Types of External Commands in MS-DOS

1.  attrib

Change or view the attributes of one or more files. It defaults to displaying the attributes of all files in the current directory.

   Options:

• To add an attribute attach a '+' in front of it.
• To remove an attribute attach a '-' in front of it
• Attributes include
• R - Read-only
• A - Archive
• S - System
• H – Hidden

Syntax:

C:\>attrib [+|-ahrs] [file spec]

Directory Attrib Functions: It is also possible to use ATTRIB across directories.

[drive:][path][file name]

Specifies a file or files for attrib to process.

• /D - Process folders as well.
• /S - Process matching files in the current folder and all subfolders.

2. backup and restore

Programs to back up and restore files from an external disk. These appeared in version 2, and continued to PC-DOS 5 and MS-DOS 6 (PC-DOS 7 had a diversion check).

In DOS 6, these were replaced by commercial programs (CPBACKUP, MSBACKUP), which allowed files to be restored to different locations.

3. chkdsk

Verifies a storage volume (hard disk, partition, floppy disk, flash drive, etc) for file system integrity.

Options:

• /F : Fixes errors on the volume (without /F , chkdsk only detects errors)
• /P : Forces a full verification
• /R : Searches for defective sectors and recovers legible information (applies /F)
• /X: Unmounts the volume before processing if needed. (Note: An mounting temporarily invalidates all pointers/handlers to the volume until process is completed)

Syntax:

C:\>chkdsk volume letter: [[path]file name] [/F]   [/P] [/R] [/X]

4. defrag

        Defragments a disk drive.

Options:

·         -A – Analyses the fragmentation of a disk drive

·         -F – Force defragmentation even if disk space is low

·         -V – Verbose output mode

·         -H – Defrag hidden files

Example of usage:

         Defrag drive letter: -a -v

5. deltree

Deletes a directory along with all of the files and subdirectories that it contains. Normally, it will ask for confirmation of such a drastic action.

        Deltree [/y] directory

The /y parameter, if present, tells the deltree command to carry out without first prompting for confirmation.

The deltree command is not included in recent Microsoft Windows operating systems. Deleting a non-empty directory in those versions of Windows where the command is not included can be achieved by using the rmdir command as in the following example:

Rmdir /s [/q] directory

6.edit

Full-screen text editor, introduced in MS-DOS

Sntax:

C:\>Edit  filename

7. fc or comp

Compares two files or sets of files and displays the differences between them.

FC [/A] [/C] [/L] [/LBn] [/N] [/T] [/W] [/nnnn] [drive1:][path1]filename1 [drive2:][path2]filename2

FC /B [drive1:][path1]filename1 [drive2:][path2]filename2

/A        Displays only first and last lines for each set of differences.

/B        Performs a binary comparison.

/C        Disregards the case of letters.

/L        Compares files as ASCII text.

/LBn   Sets the maximum consecutive mismatches to the specified number of lines.

/N        Displays the line numbers on an ASCII comparison.

/T        Does not expand tabs to spaces.

/W       Compresses white space (tabs and spaces) for comparison.

/nnnn Specifies the number of consecutive lines that must match after a mismatch.

[drive1:][path1] filename1      Specifies the first file or set of files to compare.

[drive2:][path2] filename2      Specifies the second file or set of files to compare.

.

8. fdisk

Manipulates hard disk partition tables. The name derives from IBM's habit of calling hard drives fixed disks. When run from the command line, it displays a menu of various partitioning operations:

1. Create DOS partition or Logical DOS Drive

2. Set active partition

3. Delete partition or Logical DOS Drive

4. Display partition information

5. Change current fixed disk drive (only available if the computer has more than one hard drive)

FDISK /MBR installs a standard master boot record on the hard drive.

FDISK /MBR #: where # is other partition on system. Completes above command on indicated partition.

eg: "C:\FDISK /MBR D:" would install boot record on D:\ partition.

9.find

A filter to find lines in the input data stream that contain or don't contain a specified string and send these to the output data stream.

Find may also be used as a pipe.

Syntax:

C:\>find "keyword" < ''input filename'' > ''output filename''

Searches for a text string in a file or files.

FIND [/V] [/C] [/N] [/I] "string" [[drive:][path]filename[ ...]]

/V        Displays all lines NOT containing the specified string.

/C        Displays only the count of lines containing the string.

/N        Displays line numbers with the displayed lines.

/I        Ignores the case of characters when searching for the string.

"string"  Specifies the text string to find.

[drive:][path]filename Specifies a file or files to search.

10. format

Delete all the files on the disk and reformat it for MS-DOS

In most cases, this should only be used on floppy drives or other removable media. This command can potentially erase everything on a computer's hard disk.

/autotest and /backup are undocumented features. Both will format the drive without a confirmation prompt.

Syntax:

c:\>format [options] drive

c:\>fORMAT drive: [/V[:label]] [/Q] [/F:size] [/B | /S] [/C]

11. help

Gives help about DOS.

MS-DOS

Help 'command' would give help on a specific command. By itself, it lists the contents of DOSHELP.HLP. Help for a specific command invokes the command with the /? Option.

12. more

Pages through the output so that you can view more than one screen of text.

command | more

13. move

Moves files or renames directories.

Syntax:

C:\>move filename newname

C:\>move drive letter:\older drive letter:\newdir

Example of usage:

C:\>move c:\old c:\new

14. print

Adds a file in the print queue.

Options:

• /D device: Specifies the name of the print devices. Default value is LPT1
• /P filename : Add files in the print queue
• /T : Removes all files from the print queue
• /C filename : Removes a file from the print queue

This command was introduced in MS-DOS version 2. Before that there was no built-in support for background printing files. The user would usually use the copy command to copy files to LPT1.

15. scandisk

Disk diagnostic utility. Scandisk was a replacement for the chkdsk utility, starting with later versions of MS-DOS. Their primary advantage over chkdsk is that it is more reliable and has the ability to run a surface scan which finds and marks bad clusters on the disk. Chkdsk had surface scan and bad cluster detection functionality included, and was used again on Windows NT based operating systems.

16. sort

A filter to sort lines in the input data stream and send them to the output data stream.

C:\>sort < input filename > output filename

17. undelete

Restores file previously deleted with del. By default all recoverable files in the working directory are restored. The options are used to change this behavior. If the MS-DOS mirror TSR program is used, then deletion tracking files are created and can be used by undelete.

Syntax:

C:\>undelete [filespec] [/list|/all][/dos|/dt]

18. xcopy

Copy entire directory trees.

Xcopy is a powerful version of the copy command with additional features; has the capability of moving files, directories, and even whole drives from one location to another.

Syntax:

C:\>xcopy directory [destination-directory]

19. load fix

Loads a program above the first 64K of memory, and runs the program.

Syntax:

C:\> loadfix [drive:] [path]file name