External commands

External commands are known as Disk residence commands. Because they can be store with DOS directory or any disk which is used for getting these commands. Theses commands help to perform some specific task. These are stored in a secondary storage device. Some important external commands are given below-

1. MORE:-Using TYPE command we can see the content of any file. But if length of file is greater than 25 lines then remaining lines will scroll up. To overcome through this problem we uses MORE command. Using this command we can pause the display after each 25 lines.

Syntax:- C:\> TYPE <File name> | MORE
C:\> TYPE ROSE.TXT | MORE
or
C:\> DIR | MORE

2. MEM:-This command displays free and used amount of  memory in the computer.

Syntax:- C:\> MEM
the computer will display the amount of memory.

3. SYS:- This command is used for copy system files to any disk. The disk having system files are known as Bootable Disk, which are used for booting the computer.

Syntax:- C:\> SYS [Drive name]
C:\> SYS A:
System files transferred 
This command will transfer the three main system files COMMAND.COM, IO.SYS, MSDOS.SYS to the floppy disk.

4. XCOPY:- When we need to copy a directory instant of a file from one location to another the we uses xcopy command. This command is much faster than copy command.

Syntax:- C:\> XCOPY < Source dirname >  <Target dirname>
C:\> XCOPY  TC TURBOC

5. MOVE:- Move command is used for moving one file or multiple files from one location to another location or from one disk to another disk.

Syntax:- C:\> MOVE  <file name>  <path name>
C:\SONGS> MOVE   *.MP3   C:\ SONGS\OLD SONGS\

C:\>

6. FC:-(File Compare) This command is capable for comparing two set of files and display difference between two files.

Syntax:- C:\> FC <First set of file>  <Second set of file>
C:\> FC ROSE.TXT GULAB.TXT

7.CHKDSK:-(Check disk) - This command is used to check the status of a disk and show the report of result status.

Syntax:- C:\> CHKDSK

C:\>CHKDSK

CHKDSK has NOT checked this drive for errors.
You must use SCANDISK to detect and fix errors on this drive.

Volume JAI created 10-19-2001 7:14p
Volume Serial Number is 3E42-1907

4,203,073,536 bytes total disk space
381,988,864 bytes available on disk

4,096 bytes in each allocation unit
1,026,141 total allocation units on disk
93,259 available allocation units on disk

651,264 total bytes memory
610,784 bytes free

Instead of using CHKDSK, try using SCANDISK. SCANDISK can reliably detect
and fix a much wider range of disk problems.
8. SORT:- This command is useful when we want to sort a file. When we run this command the result can be get to display device or file.

Syntax:- C:\> SORT /R  < Input file name>  <output file name>
Suppose we have a file Player.txt which having the list of a cricket player team and we want to sort the list of players, then we uses this command
C:\> SORT  Player.txt

If we not specify the output file name then result will show to the screen.

/R- switch is used for sorting the file in descending order like from Z to A or from 9 to 0.

9. FIND:- The FIND command is used to search a file for a text string. 

Syntax:- C:\> FIND "String to search" <File name>
C:\TEST>find "office" gulab.txt

---------- gulab.txt
A clock in a office can never get stolen

10. DISKCOPY:- DISKCOPY copies the contents of a floppy disk to another.

Syntax:- C:\> DISKCOPY  <Drive1>  <Drive2>
C:\> DISKCOPY  A:   B:

This command will be copy all contents of A drive to B drive.

11. ATTRIB:- Sets the various type of attribute to a file. Like Read only, Archive, Hidden and System attribute.

Syntax:- C:\> ATTRIB [± r] [± a] [± h] [± s] <File name>
here r  -  for read only,  a-  for archive, h  -  for hidden, s -  for hidden attribute.
C:\> ATTRIB +r  Gulab.txt
This command will change the attribute of file gulab.txt to read only mode. To remove the read only attribute we will follow this command.
C:\> ATTRIB -r Gulab.txt

12. LABEL:- If you are not happy with the volume label of hard disk, you can change it.

Syntax:- C:\> LABEL
C:\>LABEL
Volume in drive C is JAI
Volume Serial Number is 3E42-1907
Volume label (11 characters, ENTER for none)? INFOWAY


13. DOSKEY:- Once we install doskey , our dos will star to memorize all commands we uses. We can recall those commands using up or down arrow keys. It also gives the facility to create macros, which creates a short key for long keyword or command. 

Key function for Doskey are given as-

UP,DOWN arrows recall commands
Esc clears current command
F7 displays command history
Alt+F7 clears command history
F9 selects a command by number
Alt+F10 clears macro definitions
Syntax:- C:\> DOSKEY
DOSKey installed

Creating Macros:-
C:\>doskey t=time

C:\>t
C:\>time
Current time is 3:39:05.97p
Enter new time:

To list out all macros defined just type DOSKEY/MACROS at dos prompt and press enter.
C:\>DOSKEY/MACROS
$D=date
T=time

14. FORMAT:- This command creates new Track & Sectors in a disk. Every

Syntax:- C:\> FORMAT  [drive name] [/S]
C:\> FORMAT A:
this command will create new track & sectors.
C:\> FORMAT A: /S
This command will transfer system files after formatting the disk.

Wildcard commands

Wildcard commands are used when we are working with multiple files instant of a single file at a time. These commands uses '?' and '*' symbol.

The '?' wildcard character

Suppose we want to list out all the files and directories which have primary file name made of four characters and secondary name made of 3 characters. then here we use DIR command with following switches

C:\> DIR ????.???

Here a '?' symbol represent that ? can be a any character or it may be special symbols.

Suppose we want to list out all the files which primary field name made of  4 characters, the first character start with 'C' and secondary name is 'EXE'. Then we uses

C:\> DIR C???.EXE

The '*' wildcard character

If we want to list all the files with extension .EXE the the command we give is-

C:\> DIR *.EXE

If we want to display all files with first character 'D' and extension 'EXE' in floppy disk, then we give the command

C:\> DIR A: D*.EXE

Some Internal commands with wild card

COPY:-If we have to copy the songs from our CD drive to our Hard disk. Then we suppose E:\ is our CD drive and we have to store all the songs in C:\ SONGS directory.

C:\> COPY   E:\ *.MP3   C:\ SONGS

REN:- If we want to rename all the files which have extension of 'TXT' to extension 'MSG' then we give the command

C:\> REN  *.TXT   *.MSG

DEL:- If we want to erase those files which have the extension of 'TMP' from our disk then we uses the command

C:\> DEL  *.TMP
If we use /p switch the computer give ask every time before deleting the file. If we enter 'Y' the it will erase the file from disk either it will leave the file.

Internal Commands

These commands are automatic loaded into the memory when operating system is loaded into the memory. Thus these are also called memory-resident commands. The command available are all combined together and are stored in Command.com file, which is a executable command file. These internal command are further grouped according to their properties. These are as follows.

Genral purpose

File related commands Directory related commands

1. CLS

2. DIR 

3. VER

4. VOL

5. DATE

6. TIME

7. COPY CON

8. TYPE

9. COPY

10. REN

11. DEL

12. MD

13. CD

14. RD

General purpose commands

1. CLS:- (Clear the screen) This command is used to clear the screen or wipe out every thing written on the screen.

Syntax:-    C:\> CLS   and press Enter

2. DIR:- (Directory) Dir command is used for listing files and directories present in the current disk.

Syntax:-  C:\> DIR [/switches]

Example:-   C:\> DIR /P

 

Switches:-

/P Page wise

/W Widths wise

/S List all files and directory of subdirectories

/AH Display directory with hidden files

/AS Display directory with system files

/AD Display only directories present in current drive

3. VER:-(Version) Version numbers indicates that which edition of DOS we are working on.

Syntax:-  C:\> VER   press enter

Output:-

C:\>VER

Windows 98 [Version 4.10.2222]

4. VOL:-(Volume) Displays the disk volume label and serial number, if it exist.

Syntax:- C:\> VOL  press enter

Output:-C:\>VOL

Volume in drive C is JAI

Volume Serial Number is 3E42-1907

5. DATE:- Display the current Date

Syntax:-  C:\> DATE

C:\>DATE

Current date is Fri 02-15-2002

Enter new date (mm-dd-yy):

Type DATE without parameters to display the current date setting and

a prompt for a new one. Press ENTER to keep the same date.

Note:- We enter new date in the format of MM-DD-YY.

6. TIME:- Display current time

Syntax:- C:\> TIME

C:\>TIME

Current time is 8:38:47.70a

Enter new time:

Type TIME with no parameters to display the current time setting and a prompt for a new one. Press ENTER to keep the same time.

Note:- We enter the time in the format of 24 hour clock.

File related commands

7. COPY CON:- This command gives the facility to create a new text file.

Syntax:-  C:\> COPY CON <Filename>

C:\>COPY CON Rose.txt

A clock in a office can never get stolen

Too many employees watch it all the time

^Z

1 file(s) copied

After copy con we must specify a suitable file name. Press enter. Start typing the informations of the file. After gathering the information we press ^Z (CTRL+Z) button or F6 button to save the file. After pressing enter key computer will show a message like 1 file(s) copied. This means that file is stored in the disk. Suppose we don't want to save the file or we just want to abort from file creation job, then we simply press ^C (CTRL+C) button to abort without saving the file, intend of pressing ^Z button.

Notes:-  1. Never forget to give a suitable filename

              2. You can use extension as .TXT for denoting the file as Text file.

8. TYPE:- This command is used to display the contents or text of any file to the display device.

Syntax:- C:\> TYPE <Filename>

A:\>TYPE GULAB.TXT

A clock in a office can never get stolen

Too many employees watch it all the time

9. COPY :-  Copy command is used for copy any file to another location or to copy the files to another directory. This command may also be used for copying any file to another disk with different file name.

Syntax:-  C:\> COPY <Source filename> <Target file name>

 C:\>COPY ROSE.TXT ROSE.MSG

         1 file(s) copied

TO copy a file from hard disk to floppy disk

C:\>COPY Rose.txt A:

      1 file(s) copied

To copy a file from Floppy Disk to Hard disk

A:\>COPY LOTUS.TXT C:\

1 file(s) copied

10. REN:- (Rename) This command is used to change the name of any file or directory.

Syntax:- C:\> REN <Source filename> <Target filename>

C:\>REN ROSE.TXT GULBAL.TXT

If we get successfully C:\ that means filename or directory name is get changed. Either it will show the error message.

To changing the filename present in floppy disk

C:\>REN A:\ROSE.TXT GULAB.TXT

Note that you cannot specify a new drive or path for your destination.

11. DEL:- This command is used for erasing any file from the disk.

Syntax:- C:\> DEL <Filename>

C:\>DEL LOTUS.TXT

If it successfully erase the file from dosk then C:\> prompt will be appear, either computer will show an error message.

Note:- /P option is used for permission before deleting the file.

Directory related commands

12. MD:- (Make Directory)- This command allows to create a new directory. 

Syntax:- C:\> MD <Dirname>

C:\> MD REPORT

C:\>

Now this directory can be used for keeping various sort of reports. Under this directory we can create another directory which is known as subdirectory.

13. CD:- (Change Directory):- We can enter or exit from any directory using this command.

Syntax:- To access any directory

C:\> CD <Directory name>

C:\> CD REPORT

C:\REPORT>

Prompt will change with the directory name. If we keep two dots after CD command than we will exit from the directory.

Syntax:-C:\> CD..

C:\REPORT> CD..

C:\>

14. RD:-(Remove directory):- This command is used when we want to remove any unusable directory form our disk.

Syntax:- C:\> RD <Directory name>

C:\> RD REPORT

15. PATH:- This command is used for display or sets directories for executable files.

Synatx:- C:\> PATH 

This command display current path settings.

C:\> PATH=C:\WINDOWS\COMMAND;C:\WINDOWS\;C:\TC

this command will sets the directories windows, the command subfolder of windows and TC folder for executable files. Operating system will look for executable files in these directories.

NOTE:- If we need any help for above DOS commands the we put a '/?' symbol after writting the command at DOS prompt .

     Example:- C:\> DIR/?  or  C:\> COPY/?

Introduction to MS-DOS

Ms-Dos stands stands for Microsoft Disk Operating System. Ms- DOS is an operating system. An operating system is collection of system programs, used for controlling input/output operation. It is also known as interface between hardware and user. A operating system may be considered as the language translator  which converts the users readable codes into machine readable codes, means machine level language or binary digits. 

When we start MS-DOS, we get a symbol on the screen like this

C:\>

This symbol is known as C drive or C-prompt. similarly A:\> is called A-prompt or A drive. Generally A:\ is used as floppy drive i.e. when we are working on floppy disk and C:\ is used for local disk or hard disk. A small blinking bar we see on the screen. This is cursor. It is waiting for your instruction. There few predefined words for DOS. These are known as DOS-Commands. Our operating system can understand only these predefined commands.

These DOS-Commands are divided into two parts.

Internal Commands

External Commands

Before we go on detail in these commands, let first we understand a term called File and Directory. A file may be known as container of information on a particular topic. A directory may be considered as a structure or a cabinet which keeps one or more files. Directories are usually creates for keeping one or more identical files together.  Every file have a filename which helps to recognize them. these are divided into two parts

File name or Primary name

Extension or Secondary name

The primary name can be from 1 to 8 characters long. The extension contains 1 to 3 characters long. A filename and extension are separated by using a dot symbol. Thus it's structure looks like

Filename        .        Extension

Primary name .        Secondary Name  

The valid characters for giving a file name are form A to Z and the digits are form 0 to 9. Special symbols are ~ ^ % # @ ! _ - { } [ ] ' `.

Extensions or secondary names are usually used for denoting the type of files or the type of informations stored in the file. Like the filename have extension EXE, BAT, COM are respectively Executable, Batch and Command files, which are given high priority by DOS. Because these files could be directly understand by operating system. Similarly the filename having extension BMP, GIF, JPEG etc. are the extension for graphical files. The files having extension C or CPP are the files of C/C++ language, BAS for BASIC language, PAS for PASCAL programming and so on.