Explain DOS Internal and External Commands?

Command is an instruction written in a computer acceptable language that user types on the dos prompt. It will execute and do the appropriate action. There are mainly two types of dos command.

Internal commands                   
External commands

1.Internal commands: The internal commands are those commands that are automatically loaded in the memory. Some commonly used DOS internal commands are

1 Cls                          
2. Dir              
3. Date                      
4. Time                      
5. Ver             
6. Copycon               
7. Type          
8. Ren                       
9. Del                         
10. MD                      
11. CD                                   
12. RD                       
13. Copy       

1) Cls :- The purpose of this command is to clear the display screen and redisplay the Dos prompt at the top  left corner of the screen.

Syntax:- C : / > Cls

2) Dir:- It displays the list of directories and files on the screen.

Syntax:- C : / > dir.
     a. C : / > dir/p – It displays the list of directories or files page wise
     b. C: / > dir/w- It displays the list of directories or files width wise
     c. C : / > dir/d: –It display list of directories or files in drive D
     d. C : / > dir filename . extension – It displays the information of specified file.
     e. C : / > dir file name with wild cards.

Wild cards: - It is the set of special characters wild are used with some commonly used DOS commands there are two types of wild cards.

1. Asterisk (*˜)
2. Question mark (?)

1. Asterisk:-  (*) The wild word will match all characters. 
1. C : / > dir *.* - will display list of all files and directories. 
2. C : / > dir R*.* - will display all files stored with first character R.


2. Question mark: - This wild card represents a single character that a group or files have in common.

1) C : / > dir  ac .* ˜- will display all files having any first character and remaining name has given in command.

2) C : / > dir ??? R . doc-will display all files having extension doc and having any first three letters and fourth letter is R.

3) Date: - It displays the current system date. User can also change the current date with new date by using this command.

Syntax: - C : /> date
Current date is: sat 3-25-2015
Enter of new date (mm-dd-yy):-

4. Time : - It displays the current systems time user can also change existing time with new time by using this command.

Syntax : - C : / > time
Current time is 12 : 39 - 48 : 36 p
Enter new time : -

5. VER : It displays the version of DOS being used currently.

Syntax : - C : / > Ver
MS – Dos version 6 : 20
Copy card .

6. copycon : - The purpose of this command is to create  a file.

Syntax : - C : / > copy con filename . extension

Saves the contents of file by pressing  ctrl +z key combination at the last time of the file. File name should not be greater than 11 characters out of which 8 characters are for the name and 3 characters are for the extension.

Extension is optional :
Eg : C : / > copy con ram
I am a good boy
1. File is copied.
C : / >

7. TYPE:- Allows the user to see the contents of a file.

Syntax :- C :/ >Type path
Eg: C:/ > Type D:/> ramu

8. REN : - The purpose of this command is to rename the old file name with new file name.

Syntax : - C : / > ren oldfilename  newfilename
C : / > ren ramu somu

9. DEL:- The purpose of this command is to delete file. The user can also delete multiple files by busing this command and long with while cards.

Syntax : - C : / > Del file name . extension
                  C : / > Del ramu
                  C : Del x . prg.

10. MD:- The purpose of this command is to create a new directly or sub directly i.e sub ordinate to the currently logged directly.

Syntax : - C : /> MD directory
C : /> MD sub directory

Ex : C : / > MD college
Now user wants to create a sub directory first year in college directory then
C : / > cd college
C : / > college > Md first year

11. CD : - The purpose of this command is to change from one director to another directory or sub – directory.

Syntax : - C : / > CD directory name

Ex : C: / > cd college
C : / > college > CD first year
C : / > college > first year >
If the user wants to move to the parents directory then use CD command as
C : / > college > first year > cd ….
C : / > college >

12 . RD: - The purpose of this command is to  remove a directory or sub directory. If the user wants to remove a directory or sub – directory then first delete all the files in the sub – directory and then remove sub directory and remove  empty main directory.

13. COPY: The purpose of this command is to copy one or more specified files to another disk with same file name or with different file name.

Syntax : - C : / > copy source path target path
C : / > copy A :/> ˜ *. * ˜ C : /> chinni
                                         
2. External commands: -  This commands are not permanent part of the memory. To execute or run this commands an external file is required.

Example : [.] Dot  exe, bat.
Some commonly used DOS external commands are .

1. CHKDSK:- The command CHSDK returns the configuration status of the selected disk. It returns the information about the volume, serial number, total disk space, space in directories, space in each allocation unit, total memory and free memory.

Syntax : - C : / > CHKDSK drive name
Eg:- C : / > CHKDSK   e :
If drive name is not mentioned by default current drive is considered.

2. Diskcopy : - Disk copy command is used to make duplicate copy of the disk like Xerox copy. It first formats the target disk and then copies the files by collection. From the source disk and copied to the target disk.

Syntax : - C : / > disk copy < source path > < destination path >
Ex: - c : / > diskcopy A : B :

NOTE: - This command is used after diskcopy command to ensure that disk is copied successfully.

3. Format : - Format is used to erase information off of a computer diskette or fixed drive.

Syntax : - C : / > format drive name
Ex : C : / > format  A:

4. Label : This command is used to see volume label and to change volume label.

Syntax : C : / > label drive name
Ex : C : / > label  A:

5.Scandisk : - This utility is used to repair and check various  disk errors. It also defects various physical disk errors and surface errors.
Syntax : - C : / > scandisk < drive names >
 C : / > Scandisk  A :

6. Move : The purpose of move is move to files from one place to another place.

Syntax: C : / > Move < source path > < target  path >

7. Print :This command allowed users to print a text file to a line printer.
Syntax : C : / > Print  < files name >
C : / > print ramu

8. Tree : This command displays the list of directories and files on specified path using graphical display. It displays directories of files like a tree.

Syntax:- C : / > tree > path
C : / > tree  A:

9. Deltree: This command is used to delete files a directories same as by the del and RD commands. This command is more useful than del and RD commands because it completely removes specified directories ie.,  disk will all it files and sub – directories at a time.

Syntax:- C : /  > deltree (path)

C : / > deltree  A:/>ramu 

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  1. Thk u it helped me so much......

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