’t care about with an
asterisk (*). The result of DIR *.TXT would look like this:
Volume in drive C has no label.
Volume Serial Number is 4C62-1572
Directory of C:\
07/31/2008 11:37 PM
0 Dir(s) 94,630,002,688 bytes free Wildcards also substitute for parts of filenames. This DIR command will find every
file that starts with the letter a:
Volume in drive C has no label.
Volume Serial Number is 4C62-1572
Directory of C:\
05/29/2009 ch15.indd 644 11:37 PM
0 Dir(s) 94,629,675,008 bytes free 12/8/09 4:58:11 PM All-In-One / CompTIA Network+ All-in-One Exam Guide / Meyers & Jernigan / 170133-8 / Chapter 15
All-In-One Chapter 15: Working with the Command-Line Interface 645 We’ve used wildcards only with the DIR command, but virtually every command
that deals with files will take wildcards. Let’s examine the REN and DEL commands and
see how they use wildcards. Renaming Files
To rename files, you use the REN (or RENAME) command, which seems pretty straightforward. To rename the file IMG033.jpg to park.jpg, type the following followed by the
ren img033.jpg park.jpg “That’s great,” you might be thinking, “but what about using a more complex and descriptive filename, such as Sunny day in the park.jpg?” Type what should work, like this:
ren img033.jpg Sunny day in the park.jpg But you’ll get an error message (Figure 15-16). Even the tried-and-true method of
seeking help by typing the command followed by /? doesn’t give you the answer.
Rename failed me. You can use more complicated names by putting them in quotation marks. Figure 15-17
shows the same command that failed but now succeeds because of the quotation marks.
Success at last. ch15.indd 645 12/8/09 4:58:11 PM All-In-One / CompTIA Network+ All-in-One Exam Guide / Meyers & Jernigan / 170133-8 / Chapter 15 CompTIA A+Certification All-in-One Exam Guide 646 Deleting Files
To delete files, you use the DEL (or ERASE) command. DEL and ERASE are identical
commands that you can use interchangeably. Deleting files is simple—maybe too simple. Windows users enjoy the luxury of retrieving deleted files from the Recycle Bin on
those “Oops, I didn’t mean to delete that” occasions everyone encounters at one time
or another. The command line, however, shows no such mercy to the careless user. It
has no function equivalent to the Windows Recycle Bin. Once you have erased a file,
you can recover it only by using a special recovery utility such as Norton’s UNERASE.
Again, the rule here is to check twice and delete once.
To delete a single file, type the DEL command followed by the name of the file to
delete. To delete the file AILOG.TXT, for example, type this:
DEL AILOG.TXT Although nothing appears on the screen to confirm it, the file is now gone. To confirm
that the AILOG.TXT file is no longer listed, use the DIR command.
As with the DIR command, you can use wildcards with the DEL and ERASE commands to delete multiple files. For example, to delete all files with the extension .TXT
in a directory, you would type this:
DEL *.TXT To delete all files with the filename CONFIG in a directory, type DEL CONFIG.*. To
delete all of the files in a directory, you can use the popular *.* wildcard (often pronounced “star-dot-star”), like this:
DEL *.* This is one of the few command-line commands that elicits a response. Upon receiving
the DEL *.* command, Windows responds with “Are you sure? (Y/N),” to which you
respond with a Y or N. Pressing Y erases every file in the directory, so use *.* with care!
Don’t confuse deleting files with deleting directories. DEL deletes files, but it will not
remove directories. Use RD to delete directories. Copying and Moving Files
Being able to copy and move files in a command line is crucial to all technicians. Because of its finicky nature and many options, the COPY command is also rather painful
to learn, especially if you’re used to dragging icons in Windows. The following triedand-true, five-step process makes it easier, but the real secret is to get in front of a C:\
prompt and just copy and move files around until you’re comfortable. Keep in mind
that the only difference between copying and moving is whether the original is left
behind (COPY) or not (MOVE). Once you’ve learned the COPY command, you’ve also
learned the MOVE command! Mike’s Five-Step COPY/MOVE Process
I’ve been teaching folks how to copy and move files for years by using this handy process. Keep in mind that hundreds of variations on this process exist. As you become more ch15.indd 646 12/8/09 4:58:12 PM All-In-One / CompTIA Network+ All-in-One Exam Guide / Meyers & Jernigan / 170133-8 / Chapter 15
All-In-One Chapter 15: Working with the Command-Line Interface 647 confident with these commands, try doing a COPY /? or MOVE /? at any handy prompt
to see the real power of the commands. But first, follow this process step by step:
1. Point the command prompt to the directory containing the files you want to
copy or move.
2. Type COPY or MOVE and a space.
3. Type the name(s) of the file(s) to be copied/moved (with or without wildcards)
and a space.
4. Type the path of the new location for the files.
5. Press ENTER.
Let’s try an example. The directory C:\STEAM contains the file README.TXT. Copy
this file to a USB thumb drive (E:).
1. Type CD\STEAM to point the command prompt to the STEAM directory.
C:\>CD\STEAM 2. Type COPY and a space.
C:\STEAM>COPY 3. Type README.TXT and a space.
C:\STEAM>COPY README.TXT 4. Type E:\.
C:\STEAM>COPY README.TXT E:\ 5. Press ENTER.
The entire command and response would look like this:
C:\STEAM>COPY README.TXT E:\
1 file(s) copied If you point the command prompt to the E: drive and type DIR, the README.TXT
file will be visible. Let’s try another example. Suppose 100 files are in the C:\DOCS
directory, 30 of which have the .DOC extension, and suppose you want to move those
files to the C:\STEAM directory. Follow these steps:
1. Type CD\DOCS to point the command prompt to the DOCS directory.
C:\>CD\DOCS 2. Type MOVE and a space.
C:\DOCS>MOVE 3. Type *.DOC and a space.
C:\DOCS>MOVE *.DOC 4. Type C:\STEAM.
C:\DOCS>MOVE *.DOC C:\STEAM ch15.indd 647 12/8/09 4:58:12 PM All-In-One / CompTIA Network+ All-in-One Exam Guide / Meyers & Jernigan / 170133-8 / Chapter 15 CompTIA A+Certification All-in-One Exam Guide 648 5. Press ENTER.
C:\DOCS>MOVE *.DOC C:\STEAM
30 file(s) copied The power of the COPY/MOVE command makes it rather dangerous. The COPY/
MOVE command not only lets you put a file in a new location; it also lets you change the
name of the file at the same time. Suppose you want to copy a file called AUTOEXEC.BAT
from your C:\ folder to a thumb drive, for example, but you want the name of the copy on
the thumb drive to be AUTO1.BAT. You can do both things with one COPY command,
COPY C:\AUTOEXEC.BAT E:\AUTO1.BAT Not only does the AUTOEXEC.BAT file get copied to the thumb drive, but the copy also
gets the new name AUTO1.BAT.
As another example, move all of the files with the extension .DOC from the C:\
DOCS directory to the C:\BACK directory and simultaneously change the .DOC extension to .SAV. Here is the command:
MOVE C:\DOCS\*.DOC C:\BACK\*.SAV This says, “Move all files that have the extension .DOC from the directory C:\DOCS
into the directory C:\BACK, and while you’re at it, change their file extensions to .SAV.”
This is very handy, but very dangerous!
Let’s say, for example, that I made one tiny typo. Here I typed a semicolon instead of
a colon after the second C:
MOVE C:\DOCS\*.DOC C;\BACK\*.SAV The command line understands the semicolon to mean “end of command” and therefore ignores both the semicolon and anything I type after it. As far as the command line
is concerned, I typed this:
MOVE C:\DOCS\*.DOC C This, unfortunately for me, means “take all of the files with the extension .DOC in the
directory C:\DOCS and copy them back into that same directory, but squish them all
together into a single file called C.” If I run this command, Windows gives me only one
clue that something went wrong:
MOVE C:\DOCS\*.DOC C
1 file(s) copied See “1 file(s) copied”? Feeling the chilly hand of fate slide down my spine, I do a DIR
of the directory, and I now see a single file called C, where there used to be 30 files with
the extension .DOC. All of my DOC files are gone, completely unrecoverable. XCOPY
The standard COPY and MOVE commands can work only in one directory at a time,
making them a poor choice for copying or moving files in multiple directories. To help ch15.indd 648 12/8/09 4:58:12 PM All-In-One / CompTIA Network+ All-in-One Exam Guide / Meyers & Jernigan / 170133-8 / Chapter 15
All-In-One Chapter 15: Working with the Command-Line Interface 649 with these multi-directory jobs, Microsoft added the XCOPY command. (Note that there
is no XMOVE, only XCOPY.)
XCOPY works similar to COPY, but XCOPY has extra switches that give it the power
to work with multiple directories. Here’s how it works. Let’s say I have a directory on
my C: drive called \DATA. The \DATA directory has three subdirectories: \JAN, \FEB, and
\MAR. All of these directories, including the \DATA directory, contain about 50 files. If
I wanted to copy all of these files to my D: drive in one command, I would use XCOPY
in the following manner:
XCOPY C:\DATA D:\DATA /S Because XCOPY works on directories, you don’t have to use filenames as you would
in COPY, although XCOPY certainly accepts filenames and wildcards. The /S switch,
the most commonly used of all of the many switches that come with XCOPY, tells
XCOPY to copy all subdirectories except for empty ones. The /E switch tells XCOPY to
copy empty subdirectories. When you have a lot of copying to do over many directories,
XCOPY is the tool to use.
Their power and utility make the DEL, COPY/MOVE, and XCOPY commands indispensable for a PC technician, but that same power and utility can cause disaster. Only
a trained Jedi, with The Force as his ally…well, wrong book, but the principle remains:
Beware of the quick and easy keystroke, for it may spell your doom. Think twice and
execute the command once. The data you save may be yours! Working with Batch Files
Batch files are nothing more than text files that store a series of commands, one command per line. The only thing that differentiates a batch file from any other text file is the
.BAT extension. Take a look at Figure 15-18,
and note the unique icon used for a batch file
Text and batch
compared to the icon for a regular text file.
You can create and edit batch files by using
any text editor program—good old Notepad is
often the tool of choice. This is the commandline chapter, though, so let’s dust off the ancient but still important Edit program—it
comes with every version of Windows—and use it to create and edit batch files.
Get to a command prompt on any Windows system and use the CD\ command to
get to the root directory (use C: to get to the C: drive if you’re not on the C: drive by
default). From there, type EDIT at the command prompt to see the Edit program’s interface (Figure 15-19).
Now that you’ve started Edit, type in the two commands as shown in Figure 15-20.
Make sure they look exactly the same as the lines in Figure 15-20.
Great! You have just made your first batch file. All you need to do now is save it with
some name—the name doesn’t matter, but this example uses FIRST as the filename. It
is imperative, however, that you use the extension .BAT. Even though you could probably figure this out on your own later, do it now. Hold down the ALT key to activate ch15.indd 649 12/8/09 4:58:13 PM All-In-One / CompTIA Network+ All-in-One Exam Guide / Meyers & Jernigan / 170133-8 / Chapter 15 CompTIA A+Certification All-in-One Exam Guide 650 Figure 15-19 Edit interface Figure 15-20 Edit with two commands the menu. Press the F (File) key. Then press S (Save). Type in the name first.bat as shown
in Figure 15-21. Press ENTER and the file is now saved.
Now that you’ve saved the file, exit the Edit program by pressing ALT-F and then pressing X (Exit). You’re back at the command prompt. Go ahead and run the program by
typing FIRST and pressing ENTER. Your results should look something like Figure 15-22.
Super! The batch file created a folder and moved the prompt to focus on that folder.
Don’t run the First batch file again or you’ll create another folder inside the first one. ch15.indd 650 12/8/09 4:58:13 PM All-In-One / CompTIA Network+ All-in-One Exam Guide / Meyers & Jernigan / 170133-8 / Chapter 15
All-In-One Chapter 15: Working with the Command-Line Interface 651 Figure 15-21 Saving the batch file Figure 15-22
batch file Let’s now get back to the root directory of C: and edit the FIRST.BAT file again. This
time type EDIT FIRST.BAT and press ENTER. The batch file will come up, ready to edit.
Now change the batch file to look like Figure 15-23. Use the ARROW keys to move your
cursor and the DELETE key to delete.
NOTE Most of the keyboard shortcuts used in WordPad, Word, and so
on, were first used in the Edit program. If you know keyboard shortcuts for
WordPad or Word, many will work in Edit.
The VER command shows the current version of Windows. The ECHO command
tells the batch file to put text on the screen. Run the batch file, and it should look like
Figure 15-24. ch15.indd 651 12/8/09 4:58:14 PM All-In-One / CompTIA Network+ All-in-One Exam Guide / Meyers & Jernigan / 170133-8 / Chapter 15 CompTIA A+Certification All-in-One Exam Guide 652 Figure 15-23 New version of FIRST.BAT Figure 15-24
to show the
of Windows Gee, that’s kind of ugly. Try editing the FIRST.BAT file one more time and add the
following line as the first line of the batch file:
@echo off Run FIRST.BAT again. It should look quite a bit nicer. The @echo off command tells the
system not to show the command, just the result.
Sometimes you just want to look at a batch file. The TYPE command displays the
contents of a text file on the screen, as shown in Figure 15-25.
CAUTION Don’t try using the TYPE command on anything other than a text
file—the results will be unpredictable. ch15.indd 652 12/8/09 4:58:14 PM All-In-One / CompTIA Network+ All-in-One Exam Guide / Meyers & Jernigan / 170133-8 / Chapter 15
All-In-One Chapter 15: Working with the Command-Line Interface 653 Figure 15-25
Using the TYPE
command to see
file contents One of the more irritating aspects to batch files is that sometimes they don’t work
unless you run them in the folder in which they are stored. This is because of the path
setting. Every time you open a command prompt, Windows loads a number of settings
by default. You can see all of these settings by running the SET command. Figure 15-26
shows the results of running the SET command. Figure 15-26 Using the SET command to see settings ch15.indd 653 12/8/09 4:58:15 PM All-In-One / CompTIA Network+ All-in-One Exam Guide / Meyers & Jernigan / 170133-8 / Chapter 15 CompTIA A+Certification All-in-One Exam Guide 654 Don’t worry about understanding everything the SET command shows you, but do
notice a line that starts with Path=. This line tells Windows where to look for a program (or batch file) if you run a program that’s not in your current folder. For example,
let’s say I make a folder called C:\batch to store all of my batch files. I can run the PATH
command from the command prompt to see my current path (Figure 15-27). Figure 15-27 Using the PATH command to see the current path I can then run the PATH command again, this time adding %PATH%;C:\batch
(Figure 15-28). The %PATH% bit is a variable that represents what is currently in the
path. By placing it before my batch folder, I am telling the path command to keep what
is there and just add c:\batch. I can now place all of my batch files in this folder, and
they will always work, no matter where I am in the system. Figure 15-28 Using PATH to add a folder NOTE In Windows 2000 and XP, you can edit the BOOT.INI file by using
the Edit program. Just make sure you use ATTRIB first to turn off the System
and Hidden attributes! In Windows Vista, the boot configuration data (BCD)
store contains boot configuration parameters and objects that control how
the operating system starts. You use the bcdedit.exe command-line tool to add, delete, and
edit the objects and entries stored in the BCD store. ch15.indd 654 12/8/09 4:58:15 PM All-In-One / CompTIA Network+ All-in-One Exam Guide / Meyers & Jernigan / 170133-8 / Chapter 15
All-In-One Chapter 15: Working with the Command-Line Interface 655 And Even More Tools, Utilities, and Commands
As a proficient IT technician in the field, you need to be familiar with a whole slew of
command-line tools and other important utilities. The CompTIA 220-702 exam focuses
in on several of them, and although many have been discussed in detail in previous
chapters, it is extremely important that you understand and practice with CHKDSK,
FORMAT, and SFC. CHKDSK (/f /r)
The CHKDSK (Checkdisk) command scans, detects, and repairs hard drive and volume
related issues and errors. You can run the CHKDSK utility from a command prompt
with the switches /f and /r. The /f switch attempts to fix volume related errors, while the
/r switch attempts to locate and repair bad sectors. To run successfully, CHKDSK needs
direct access to a drive. In other words, the drive needs to be “unlocked.” For example, if
you run CHKDSK /f /r and CHKDSK does not consider your drive unlocked, you will receive a “cannot lock current drive” message, meaning that another process has the drive
locked and is preventing CHKDSK from locking the drive itself. After this, CHKDSK
presents you with the option to run it the next time the system restarts (Figure 15-29). Figure 15-29
/f /r utility and
switches on a
locked drive FORMAT
After the previous chapters, you should have an expert-level knowledge of (or, at the
very least, a passing familiarity with) formatting and partitioning hard drives. Formatting, you may remember, is the process of wiping or preparing a disk to be partitioned
so it can hold an operating system or data. We have already discussed the various builtin Windows utilities available to provide the formatting of drives, and you no doubt
know that a myriad of third-party formatting tools are out there. In this chapter, you
just need to become familiar with the FORMAT command and its switches.
The FORMAT command, you may have guessed, enables you to format disks from the
command line. The very best way to familiarize yourself with FORMAT and its available
switches is simply to enter FORMAT /? from the command prompt. Your results should
be similar to those displayed in Figure 15-30. ch15.indd 655 12/8/09 4:58:16 PM All-In-One / CompTIA Network+ All-in-One Exam Guide / Meyers & Jernigan / 170133-8 / Chapter 15 CompTIA A+Certification All-in-One Exam Guide 656 Figure 15-30 Using Format /? at the command prompt Although the new CompTIA A+ exams focus primarily on operating system formatting utilities and options, you should familiarize yourself with the FORMAT command
and its switches by practicing them on a test system you are literally not afraid to wipe
out. Besides, you never know what skeletons CompTIA may pull out of the closet. SFC (System File Checker)
The Windows SFC (System File Checker), or simply SFC.exe, scans, detects, and restores
important Windows system files, folders, and paths. Techs often use the SFC utility from
within a working version of Windows or from a Windows installation disc to restore
a corrupt Windows environment. If you run SFC and it finds issues, it attempts to replace corrupted or missing files from cached DLLs located in the %WinDir%\System32\
Dllcache\ directory. Without getting very deep into the mad science involved, just know
that you can use SFC to correct corruption. To run SFC from a command prompt, enter SFC /
SCANNOW. To familiarize yourself with SFC’s switches, enter SFC /? (Figure 15-31). ch15.indd 656 12/8/09 4:58:16 PM All-In-One / CompTIA Network+ All-in-One Exam Guide / Meyers & Jernigan / 170133-8 / Chapter 15
All-In-One Chapter 15: Working with the Command-Line Interface 657 Figure 15-31 Checking SFC options with SFC /? at a command prompt Beyond A+
Using Special Keys
You might find yourself repeatedly typing the same commands, or at least very similar
commands, when working at a prompt. Microsoft has provided a number of ways to
access previously typed commands. Type the DIR command at a command prompt.
When you get back to a prompt, press F1, and the letter D appears. Press F1 again. Now
the letter I appears after the D. Do you see what is happening? The F1 key brings back
the previous command one letter at a time. Pressing F3 brings back the entire command
at once. Now try running these three commands:
MD FRED Now press the UP ARROW key. Keep pressing it till you see your original DIR command
it’s a history of all your old commands. Now use the RIGHT ARROW key to add /P to the end
of your DIR command. Windows command history is very handy. Compact and Cipher
Windows XP and Vista offer two cool commands at the command-line interface: COMPACT and CIPHER. COMPACT displays or alters the compression of files on NTFS partitions. CIPHER displays or alters the encryption of folders and files on NTFS partitions. ch15.indd 657 12/8/09 4:58:16 PM All-In-One / CompTIA Network+ All-in-One Exam Guide / Meyers & Jernigan / 170133-8 / Chapter 15 CompTIA A+Certification All-in-One Exam Guide 658 If you type just the command with no added parameters, COMPACT and CIPHER display the compression state and the encryption state, respectively, of the current directory and any files it contains. You may specify multiple directory names, and you may use
wildcards, as you learned earlier in the chapter. You must add parameters to make the
commands change things. For example, you add /C to compress and /U to uncompress
directories and/or files with the COMPACT command, and you add /E to encrypt and
/D to decrypt directories and/or files with the CIPHER command. When you do these
operations, you also mark the directories involved so that any files you add to them in
the future will take on their encryption or compression characteristics. In other words,
if you encrypt a directory and all its files, any files you add later will also be encrypted.
Same thing if you compress a directory. I’ll run through a quick example of each. COMPACT
First let’s try the COMPACT command. Figure 15-32 shows the result of entering the
COMPACT command with no switches. It displays the compression status of the contents of a directory called compact on a system’s C: drive. Notice that after the file listing, COMPACT helpfully tells you that 0 files are compressed and 6 files (all of them)
are not compressed, with a total compression ratio of 1.0 to 1. Figure 15-32 The COMPACT command with no switches If you enter the COMPACT command with the /C switch, it compresses all of the
files in the directory, as shown in Figure 15-33. Look closely at the listing. Notice that
it includes the original and compressed file sizes and calculates the compression ratio
for you. Notice also that the JPG and PNG files (both compressed graphics files) didn’t
compress at all, while the Word file and the PowerPoint file compressed down to around
a third of their original sizes. Also, can you spot what’s different in the text at the bottom of the screen? COMPACT claims to have compressed seven files in two directories!
How can this be? The secret is that when it compresses all of the files in a directory, it ch15.indd 658 12/8/09 4:58:17 PM All-In-One / CompTIA Network+ All-in-One Exam Guide / Meyers & Jernigan / 170133-8 / Chapter 15
All-In-One Chapter 15: Working with the Command-Line Interface 659 Figure 15-33 Typing COMPACT /C compresses the contents of the directory. must also compress the directory file itself, which is “in” the C: directory above it. Thus
it correctly reports that it compressed seven files: six in the compact directory, and one
in the C: directory.
Typing COMPACT again shows you the directory listing, and now there’s a C next to
each filename, indicating that the file is compressed (Figure 15-34). Figure 15-34 The contents of C:\COMPACT have been compressed. Okay, now suppose you want to uncompress a file—say a PowerPoint file, Session 1.ppt.
To do this, you must specify the decompression operation, using the /U switch and the
name of the file you want decompressed, as shown in Figure 15-35. Note that COMPACT
reports the successful decompression of one file only: Session 1.ppt. You could do the
same thing in reverse, using the /C switch and a filename to compress an individual file. ch15.indd 659 12/8/09 4:58:17 PM All-In-One / CompTIA Network+ All-in-One Exam Guide / Meyers & Jernigan / 170133-8 / Chapter 15 CompTIA A+Certification All-in-One Exam Guide 660 Figure 15-35 Typing COMPACT /U "Session 1.ppt" decompresses only that file. CIPHER
The CIPHER command is a bit complex, but in its most basic implementation, it’s
pretty straightforward. Figure 15-36 shows two steps in the process. Like the COMPACT
command, the CIPHER command simply displays the current state of affairs when Figure 15-36 Typing CIPHER /E /A encrypts the contents of the directory. ch15.indd 660 12/8/09 4:58:18 PM All-In-One / CompTIA Network+ All-in-One Exam Guide / Meyers & Jernigan / 170133-8 / Chapter 15
All-In-One Chapter 15: Working with the Command-Line Interface 661 entered with no switches. In this case, it displays the encryption state of the files in the
E:\Work Files\Armor Pictures directory. Notice the letter U to the left of the filenames,
which tells you they are unencrypted. The second command you can see on the screen
in Figure 15-36 is this:
E:\Work Files\Armor Pictures>cipher /E /A This time the CIPHER command carries two switches: /E specifies the encryption
operation, and /A says to apply it to the files in the directory, not just the directory
itself. As you can see, the command-line interface is actually pretty chatty in this case.
It reports that it’s doing the encryption and then tells you what it’s done, and it even
warns you that you should clean up any stray unencrypted bits that may have been left
in the directory.
To confirm the results of the cipher operation, enter the CIPHER command again, as
shown in Figure 15-37. Note that the U to the left of each filename has been replaced Figure 15-37 CIPHER command confirms that the files were encrypted. with an E, indicating an encrypted file. The other indication that this directory has been
encrypted is the statement above the file listing:
New files added to this directory will not be encrypted. Remember that the CIPHER command works on directories first and foremost, and
it works on individual files only when you specifically tell it to do so.
That’s great, but suppose you want to decrypt just one of the files in the Armor Pictures directory. Can you guess how you need to alter the command? Simply add the
filename of the file you want to decrypt after the command and the relevant switches.
Figure 15-38 shows the CIPHER command being used to decipher DSC_4255.dng,
a single file. ch15.indd 661 12/8/09 4:58:18 PM All-In-One / CompTIA Network+ All-in-One Exam Guide / Meyers & Jernigan / 170133-8 / Chapter 15 CompTIA A+Certification All-in-One Exam Guide 662 Figure 15-38 Typing CIPHER /D /A DSC_4255.dng decrypts only that file. Chapter Review Questions
1. The ASCII standard defines how many 8-bit characters?
2. Which of the following is the correct path for a file named YODA.TXT on the C:
drive in a directory called JEDI that’s in a directory called REBELS that’s in the
3. Which of the following commands will delete all of the files in a directory?
A. DEL *.*
B. DEL ALL
C. DEL ?.?
D. DEL *.? ch15.indd 662 12/8/09 4:58:18 PM All-In-One / CompTIA Network+ All-in-One Exam Guide / Meyers & Jernigan / 170133-8 / Chapter 15
All-In-One Chapter 15: Working with the Command-Line Interface 663 4. What command enables you to make a new directory in a Windows XP
5. What command do you type at the Run dialog box to access the command-line
interface in Windows XP?
6. Joey wants to change the name of a file from START.BAT to HAMMER.BAT.
Which of the following commands would accomplish this feat?
A. REN HAMMER.BAT START.BAT
B. REN START.BAT HAMMER.BAT
C. RENAME /S START.BAT HAMMER.BAT
D. RENAME /S HAMMER.BAT START.BAT
7. What types of characters are the asterisk (*) and the question mark (?)?
8. What is the command to make MYFILE.TXT read-only?
A. ATTRIB +R MYFILE.TXT
B. ATTRIB –R MYFILE.TXT
C. READONLY MYFILE.TXT
D. MYFILE.TXT /READONLY
9. To learn the syntax of the DIR command, what can you type?
A. HELP DIR
B. DIR /?
C. DIR /HELP
D. Both A and B. ch15.indd 663 12/8/09 4:58:19 PM All-In-One / CompTIA Network+ All-in-One Exam Guide / Meyers & Jernigan / 170133-8 / Chapter 15 CompTIA A+Certification All-in-One Exam Guide 664 10. What is the command to quit the command-line interface?
D. STOP Answers
1. B. The ASCII standard has 256 characters because that’s all 8 bits can handle!
2. C. You’ll find the YODA.TXT file in the C:\REBELS\JEDI\ folder.
3. A. You can use the *.* wildcard combination to affect every file in a particular
4. C. MD enables you to make a directory or folder. You can also use the older
5. A. Use the CMD command in the Run dialog box to access a command line in
6. B. The REN command with the proper syntax—REN START.BAT HAMMER.BAT—
will rename the file.
7. A. The asterisk and question mark characters are wildcards when used with
8. A. The command ATTRIB +R MYFILE.TXT will make MYFILE.TXT read-only.
9. D. To learn the ins and outs of any command-line program, type the command
followed by the /? switch or else type HELP and then the command.
10. A. Type EXIT and press the ENTER key to bail out of a command-line interface in
Windows. ch15.indd 664 12/8/09 4:58:19 PM ...
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