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Lecture 1
A Little Bit Of DOS
The Java 2 SDK tools such as javac,
appletviewer, java, etc. that you use to compile and run your Java
programs, must be run from a command prompt window. Using the command
prompt window efficiently requires some rudimentary knowledge of DOS. Read
on to learn some DOS
basics.
What
is DOS?
The
DOS View of Files & Folders
The
useful DOSKEY
Table
of DOS Commands
What
is DOS?
MS-DOS is an operating system with a command-line interface
rather than a graphical user interface.
In Windows you can open a command prompt window
which lets you type in MS-DOS commands. Just click the Start button, point to All Programs,
point to Accessories, and then click Command Prompt.
To end your MS-DOS session, type exit
in the command prompt window at the blinking cursor or just close the command
prompt window by clicking the 
button.
The picture below shows a
typical command prompt window.
DOS
is an entirely text based system. The first thing to note about the command prompt window is the
C:\> prompt
and the blinking cursor next to it. This is where you type in commands.
You
should note that DOS
is entirely case insensitive: so for example,
typing in either "help:" or "HeLp" would bring up a list of
commands you can use.
However, don't forget that Java is not case insensitive.
The
DOS View of Files and Folders
What is this C:\> prompt?
The C represents
your root folder on your hard drive. Every
disk drive has a root folder, which can have subfolders.
The hard disk root folder is usually called the C:\>
while the floppy disk root folder is usually called the A:\
Root
folders can have subfolders which can also have subfolders and so on.
As
an example, here is a Windows Explorer view of some of the folders on my
floppy.
Now lets see the DOS
view of my floppy.
We can see that my
A:\
has a
folder in it called myStuff and there are two subfolders in that folder called
docs and pics.
The docs folder also has a subfolder in it called code.
Now,
to see what's in the code folder
I can type:-
dir
A:\myStuff\docs\code
The
dir command
tells DOS to list all items such as files and subfolders in a
folder.
The rest of the command A:\myStuff\docs\code
is an example of a PATH and tells DOS that I want
the list to be of the items in the code folder. Lets see what I get...
The
third line show I have a file in the code folder
called HelloWorld.java
Understanding Filenames
The
standard DOS filename is comprised of a file name 1 to
8 letters long, then a
period, then a 3-letter extension e.g.
program.exe
data.txt
letter.doc
The
extension to a file's name is indicates what type of file it is. I.e. all
word processor files might have the extension .doc,
while all picture files might have the extension .bmp.
While the user can specify these extensions, many programs use them to
differentiate between formats, and so they have gradually become standardized.
For example, you would expect a .txt file
to be a file containing unformatted text, or a .bmp
file to be in a bit mapped graphics file format.
Understanding Paths
To
completely specify a file on your computer you must specify its drive, it's
folder path and its filename. E.g.
A:\myStuff\docs\code\HelloWorld.java
A path
includes the disk drive and all subfolders needed to specify where the folder
is on a disk. E.g.
A:\myStuff\docs\code
A
colon follows the drive letter and the folder path names are separated by
backward slashes (\), (not forward slashes like internet addresses).
However
a file does not always have to be specified in this complete form: if it
is in the current folder, then you can
just enter its filename.
Current Folder
A useful DOS command
is cd
This tells DOS to
change the current folder. Just like in Windows where you
go into different folders using My Computer, you can change the folder
you are in with DOS too. Here is an example.
cd
A:\myStuff\docs\code
Lets see what happens...
I have
now changed my current folder from A:\ to
A:\myStuff\docs\code
I can tell this is the case because the prompt
has changed from A:\> to
A:\myStuff\docs\code>
Now I can list the items in the code folder in two ways...
dir
A:\myStuff\docs\code
or just
dir
This brings up the same list as before. So,
if you don't specify a path then DOS
assumes that you are referring to your current
folder.
The
Useful DOSKEY
If there is a command you execute very often, you might want to use a small utility called
DOSKEY, which comes free with DOS. The program loads up and stays in the memory. It then 'remembers' the last few commands that are issued at the prompt. To reuse a command, you can make use of the
arrow keys and function keys.
The UP and DOWN arrow keys display the previous command or, if in the middle of the list, the next command.
This trick
saves some typing. You can use various function keys as follows:-
[F7] key: This will display all the commands that are currently stored in
memory. The list displays the commands with a number, that could also be used to call a command quickly.
[F9] key: If you know the
commands number then press [F9] and then the command's number and the command will be displayed on the prompt line.
Rather than remembering silly numbers, that will change when more commands get added to the list and others drop off, you could key in the first few characters and then press
[F8] to recall the command.
[ESC] clears the commands history.
How do you know if you have DOSKEY
running? Type in
doskey /?
at the command prompt and you will get a list of
parameters.
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Note:
-- In Windows XP and 2000, DOSKEY
should be automatically running.
In Windows 98 you
may have to run DOSKEY manually each time you open a command
prompt window by typing doskey at the prompt..
To get it to run automatically every time you open
a command prompt window, access the properties sheet for the command prompt window and add the
command C:\WINDOWS\COMMAND\DOSKEY.COM as the startup batch file.
Now, close the command prompt window. The next time you open an command prompt
window, DOSKEY will load automatically.
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A
Table of DOS Commands
Here
are some useful DOS commands
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A:
- Change current folder path to the floppy disk drive
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C:
- Change current folder path to the hard disk drive
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DIR
- Display current folder contents (show all files and sub- folder). e.g.
A:\myStuff\docs\code>dir
list
all the items in the code folder
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CD
- Change the current folder, e.g.
A:\myStuff\docs\code>cd
C:\docs
changes
the current folder to a folder called docs on
the C drive
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CD
\
- Change the current folder to the root folder. e.g.
A:\myStuff\docs\code>cd
\
changes the current folder to the root folder. In this case the A:
drive is the root. |
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CD..
- Change the current folder to the parent
folder of the folder you are in. e.g.
A:\myStuff\docs\code>CD..
changes
the current folder to
A:\myStuff\docs>
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MD
- Make a new folder. e.g.:
A:\myStuff\docs>md
foo
this
makes a
new subfolder called foo in
the current folder
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RD
- deletes a folder, provided it is empty. e.g.
A:\myStuff\docs>rd
foo
this
deletes a subfolder of docs called
foo
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DEL
- deletes a file. e.g.
A:\myStuff\docs>del
afile.txt
would
delete a file called afile.txt
from the docs folder
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Move - Move file(s) from one place to another.
e.g.
type the following, all on one line...
move
A:\myStuff\docs\code\*.* C:\docs
this
moves all the files in the code folder
on the floppy to a folder called docs
in the C
drive. The *.* means all files. |
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COPY
- Copy file(s) from one place to another.
e.g.
type the following, all on one line...
copy
A:\myStuff\docs\code\*.* C:\docs
this
copies all the files in the code folder
on the floppy to a folder called docs
in the C
drive. The *.* means all files. |
That is folks!!
Now try the DOS
exercise
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