LESSON 3: DOS FOR BEGINNERS
DOS stands for Disk Operating System. DOS is the
Operating System, on most PCs, that controls the primary input and
output of your computer while you use an application program such
as your word processor or database.
DOS performs 2 functions:
1. Links the Hardware; 2. Allows for file management
First, it enables the hardware devices to properly communicate with
each other. It is a set of instructions so that the computer's brain
understands how its arms and legs operate (keyboard, monitor, printers,
etc.). We take this ability for granted. It is like starting a car
- many complex systems must work in unison for it to work, yet we
take it for granted that it will start.
The second function of DOS is also important. We must have a means
to manage the files that we save on our Floppy Disks or Hard Drives.
There are times when we wish to copy these files from one disk to
another, erase them, or determine which files are on a disk. These
tasks are performed often and the software required to do so is DOS.
USING DOS
When you access DOS, you will see the lonesome C:\> prompt on
your hard drive.
This symbol signals 3 things:
1. DOS has been properly loaded into RAM
2. "C" is the DEFAULT drive
3. DOS is awaiting your next DOS file management command
Each disk drive and hard disk has a letter associated with it. If
a drive is considered the DEFAULT drive, then the computer will always
assume that the information needed is in that drive, OR if something
you have created is saved, it will be saved to that drive UNLESS you
tell the computer otherwise.
All types of disks contain files. We use DOS as a software tool to
manage these files. We not only tell the computer which file we want
to erase or copy but also which drive it is currently in.
If A:\> is on the screen it is the DOS prompt and in this case
the A: drive is the DEFAULT floppy drive which will be searched for
information if you issue a command and ask DOS to execute it.
You can CHANGE the default drive simply. Let's try switching drives.
At C:\> try the following example: (Example) A: <press enter
key>
The result on screen is now A:\>
The computer now pays attention to A: (A drive). Hopefully there
is a disk in A: drive or DOS gets confused and will give you an error
message.
Since you have a hard drive (which is usually the C: drive,) you
can try switching back and forth between your A: drive and C: in a
similar manner. Try switching around between drives, go back and forth
a few times. Switching drives is a VERY IMPORTANT SKILL, since DOS
pays attention to the default drive whose letter is displayed on your
screen.
FILENAMES & EXTENSIONS
A filename consists of the name and its extension. Files can be typed
in upper or lower case, DOS doesn't care! The file extension frequently
gives a clue as to the nature of the file.
Examples of filenames. LOOK CAREFULLY AT THE THREE DIGIT EXTENSIONS:
123.EXE The program 123, an "executable" file. Think of
as a program that can be started and "run" to do something.
GO.BAT A Batch file (bat). Like an exe file. Contains plain english
DOS commands and can be viewed with the DOS "type" command.
VIEW.COM Unknown file, but a "command" type, similar to
an exe file.
783.WKS A worksheet file from lotus possibly from July of 1983 (7/83)
ME.TXT Probably a text file in plain english. Can be read and viewed
with the DOS command: TYPE
XVC.DBF Unknown file, but we might guess a database program database
file.
CONFIG.SYS A PC system file. Helps "configure" your computer
for specific hookups, and equipment.
SUBDIRECTORIES - LITTLE BOXES IN THE DISK DRIVE
Floppy disks have a relatively limited capacity to store files -
limited in comparison to the seemingly expansive space on a hard drive.
To find a necessary file name on a floppy, just use the DIR or directory
command. However, on a hard disk things get a little out of hand with
hundreds of files all listed on the same screen. A solution is obtained
by adding subdirectories and pathnames to manage the location and
organization of file storage. A path is nothing more than a "trail"
or "direction post" which helps DOS find a particular file
out of the hundreds which may be located on a hard drive.
This pathname is facilitated by the use of multiple directories (called
subdirectories) on a single disk. In this fashion you sort files into
groups in a specific place on the drive. By the way, a subdirectory
is itself a small file and does occupy space on the disk.
You could compare a hard or floppy disk to a department store. The
store might sell toys, books and clothes. Similar items go in the
same department or area.
A disk also has the capacity for many separate areas in which to
place files. DOS refers to these with a main central directory (root
directory) and subdirectories branching below it. You can create a
subdirectory named TEXT which contains all your word processing documents.
Computer utilities could be in a subdirectory called UTIL, and so
on.
WILDCARDS
- ? and * - DOS can use "wildcards" in many operations
(? *).
Simply stated, these wildcards take the place of letters and numbers.
Use the question mark as any SINGLE character. Use the * as any GROUP
of ANY LENGTH of characters. Think of them as shortcuts to get the
job done! Very powerful and useful! Frequently used with the COPY
and DEL commands which are discussed in a few paragraphs.
Example: C>dir A:*.wks
Means provide a directory listing of any files on the A: drive ending
in WKS and beginning with ANY characters of ANY length from 1 to eight
digits. Files such as MY.WKS or NUMBERS.WKS or NAMES.WKS would fit
this description.
Example: B>copy ???.dat A:
Means copy any files to A: drive ending in DAT and having any characters
in the filename AND ONLY filenames exactly three digits long.
The often used *.* means ANY FILE NAME and ANY extension regardless
of length.
For instance: Example: C>copy *.* A: (means copy ALL files from
the existing default C: into the A: drive)
C>copy A:*.* B: (means copy ALL files from A: to B:)
A>del finance.* (delete files from the A: drive which begin with
finance and have ANY file extension size or character type.)
A>Copy *.DOC B: (All files with the extension DOC)
A>Del S*.* (Any file that begins with the letter S)
A>Del B:*.* (ALL files from the B drive - be careful!)
A>Dir B:*.COM (A list of all files with an extension of COM on
the B drive)
INTERNAL & EXTERNAL COMMANDS
Many of the DOS commands once loaded stay inside the machine. These
commands stay resident (stay put) and are called INTERNAL commands.
DIR is an example of an INTERNAL COMMAND - it lives inside the computer
once DOS is loaded.
EXTERNAL COMMANDS only live on disk (Hard or Floppy) and can be copied
to other disks (example: FORMAT.COM). They load TEMPORARILY into the
computer memory, do their job and then are gone. EXTERNAL DOS COMMANDS
MUST HAVE A DOS DISK OR DIRECTORY (OR COPY) of that command in a disk
directory or drive when you need them.
The following are examples of some useful DOS commands:
- DIR - (Internal) means "directory" (a list of files or
programs on the disk.)You get a listing of files in the drive (hopefully
a disk is in the drive.) Notice that we added /p to the end of a command.
C> Dir (List all files)
C> Dir A: (List on files on diskette)
C>dir/p <enter> Show a list of all files and "pause
after each screenful."
- COPY - (Internal) copies one or several files to a disk or directory.
Copy can duplicate a file onto another disk or into a subdirectory
(more on subdirectories later). Copy is a very flexible and powerful
DOS commands. Use the copy command with the wildcards seen above for
even more flexibility.
Example: B>copy zip.doc A: (copy zip.doc from B: drive to A: drive.)
Example: A>copy C:why.com B: (copy why.com from C: drive to B:
drive.)
Example: C>copy C:fuss.txt B:whine.txt (copy fuss.txt from C:
drive to B: drive and rename it whine.txt)
Remember, if the computer is not told differently, it will assume
the DEFAULT
drive:
A>COPY A:sample.wk1 B: is the same as:
A>COPY sample.wk1 B:
The "A:" in the first example is redundant.
- DATE and TIME - (Internal) A calendar and clock exist within DOS.
On some computers it automatically is updated and kept current. Date
and time data is important to DOS since it is attached to all files
to keep track of when they were created so you can determine which
file is most recent.
Example: B>time Example: A>date
- DEL or ERASE - (Internal) deletes files or groups of files.
Use DEL*.* to erase all files from a disk. See our previous mention
of wildcards (* and ?). Deleting old files is a necessary operation,
though, which frees up space on a disk.
Example: A>del whine.txt Example: B>del 784.jid
Example: A>del *.jid (notice the use of the * wildcard we mentioned
earlier!)
Example: A>del old.* (notice the use of the * wildcard we mentioned
earlier!)
- DISKCOPY - (External) copies entire contents of one floppy to another.
Diskcopy is a wise idea since disks wear out after several hundred
hours of operation. All information on the target disk will be destroyed
and over-written with the new information, so be careful!
Example: A>diskcopy A: B: (copy the contents of A: floppy to B:
floppy)
- CLS - (Internal) clears the screen and puts the cursor in the home
(upper left) position. Useful. Try it!
Example: A>cls
- CD or CHDIR - (Internal) changes the current (active) subdirectory
or directory. CD\ brings you to the root (main directory) no matter
where you are.
C> CD\WINDOWS (Change to Windows directory)
C> CD\ (Change to the root directory)
- FORMAT - (External) Prepares a blank floppy to receive data. Format
erases any old files on a disk - be careful! Format prepares the tracks
and sectors which will receive the data. All disks must first be formatted
prior to use.
Example: B>format A: (format floppy in A: drive)
Example:C>format A:/s (format floppy in A: AND add system files)
Tip:DANGER! If you enter any of these commands, your files are off
to Computer Heaven, never to be seen again.
A>format C: wipes out your hard drive!
Also C> del *.* wipes out hard drive.
- SCANDISK - (External) This is an advanced disk utility. It will
check the disk and highlight any problem areas. It uses a Graphical
User Interface.
PRACTICE: FREQUENTLY USED DOS COMMANDS
B>rd\letters\financial (removes financial subdirectory below letters
subdirectory and root directory)
A>md data (make directory data)
Example: A>cd\ (change to the root or uppermost directory)
Example: C>cd\data (change to subdirectory named data below the
root)
A>DIR B:
A>DIR B:/P - Displays list of files one screen at a time
A>DIR B:/W - Displays list of files using the entire width of
the screen
A>COPY A:filename.ext B: - To copy one file from Disk A to Disk
B
A>DEL B:filename.ext - To remove the specified file from the specified
drive.
A>DISKCOPY A: B: - Making an exact copy of the diskette in Drive
A onto the diskette in Drive B. (Follow on-screen directions)
TUTORIAL QUESTIONS (DOS FOR BEGINNERS)
1. State the uses of 5 Internal commands and 5 external commands.
2. What is the difference between Internal and External commands?
3. Explain the following: Directories, Format, Rename, Path, Full
pathname.
4. Give 5 specific and original examples of the use of wildcards.
5. Name the 5 most important DOS commands and state why they are
important.
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