Most Personal Computers run under the
MSDOS
Operating System.
MSDOS being the Microsoft
Disk Operating System.
It is estimated that almost 10 million machines run under theMSDOS
Operating System and
some 20,000 or more end-user applications have been published to run with
it.
The Operating System
is the program which provides organised services to the computer user and
the application programs that they wish to use. These services consist
mainly of access to the hardware resources such as the disk drives, keyboard,
etc.
The Operating System
has three main constituents:-
-
The system files which are hidden. Their function is to perform such
basic tasks as reading the keyboard, displaying characters on the screen,
opening and closing files etc.
-
The command interrupter, COMMAND.COM which reads commands typed at the
keyboard and attempts to obey them. COMMAND.COM has some simple commands
built in - these are known as internal commands.
-
A series of utility programs covering functions not handled by the internal
commands. There are approximately 52 of these commands, the exact number
varies between different versions of MSDOS
, ranging from COPY to copy files to EDIT the text editor, and many more
Disks and Drives
Because most of your computers Memory
(RAM) is temporary, its
contents are erased when you switch off the power. You need a place to
store the Operating System,
application programs and your work. That's where disks come in, you store
any information you want to keep onto disks.
There are two types of disk: Floppy disks & Hard disks.
Floppy disks (Diskettes)
A disk is a magnetically coated disk of thin plastic, inside a rigid
plastic cover.
You can use Floppy disks to:
-
Transfer information from one computer to another.
-
Store the Operating System,
or application program and your work, if you don't have a Hard disk.
-
Keep a copy of information that you have on your Hard disk (Backup).
You need only format a disk once. After that, you can use the disk again
and again without having to reformat it. Formatting a disk you have previously
used erases any data on the disk, so only reformat a disk if you are sure
you don't need any of the data on it.
Choosing disks
Diskettes come in various forms, so it is important to choose diskettes
that match the type of diskette drive installed in your computer. Several
different types are available :
-
5.25inch 360 Kbyte -
Very rarely used now
-
5.25inch 1.2 Mbyte -
Uncommon but still in use
-
3.5inch 720 Kbyte - Getting
less common, still in use
-
3.5inch 1.44 Mbyte -
The standard in most modern computers.
It should be noted that :-
-
A 720 Kbyte drive can
only read and write to a 720 Kbyte
diskette
-
A 1.44 Mbyte drive can
read and write to both 720 Kbyte
and 1.44 Mbyte diskettes.
However you must use special formatting instructions to format a 720 Kbyte
diskette in a 1.44 Mbyte
drive.
-
The visible difference between a 720 Kbyte
diskette and a 1.44 Mbyte
diskette is that there is no extra notch on a 720 Kbyte
diskette.
Hard disks
A Hard disk is a disk that is enclosed in a permanently sealed metal
housing. Hard disks are better than Floppy diskettes in two main respects:
-
You can store much more information on a Hard disk than on a diskette.
For example, a 40 Mbyte
Hard disk holds the equivalent of almost twenty nine 1.44 Mbyte
Floppy diskettes.
-
They are up to 600 times faster at finding and loading information into
the computers Memory .
Working with Files and Directories
This section introduces you to two of the most fundamental aspects of
using you computer - working with files, and organising those files into
directories.
Files
A file is simply a collection of information that you store on a disk
or diskette. The normal way to create a file is to run an application.
For example, when you use a word processing application to write a letter,
you save the letter by storing it as a file.
In general, each file must have a unique name. However, two files
can share the same name provided that they are on different disks, or in
different directories.
A file name has two parts: the filename itself and an extension.
In this example:
RECIPE.DOC
RECIPE is the filename and DOC is the extension. Note the FULL STOP
between the two parts of the name. When a filename has an extension, the
two parts of the name are separated by a full stop.
Filenames
Choose filenames with care, as a good name will help you to remember
what kind of information is in the file. A filename may contain up to eight
characters.
For example:
PDL, README, 4JULY96, MEMO_MAY
The only characters you cannot use in filenames are:
" / \ [ ] < > + = ; : , ? * { }
Spaces are also not permitted. If in any doubt use only letters
or numbers.
Some filenames to avoid
There are some filenames that you should avoid when naming files because
your computer reserves them for special uses.
AUX, COM1 or COM2The internal name of a device connected to a Serial
Port.
CONThe internal name of data sent to the keyboard or screen.
LPT1, LPT2, LST or PRNThe internal names for the printer connected
to the Parallel port.
Extensions
Use extensions to make your filenames more descriptive. For example
you could add the extension DOC to every document you write. Then when
displaying a list of the files on your disk, you can tell quickly which
files contain documents.
NOTE:- Some applications add their own unique extensions, these should
NOT be altered. If you do the program may not be able to use them. An extension
may contain up to three characters.
These are all valid extensions:
A , TXT, 88, B_2
The same characters are invalid as for filenames, see last page.
Taking care with extensions
There are some extensions to which you computer attaches a special meaning.
Only add these extensions to a file if you are sure the file performs the
correct function:
BAK A backup file. When you save a file, the previous version of
that file MAY be automatically saved as a backup with a BAK extension.
COM or EXE A program or MSDOS
/application file
$$$ An incorrect or compressed file.
Directories
One way of organising the files on your computers Hard disk is to put
them in different directories. Directories enable you to arrange your files
in whatever way you want and get files you need quickly.
Every disk has one basic directory, called the ROOT directory, which
you create automatically when you format the disk. As well as putting files
in this directory, you can also create directories inside it. Each subdirectory
can hold files, and in turn, further subdirectories. The number of subdirectories
on a disk is limited only by the amount of storage space on the disk.
You can visualise a system of directories as an upside-down tree,
with the root directory at the top and the subdirectories branching off
it.
Pathnames
If you use directories, you must tell your computer where to look for
any particular file you want to edit. You do this by specifying the pathname
of the file.
A pathname is a sequence of directory names followed by a filename.
Each directory name is separated from the previous one by a backslash (
\ ). For example the pathname for a file called MEMO.DOC could be :-
C:\USER\PETER\MEMO.DOC
Part 1 Questions
-
What do the Operating
System services consist of ?
-
Give two examples of MSDOS
commands.
-
What must you do first to a new Floppy diskette?
-
What is the most common size and capacity of a Floppy diskette?
-
Give one way in which Hard disks are superior to Floppy disks.
-
What is wrong with each of the names of these files?
-
Give the full pathname for MEMO.DOC
C:\
|
|__ DOS\
|
|__DATA\
| |
| |__ OFFICE\
| |
| |__ MEMO1.DOC
| |
| |__MEMO.DOC
|
|__ WP51\
-
In the following command - COMMAND.COM
Return to DOS menu
E-Mail your answers to:-
dos@butterwick0.freeserve.co.uk