External commands:- This command not prmanent waight of the memory to execute or run these command and external file is required the external fils are; .EXE, .COM, .BAT
VERIOUS EXTERNALS COMMANDS ARE:-
1. EDIT:- This command creates or alters a text file.
Syntext: c:/> edit filename. Extension
2. Attrib:- This command changes or display the attributes of a file.
Syntext: c:/> Atrib filename attributes.
 Verious attributes are:-
1. +R :- It is used to set read only files.
2. -R :- It is used to remove read only files.
3. +H :- This attrib are used to hide the file.
4. -H :- It is used to dehide.
3. Backup:- Perpose of this command is store the verious imported files from the fixed disk to floppy disk as a protects from the verious dameges.
Syntext: c:/>[source drive] [path] [Target drive] [/options]
Verious options are:-
1. /s:- It is used to copy all sub directory.
2. /D:- To copy the file saved on or after given date.
4. Restore:- The backup command copied the file from one this one another to retrits the file which are store using backup command. Restore command is used this command Automatic copy file from file created.
Systext: C:/> Backup [source drive] [Target drive][path][/option]
Verious options are:-
1. S :- To restores all sub directorys.
2. B :- To restores file last modifile.
5. CHKDSK :-This command is used for chacking disk space, computer memory and correcting errores in file. It returns the information about volume, number, total disk space, space use by directory, by files.
Syntext: c:/> CHKDSK<drive name>
6. DISK COPY:- This command is used make a dupplicate copy of disk.
Systext: c:/> Disk Copy<Source Drive><Target drive>
7. DISKCOMP:- This command is used to compare two disk.
Syntext: c:/> diskcomp<source drive><Target drive>
8. DEL TREE:- This command is used to delete all the files and directorys some as Del and RD commands. But it delete spacified directory without Diskette is full or empty.
Syntext: c:/> deltree<Directory name>
9. DOSKEY:- DOSKEY command is the key to display the history of DOS command typed by the user using keyboard.
Syntext: c:/> Doskey/options
10. FORMAT:- This command prepares a blank disk for receiving and storing data.
Syntext:- c:/> Format Target drive
11. X-COPY:- This command selectivly copies files and directory include lower level directorys.
Syntext:- c:/>[source drive][destination drive][/option]
12. LABEL:- It creates, changes or deletes the volume label on a disk.
Syntext: c:/> label<drive name>
13. MORE:- It displays output, one screen at a time and pauses the display after each screenful of data.
Syntext: c:/> more<file name>