DOS(DISK OPERATING SYSTEM)

 DOS

    The full name of dos is Disk operating system. This is the most popular disk operating system which is applied in Micro computer. Dos developed by Tim Pitterson 1981 named 86-Dos.
Then in July 1981, Microsoft purchased all right to 86-dos, made substantial alternations to it, Ms. Dos as its primary operating system was released in the year 1981. (Named Ms. Dos 1.0)
When Micro Computer with hard disk was developed in 1983, Ms. Dos 2.0 came in to the market. In 1984, Ms. Dos 3.0 and Ms. Dos 4.0 version were developed.
            The latest version of Ms. Dos is Ms. Dos 7.1.

Booting
Loading of in to main memory involves of their essential files of dos such as IO. Sys, MS-DOS. Sys, Command.Com in to the main memory. Loading these files in to main memory is called booting.

Booting Process                                              

                         On

                          ↓

                       RAM

                          ↓

                    BIOS [Basic Input-Output System]

                          ↓

                      POST [Power on Self Test]

                          ↓

        Loads dos on to the memory

                          ↓

                  Dos Prompt

When you switch on the computer. First the BIOS present in its permanent memory tests all the devices. This process is called POST (Power on Self Test) after that the operating system present on the disk is stored in the Dos memory (RAM) and with it the main files of Ms. Dos are executed these files are-

• IO. Sys
• Command.Com
• Ms-Dos. Sys
• Autoexec.Bat
• Config. Sys
• HIMEM. Sys etc

In the end Ms. Dos Prompt is display on the computer screen.

The Dos Prompt
Having loaded the Dos in Ram in the disk, it displays a prompt on the screen, which tells that the system is ready to take instructions from you. This prompt is a way to use the efficiency of Dos. You type your command on this prompt. This command prompt is display in the following way
C:\>_
C:         -           Name of Current Drive
\           -           Name of current Directory
>          -           End of the Prompt
_          -           Cursor

File name in Dos
To decide the file name of file, these are the following rules-
[I]        There can be two parts of a file name-
(a)        Primary Name
            It can be given in maximum 8 characters. Such as Sales, Purchase etc.
(b)        Extension
It maximum, can be fixed 3 characters.
(II)       Dot (.) is used between, primary file name and extension.
(III)      No blank space can be given between the letters of the computer file name.
(IV)      File name of two are more files cannot be similar.
(V)       The command of Ms. Dos can’t be used as file name.
(VI)      Special symbol can’t be used as file names, such as -, [,  ] , /, <,  > etc. 

Dos Commands
Dos commands are two types- 

(1) Internal command

(2) External command

Internal Command
These commands are always available with dos because these commands are automatically stored in the memory at time of booting. All these commands are collected in command.Com program file. Internal commands are DIR, REN,VER etc.

External Command
Eternal command are such short program which are stored either on floppy disk or hard disk and if need be, they are executed and stored in the memory. External Commands are-PROMPT, CHKDSK, EDIT etc.
 
Internal commands of Dos

VER                This command displays the version number of Ms. Dos you are working open.
Syntax-            C :\> VER

VOL                This command displays the volume label and serial number.
Syntax-            C :\> VOL
DATE              This command displays the current data and enables you to reset it
Syntax-            C :\> DATE

TIME              This command display the current time or reset it. 
Syntax-            C :\> TIME
Syntax-            C :\> TIME

CLS                 When you want to clear the screen and get command prompt to the                               first line on screen.
Syntax-            C :\> CLS

COPY CON    This command is used to create file in Dos.
Syntax- C:\> Copy Con <File name>
Example- C:\> Copy Con NIST
After typing the matter we save the file press Ctrl +Z key combination or F6 function key. 

TYPE              This command displays the contents of any file.
Syntax-            C:\> Type <File name>
Example-         C:\> Type NIST

REN                This command is used to change the name of any file.
Syntax- C:\> REN <Old file name> <New file name>

Example-C:\> REN NIST NIST2

COPY             This command is used to make the duplicate copy of any file.

Syntax-            C:\> Copy <Source file name> <Target file name>
Example-C:\> Copy NIST NIST4
Syntax-            C:\> COPY <Path of source file name> <Path of target file name>
Example-C:\> Copy C:\> NIST D:\ NIST5

­

DEL                This command is used to delete the specified file.
Syntax-            C:\> Del <File name>
Example-         C:\> Del NIST

PROMPT        This command changes the Ms. Dos command prompt.
Syntax-            C :\> PROMPT <Prompt Name> or <$Character>
Valid characters for prompt command are given below-
Characters                              Value they give
$q                                                        =
$$                                                        $
$T                                                        Current system time
$D                                                       Current system date   
$P                                                        Current working directory (e.g. - C:\>
$G                                                       >
$L                                                        <
$V                                                       Version number
$N                                                       Default drive
$B                                                        !
Example-

(1)        C:\> Prompt NIST                    Output-            NIST_
(2)        C :\> Prompt $P$G                   Output-            C:\>

CHANGING THE DRIVE
The computer pays attention to only on drive at time. If you want your computer to work in another drive type the name of the drive and the color after it-
Example-         C:\>D:              Output- D:\>

DIR                 This command displays the lists names of all the files and subdirectories under the current working directory. In directory display the following information-

• Dir also lists the drive volume label and volume serial no.
• Display the files and directory name.
• Display files and directory creation date and creation time.
• Display size of files in byte.
• Display number of files and directories in the list.
• Display total space in byte occupied by the files.

Syntax-            C :\> DIR

DIR Command with different switches
We can add switches the list in different ways. The dir commands with switches are as follows-

DIR/P             All the files and directory in the root directory will be display page wise.
DIR/W           All the files and directories the root directories will be display width wise.
DIR/S             Lists the directories with their sub-directories & files.
DIR/L             Display the files & directories name lists in lower case.
DIR/A             Display all types of files (hidden system read-only & normal) in directory listing.
DIR/B             Display the files and directory name list only.
DIR/Y             Display the files & directory listing creation date year in four digits.
DIR/ON         Display the lists directories & file in alphabetical order (A to Z).
DIR/O-N       Display the list directories & file in a reverse alphabetically order largest size.
DIR/OS          Display the files and directories listing by smallest to largest size.
DIR/O-S         Display the files and directories listing by largest to smallest. 
DIR/OD          Display the files & directories listing by oldest to newest date.
DIR/O-D         Display the files and directories listing by newest to oldest date.
DIR/AH           Display the list of hidden file.
DIR/AS            Display the list of system file.
DIR/AR            Display the list of read only files.
 
Wild Card Characters
Two special characters “?”(Question Mark) & “*”(asterisk)  are called will cards in dos similar groups of files are to be copied or deleted this wild cards can be used.

What is question mark (?) Wild Card?
Question wild card is used to introduce one character in the file name. If you want to name a list of those files in (drive) which has 6 characters and their extension name is.EXE. Type the following command-       
C :\> Dir ?????? . Exe

What is Asterisk wild card?
Asterisk wild card is use to display a group of letters in the file name. Support you want to make a list of those files which have their extension name. Exes you will have to type the following command-         
C :\> Dir *.EXE

MKDIRor MD            This command is used to create subdirectories on a disk.
Syntax-C:\> MD <Directory Name>
Example-C:\> MD NIST

CHDIR or CDThis command changes your working directory to the directory you specify.
Syntax-            C:\> CD <Directory Name>
Example-         C:\> CD NIST
CD..                 Makes the parent directory of working directory.
CD\                  Makes the root directory as the current working directory.
RD                   This command is used to remove the directory.
Syntax- C:\> RD <Directory name>
Example-C:\> RD NIST
 
External Command of Dos
EDIT               This command is used to edit the already create file by using copy con command and create a new file.
Syntax-            C:\> EDIT <File name>
Example-         C:\> Edit NIST

LABEL           This command is used to change the disk volume label name.
Syntax- C:\> LABEL

MORE            This command is used to display the long file contents in page wise.
Syntax-            C:\>More <File Name>
Example-C:\>More NIST

MEM               This command displays the current of used and frees memory on your computer.
Syntax-            C:\>MEM

CHKDSK        This command is used to get information about blank space in the disk and memory. It is also used to correct the disorder in the data structure.
Syntax-            C:\> CHKDSK

ATTRIB          This command is used to attribute some features like using this command you can make file hidden or set in to read only form.
Syntax-C:\> ATTRIB <Switch> <file name>
Some switches are as follows-
                        +H       -           Make hidden file
                         -H       -           To turn the file back in to normal mode.
                         +R       -           To set the file in to read only mode.
                         -R       -           To turn the file back in to normal from.
TREE              This command graphically displays the path of each directory and subdirectory on the give drive.
Syntax-[1.]C:\> TREE
[To view the name and paths of all directories and subdirectories on you system.]
[2.]       C:\> TREE/F
[To view file name along with the Directory/ Subdirectory name.]

BATCH FILE A Batch file is used for combining in to one command. When you type the Batch file without the       .BAT extension, the commands in the Batch file are executed. You can create a batch file using any text editor or using Copy Con command.
Syntax-            C:\>Edit <File name>.BAT                   

Or                     C:\>Copy Con <File name>.BAT
 
Autoexec.Bat  Autoexec.Bat is a special batch file that executed automatically when you power up the system or reset it. It can also be executed from Dos by typing Autoexec.

Syntax-            C:\>Copy Con Autoexec.Bat  

 Or                    C:\>Edit Autoexec.Bat