Now that most desktop computer operating systems-such as Windows and the Mac OS -- have easy-to-use "point-and-click" graphical user interfaces, fewer people have had experience with text-only systems like DOS. For PC users, however, using DOS still has some advantages. Windows runs older DOS programs very well.
Microsoft's MS-DOS (for Disk Operating System) was designed in 1981 for the original IBM PC, and suffers from many of that computer's limitations. MS-DOS is a simple system that let computer users manage files on floppy disks and run programs. MS-DOS made the most of a computer with little memory or processing power.
The DOS command line is a simple and effective, if
somewhat arcane, way to interact with the computer. The system prompts the
user with a short text string-the familiar C:> or
something similar-when it is ready. The user types in a command which DOS
performs, either displaying results or running a program. The DOS command
line can be frustrating because it requires you to remember the names and
formats of a number of commands. Error messages and feedback from DOS are
often curt or technical.
Since all commands are specified by name, the first
word you type on any command line must be the name of a program or DOS
function. Words following the command are file names, options or other
parameters for the command. The command TYPE SOME.TXT
<Enter> is a simple example. The type command is a DOS
function which displays the contents of a file. The parameter
SOME.TXT is the name of the file to display. DOS makes no
distinction between upper and lower case letters in commands and file
names. However, DOS has no tolerance for typos; if you misspell a command
it bluntly responds with "Bad command or file name."
DOS supports computers with several disk drives, referring to drives by letter: A, B, C, etc. First two drives, A and B are reserved for floppy disks. Drive C is usually the computer's main hard disk. If you had many files on a disk, searching through a list to find a particular one would be very time consuming. To aid in organization, DOS allows files to be grouped in directories, much like organizing papers in manilla file folders. Unlike, manilla folders, you can put directories inside of other directories to organize further. An outline-like view of this directory structure (omitting the files) might look like:
As in the example above, on your computer's hard disk
there will be several directories, some of which may contain further
sub-directories. To access a file, DOS must have the full "path" from the
drive all the way down through levels of directories to the file. To
create a full path, simply string together the directory names, using
backslashes to separate them. For example, the path to a file named
README.TXT in the business directory would be
C:\BUSINESS\README.TXT. Using the full path, the command to
display the contents of README.TXT is TYPE
C:\BUSINESS\README.TXT <Enter>.
Typing full paths can quickly become tedious, so DOS
lets you set a current working directory. The current directory serves as
a starting point for names in the drive and directory hierarchy. It is
usually shown as part of the prompt, so you always know which drive and
directory are current. Changing directories is a simple procedure in DOS;
the CD command (for "change directory") will change the current directory
to wherever specified. After using the command CD C:\BUSINESS
<Enter> to set the current directory, the DOS prompt will
display C:\BUSINESS>. From there, the command to display
README.TXT is TYPE README.TXT <Enter>,
which omits the full path to the file. To return to the top level
directory of the drive, type only a backslash after the CD command. To go
up one level in the directory structure, type two periods
(..) after the CD command.
To switch between drives, all that is required is the
letter of the drive, plus a colon, typed at a prompt. For example, typing
D: <Enter> changes the active drive to D. It is
important to note that DOS keeps track of a separate current directory for
each drive. Changing between drives also returns the user to the directory
last used on that drive. For example if a user was doing work in the
business directory of the C drive (appearing as
C:\BUSINESS> at the prompt), changed to the D drive to
check something, then changed back to the C drive, they would be
automatically placed into C:\BUSINESS>. If you change to a
drive for the first time, you will automatically be placed at the top
level directory of the drive.
The DIR command displays a listing of the contents of
your current directory, along with the amount of space left on the drive.
The output of the command typically displays the size of the files in
bytes (or the word <DIR> for directories), the file or
directory name, and the date the item was last modified. Often times the
contents of a directory will be so numerous that several file listings
will scroll off the screen. Generally you can't merely scroll back to look
at what left the screen in DOS. The DIR command has several options that
provide ways see the listings that scroll by. The command DIR
/W provides a wide listing, minus the modification dates and file
sizes, with directories enclosed in brackets to visually separate them
from files. If you need the more specific information about the files, or
if even the output of DIR /W scrolls off the screen, you can
use the DIR /P command. This command produces the same
listing as the DIR command, but it pauses after a screen-full of
information at a time, waiting for a key press to continue the list. To
get a directory listing of a drive or directory other than your current
directory you can specify the path of the directory as a parameter:
DIR <drive letter><directory name> <Enter>,
or merely DIR <directory name> <Enter>, as
appropriate.
In DOS, you are limited to eight character file names,
with the option of a three character "extension" after a period. File
extensions are used to denote certain types of files, so that programs
know what sort of file they are. Though a file name extension can contain
any three letters, there are some common extensions that are used. The
extension .TXT is often used with plain textfiles,
.DAT with data of some sort, .SYS and
.COM for systems files and certain basic DOS functions,
.EXE for operable programs, and .BAT for
textfiles that contain "batch" commands, usually used by the computer to
perform specific tasks (for example, the file AUTOEXEC.BAT is
run by the computer as the machine boots up). Files with the EXE, COM and
BAT extensions are files that can be run by the user. You can merely type
the file name as a command, without the period or three character
extension, to run them. Typically you won't need to run
ANY.BAT files; they will be run by themselves at the
appropriate time by either DOS or individual pieces of used software. More
advanced users may create their own .BAT files to quickly
carry out an array of tasks.
This isn't an exhaustive list of file name extensions
to be sure. Many pieces of software create files with their own special
extensions to help identify files specifically for use with that
particular package. MegaDots uses .meg to identify a MegaDots
document fil. Extensions such as .wp used by the word
processor "Word Perfect" and .wql created by the spreadsheet
package "Quattro Pro" are but two of many examples. With time and use,
these will be learned and understood at a glance.
Because DOS was designed for simpler computers, the tasks it can perform are relatively simple. It really doesn't do much more than manage files and directories, and run commands and programs.
To create a directory, use the MD command. Typing
MD NEWWORK <Enter> will create a directory named
newwork. In DOS, directories are limited to eight character names, just
like files. Generally directories are left without a file name extension.
The RD command will remove a directory, but not if the directory contains
any files or sub-directories of its own. In that case, you will have to
remove the files and sub-directories first before RD will work.
Copying files from one location to another is easy.
Given a source file, and a destination for the copy, the copy command will
duplicate the file. Typing COPY SOME.TXT D:\STORAGE
<Enter> would copy the file SOME.TXT to the
storage directory on the D drive. Similarly, you could type COPY
D:STORAGE\SOME.TXT to copy the file to your present working
directory. Note that if you omit the destination, DOS assumes you mean the
current directory. A successful operation might look something like this:
C:\BUSINESS> COPY SOME.TXT D:\STORAGE
C:\BUSINESS>
There are several other useful commands for file
manipulation. To view a plain text file without the benefit of a text
editor, you can use the type command along with the file name. Note that
most files are large enough to scroll off the screen in a rapid fashion.
If your document is longer than a few lines, hitting the Pause key (on the
top row of keys, at the far right) will start and stop the display. To
abort the command in the middle of a file, hold down the Control key
(often labelled Ctrl) and press the letter C. Most versions of DOS will
have a built-in editor of some sort, allowing you to just type EDIT
<file name> <Enter> to open and edit a file. This is a
good substitute for playing catch up with rapidly scrolling text and also
allows you to actively move around in a file, instead of merely from start
to finish as type allows.
To remove a file, you can simply type DEL
<file name> <Enter>. If you wish to change the name of
the file, use the rename command.
Typing REN FILE.TXT NEW.TXT <Enter>
will change the name of FILE.TXT to NEW.TXT.
Note if the new file name already exists, an error will be displayed and
the original file will not be renamed. If you wish to overwrite an
existing file, you will need to use the copy command instead. If you have
a large number of files to work with, use "wild cards" to make your file
handling a little easier. Instead of having to type in every file you want
to copy for example, you may be able to use a couple of special characters
to specify a group of files. This would be analogous to some degree to
highlighting several files in Windows before dragging them somewhere, or
performing some other operation. Wild cards are used in place of parts of
the file name specified; you can use * and ? to
take the place of characters to denote a larger group of files. For
example, if I wanted to copy all the files in the current directory with
the extension of .SIM to a floppy disk, I could type
COPY *.SIM A:. Similarly, if I had a group of files that only
differed by a couple of characters in the same place in their file names,
I could use a ? to stand for the character in question. If I
have three files named sam sbm and scm, I could type COPY S?M A:
<Enter> to copy all three files. Note that whereas one
* may denote one or more characters, you must use one
? for each character you intend to replace. Be careful of
typing COPY S*M <Enter> in that situation; some
versions of DOS will not read this correctly, ignoring one or more of the
additional characters. The * is best used to stand for a
group: either all file names with a certain extension, or all extensions
of a certain file name. When in doubt, using ? is the safest.
You can check what files are denoted by a set of characters and wildcards
with the DIR command, typing DIR *.SIM <Enter> for
example.
Should you ever be abruptly greeted with a DOS prompt, or merely wish to play some games you found on the Internet, these commands will help you hit the ground running. Your DOS manual, as well as many fine texts in your local bookstore, will provide you with Many chapters of useful information on getting the most out of DOS.