EXTERNAL-COMMANDS.ppt EXTERNAL-COMMANDS.ppt

External Commands
 Are stored in some external files which are stored
on some secondary storage device.
 Whenever an external command is executed then
the external file in which that particular
command is stored in transferred from disk to
main memory i.e. RAM
 All executable files with extensions .com, .exe
and .bat are the external commands.

Where the DOS external files
resides?
C:> cdWINDOWS
C:>WINDOWS> CD COMMAND
C:>WINDOWS> COMMAND> dir
InWindows7
C:> cdWINDOWS
C:>WINDOWS> CD SYSTEM32
C:>WINDOWS> SYSTEM32 > dir

ATTRIB
 Change or view the attributes of one or more files.
 Stored in ATTRIB.EXE file which is needed for its
execution.
 Syntax:
ATTRIB [+R|-R] [+A|-A] [+S|-S] [+H|-H][drive:][path][filename] [/S [/D]]
 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
• /D - Process folders as well.
• /S - Process matching files in the current folder and all subfolders.

ATTRIB: EXAMPLES
 C:>attrib
Shows the current attributes of all the files
present at C drive.
 C:>attrib abc +H
hides the abc file.
 C:>test +H +R
hides and make the test file read only.

LABEL
 Requires LABEL.EXE file for its execution.
 Label is used to view or change the label of the
computer disk drives.
 Syntax:
LABEL [drive:][label]
 Example:
C:>label a: mydisk
This would label the disk currently in the drive to
"mydisk“.

BACKUP
 External command that requires BACKUP.EXE
for executing this command.
 Enables users to backup their data on their
computer.
 Syntax:
BACKUP [Source:PathFilename] [Target:] [/s]
[/m] [/a] [/d:date] [/t:time] [/f:size]
[/L:LogDrive:PathLog]

BACKUP OPTIONS
/A Does not erase the files on the target disk .
/F:(size) Formats the target disk (if it is not already formatted).
/L Makes an entry in the backup log in the file you specify here.
/M Only backs up files that have been modified since the last time the
BACKUP command was used.
/S Causes files in the specified directory and all subdirectories below the
specified directory to be backed up.
/D:(date) Backs up files only if they have been created or modified on or after the
date you enter.
/T:(time) Backs up files only if they have been created or modified on or after the
time you enter.

BACKUP: Examples
 C:>backup C:TC F:/S
Copies all the files with all subdirectories of the
TC directory to drive F.
 C:>backup c:letterssale*.* a:
All files in the drive C LETTERS directory that
begin with SALE and with any filename
extension are backed up onto the disk in drive A.

CHKDSK
 Requires CHKDSK.EXE file for execution.
 Chkdsk is a utility that checks the computer's hard
disk drives' status for any cross-linked or any
additional errors with the hard disk drive.
 Syntax:
CHKDSK [drive:][[path]filename] [/F] [/V]

CHKDSK Options
/F Fixes errors on the disk.
/V Displays the full path and name of every file
on the disk

CHKDSK: Examples
 C:>chkdsk
checks the current drive.
 C:>chkdsk a:
checks the drive a.

FORMAT
 Requires an external file FORMAT.COM.
 Used to make a disk usable for OS by dividing the
disk into magnetic tracks and sectors.
 Syntax:
FORMAT drive:/switches

FORMAT Options
/V[:label] Specifies the volume label.
/Q Performs a quick format.
/F:size Specifies the size of the floppy disk to format (such as 160,
180, 320, 360, 720, 1.2, 1.44).
/B Allocates space on the formatted disk for system files.
/S Copies system files to the formatted disk.
/T:tracks Specifies the number of tracks per disk side.
/N:sectors Specifies the number of sectors per track.
/1 Formats a single side of a floppy disk.
/8 Formats eight sectors per track.
/C Tests clusters that are currently marked "bad."

FORMAT: Examples
 C:>format A:
formats a disk A.
 C:>format A:/3
formats 31/2 inch floppy disk.

MOVE
 Executed when a file MOVE.EXE is loaded in
RAM.
 Used to move one or more files.
 Analogous to cut and paste.
 Syntax:
MOVE <source> <destination>

MOVE Options
/Y Suppresses prompting to confirm you want to overwrite
an existing destination file.
/-Y Causes prompting to confirm you want to overwrite an
existing destination file.

MOVE: Examples
 C:>move c:windowstemp*.* c:temp
Moves the files of c:windowstemp to the temp
directory in root, this is of course assuming you
have the windowstemp directory.
 C:>move abc test
renames the abc directory to test.

TREE
 Displays all the directories and subdirectories
graphically.
 Syntax
TREE <path> /switches
 Options
/F Includes the file names in each subdirectory.
/A Displays the subdirectory using standardASCII characters
rather than graphic characters .

DELTREE
 Requires external file DELTREE.EXE for its
execution.
 Deletes a directory and all the subdirectories
and files in it.
 Syntax:
DELTREE [/Y] [drive:]path [[drive:]path[...]]

DELTREE: Examples
 C:>deltree c:fake010
Deletes the fake010 directory and everything
in it.
 C:>deltree D:test*.*
Deletes all the files in test directory present
on drive D.

FIND
 Requires an external file FIND.EXE.
 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.
 Syntax
find "keyword" <filename>
Searches for a text string in a file or files.

Find Options
/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.

FIND: Examples
 C:>find “this” def.txt
searches the string this in the def.txt file.
 C:>find “this” def.txt/c
displays the count of lines in def.txt file that contain string this.
 C:>find “this” def.txt/n
Displays the line number which contains this as a string in
def.txt.
 C:>dir|find def
Displays whether the file def is there in the current path or not.

RESTORE
 Used to restore files from disks made using the
BACKUP command.
 Syntax:
RESTORE sourcedrive: targetdrive: [path][/switches]

Restore Options
/P The program prompts you before it restores files that have been
changed since the last backup or files that are marked read-only.
/S Backed up files from both the specified source directory and from
subdirectories within that directory are transferred to the target
path designation
/B:mm-dd-yy Only restores files that were modified on or BEFORE the date you
enter.
/A :mm-dd-yy Only restores files that were modified on or AFTER the date you
enter.
/E Only restores files that were modified at or EARLIER than the time
you enter.
/L Only restores files that were modified at or LATER than the given
time.
/M Only restores files that have been modified since the last backup.
/N Only restores files that no longer exist on the destination disk.
/D Displays a list of the files on the backup disk that match the names
specified in filename without restoring any files

RESTORE: Example
 C:>restoreA: C:
restores files from the backup disk in drive A:
that originally resided on the currently logged
subdirectory.

SORT
 Sorts input and sends it to the screen or to a file.
 Syntax
SORT [/R][/+n] <filename>
 Options
/R Reverses the sort (sorts from Z to A).
/+n Starts sorting with column number (n) you
enter.

SORT: Examples
 C:>sort a:test d:abc
To sort the file test on drive A and send the output
to a new file abc on drive D.
 C:> sort /r a:phones.txt c:phone1
Sorts in reverse order (Z to A) the file PHONES.TXT
on drive A and send the output to a new file
PHONE1 on drive C.
 C:> sort /+3 > b:temp
Create a sorted fileTEMP, sorting on the character
in column three, by using input from the keyboard.

SYS
 Copies MS-DOS system files and command
interpreter to a disk you specify.
 Syntax:
SYS [drive1:][path] drive2:
 Example:
C:>sys a:
If you type this from c drive and you have a
formatted disk in the drive, this would copy the
system files to that disk making that disk bootable.

DISKCOMP
 Compares the contents of two disks on a track
by track basis.
 It checks whether two disks are identical or not.
 Compares only floppy disks that are of same
size.
 Syntax:
DISKCOMP <Source> <Target> /switches
 Options:
/1 Compares only the first side of the disks
/8 Compares the first 8 sectors per track.

SCANDISK
 Requires two external files SCANDISK.EXE and
SCANDISK.INI for execution.
 Disk analysis and repair tool used to check a
drive for errors and correct any problems that it
finds.
 Syntax
SCANDISK <drivename>/switches

SCANDISK Options
/all Used to check and repair all local drives.
/autofix This option will fix any errors it encounters without
prompting you first
/checkonly Use this option if you want to check a drive for errors
without repairing the damage.

DISKCOPY
 Requires an external file DISKCOPY.EXE for its
execution.
 Used to copy all the files as well as directories
from one disk to another on a track by track basis.
 Only copy floppy disks that are of the same size
and capacity.
 If target disk is unformatted, DISKCOPY will
automatically format the disk first automatically.
 Syntax
DISKCOPY [drive1: [drive2:]]/switches

DISKCOPY Options
/1 Copies only the first side of the diskette, even if the target
diskette is double sided.
/V Verifies that the source data was copied correctly onto the
destination drive. Selecting this option will slow down the
copying process.
/M Make use of RAM to speed up copy access.

DISKCOPY Examples
 DISKCOPY a: b:
Copies the contents of the disk in drive A to the
disk in drive B (erasing any data already on the
disk).
 DISKCOPY a: a:
If there is only one floppy drive then DOS first
reads the source floppy disk and then prompts
you to remove the disks and insert the target
disk.

XCOPY
 Requires an external file XCOPY.EXE
 Copy entire directory trees.
 Xcopy is a version of the copy command that can
move files and directories from one location to
another.
 Syntax:
xcopy <source_dir> <destination_dir>

XCOPY Options
/A Copies only files with the archive attribute set, doesn't
change the attribute.
/M Copies only files with the archive attribute set, turns off the
archive attribute.
/D:m-d-y Copies files changed on or after the specified date. If no
date is given, copies only those files whose source time is
newer than the destination time.
/P Prompts you before creating each destination file.
/S Copies directories and subdirectories except empty ones.
/E Copies directories and subdirectories, including empty
ones. Same as /S /E. May be used to modify /T.

XCOPY Options
/V Verifies each new file.
/W Prompts you to press a key before copying.
/C Continues copying even if errors occur.
/I If destination does not exist and copying more than one file,
assumes that destination must be a directory.
/Q Does not display file names while copying.
/F Displays full source and destination file names while copying.
/L Displays files that would be copied.
/H Copies hidden and system files also.
/R Overwrites read-only files.
/T Creates directory structure, but does not copy files. Does not
include empty directories or subdirectories. /T /E includes
empty directories and subdirectories.

XCOPY: Examples
 C:>XCOPY abc*.txt D:
copies all files in the abc directory with the
extension .txt to drive D:
 C:> xcopy c: a: /s
Copies all files and directories (except empty
directories) from drive C to drive A.

DOSKEY
 MS-DOS utility that allows a user to keep a
history of commands used on the computer.
 Before using it, it is required to install doskey by
writing this command on the DOS prompt.
 Syntax
doskey/options

DOSKEY Options
/HISTORY Displays all commands stored in memory
/LINE: size Sets maximum size of line edit buffer(default:128)
/OVERSTRIKE Overwrites new characters onto line when typing(default)
/REINSTALL Installs a new copy of DOSKey
UP,DOWN arrows recall commands
Esc clears current command
F7 displays command history
Alt+F7 clears command history
[chars]F8 searches for command beginning with [chars]
F9 selects a command by number

DOSKEY Examples
 C:>doskey
installs doskey and allows you to press the up or
down command to see history, or right or left to
retype previous command.
 C:>doskey /H
Displays a list of all the commands currently
stored in memory.

DEFRAG
 Optimizes disk performance by reorganizing the
files on the disk.
 Syntax:
defrag Drive: /F /U /S:order /B /Skiphigh /LCD /BW /G0 /A /H

DEFRAG Options
Option Description
Drive: Drive letter that you wish to defragment.
/F Insures that no empty space remains between files.
/U Leaves empty space if any is found between files.
/LCD Start defrag in LCD color mode.
/BW Start defrag in black and white color mode
/G0 Disable mouse and character set
/A Start defrag in automatic mode.
/H Move hidden files.

DEFRAG Options
Option Description
/S Order/Sorts files in specific sort <order>.
N =Alphabetic name order.
-N= Reverse alphabetic name order.
E =In alphabetic file extension order.
-E =Reverse alphabetic file extension order.
D= In date order (earliest to latest).
-D= Reverse date order (old to new).
S =By file size (small to large)
-S =By file size (large to small)
/B Reboot computer after completing defrag

EDIT
 Requires an external file EDIT.COM for its
execution.
 Used to create a file, change or modify the
contents of an already existing file.
 A menu driven text editor.
 Syntax:
EDIT filename.extension [/switches]

EDIT Switches
/B Black and white display.
/H Alerts line display for current monitor.
/R Load file in read only mode.

Batch Files
 An ASCII text file containing a list of DOS
commands.
 A batch file can be given any valid DOS file name
having an extension .BAT
 Can be created by using COPYCON command.
COPY CON filename.BAT
OR
EDIT filename.BAT

Commands
Command Description
@ Does not echo back the text after the at symbol.This is most commonly
used as @ECHO OFF to prevent any of the commands in the batch file
from being displayed, just the information needed.
%1 The percent followed by a numeric value, beginning with one, allows
users to add variables within a batch file. For example,
ECHO Hello %1
When the above one-line batch file is created, add your name after the
batch file. For example, typing myname (being the name of the bat file)
and then your name:
myname bob
would output:
Hello bob
PAUSE Prompt the user to press any key to continue.

Commands
Command Description
:: One of two ways of adding remarks into the batch file without
displaying or executing that line when the batch file is run.
:LABEL By adding a colon in front of a word, such as LABEL, you create a
category, more commonly known as a label.This allows you to skip to
certain sections of a batch file such as the end of the batch file.Also
see GOTO.
CALL This is used to run another batch file within a batch file.When the
batch file that is called is completed, the remainder of the original
batch file is completed. Note if the batch file does not exist it will give
an error message.
CHOICE It allows to accept various user responses from a list of options.
CLS Just like the DOS command would clear your screen.

Commands
Command Description
ECHO Will echo a message in the batch file. Such as ECHO HelloWorld will
print HelloWorld on the screen when executed.
EXIT Exits out of the DOS window if the batch file is running from Windows.
GOTO
LABEL
Used to go to a certain label, such as LABEL.An example of GOTO
would be to GOTO END
IF Used to check for a certain condition if the condition exists. If that
condition exists it will perform that function
REM One of two ways of adding remarks into the batch file without
displaying or executing that line when the batch file is run.
SHIFT Changes the position of replaceable parameters in a batch program.

Simple Batch File
C: edit ex.bat
date
time
vol
dir/p
Save the contents.To execute write
C:>ex.bat

Use of ECHO
C: edit ex1.bat
date
pause
rem date command is executed.
echo ********************
echo
echo Hello Everyone
echo
echo *********************
rem finishesd

To Make and Change Directory
:: makes and changes to the specified directory
::
@echo off
Cls
MD %1
CD %1

To copy all or specified files from
the D drive to the current directory
::copies all or specified files from the
::D drive to the current directory
::
@echo off
echo
if "%1"=="" xcopy D:*.*
if not"%1"=="" xcopy D:%1
echo
dir

IF EXIST command sequence
:: Example of IF EXIST command sequence.
@ECHO OFF
IF EXIST %1 ECHO File %1 exists!

Pause Command
:: Example of the PAUSE command
:: and the ways to exit out of a program.
@ECHO OFF
ECHOThe next command is a PAUSE
ECHO Do NOT press Ctrl+C or Ctrl+Break
PAUSE
ECHO Press Ctrl+C or Ctrl+Break
PAUSE

Looping in Batch Files
:: A batch file example using a batch loop.
:TOP
DIR
GOTO TOP

Using variables
@echo off
set name=%1
set address=%2
set city=%3
echo My name is %name%
echo My address is %address%
echo My hometown is %city%

CONFIG.SYS
 CONFIG.SYS is an ASCII text file that contains
instructions to DOS regarding your system
configuration.
 Resides on the root directory of the default
starting drive and is read only once at the startup
time.

CONFIG.SYS Commands
 Buffer
 Specifies the size of the disk buffer. The disk buffer is
the reserved area of RAM for the disk read and write
operations.
 Syntax:
Buffer=##n
where ## represents numbers between 1-99 and n
represents read-ahead buffers which store data just
beyond the area of the disk being read.
 Example:
Buffer=20

CONFIG.SYS Commands
 Install
 Used to install some executable programs after starting
of the computer.
 This command speeds installation and minimizes
addressing problems.
 Example:
install=abcd.exe

CONFIG.SYS Commands
 Device
 Allows us to install any hardware device that is supported
by DOS.
 Helps to install the device drivers in your computer’s
memory.
 Syntax:
device=<filename>
 Example:
device=keyboard.sys

CONFIG.SYS Commands
 Files
 Used to set and specify the number of files that can be
opened simultaneously in DOS.
 By default, the number of files are 8 and the maximum
number that can be specified is 255.
 Example:
Files=20

CONFIG.SYS Commands
 Last Drive
 Used to tell how many drives are there in your computer.
 By default, the last drive assumed to be E.
 Syntax:
lastdrive=<drivename>
 Example:
lastdrive=F

CONFIG.SYS Commands
 Shell
 DOS contains a file COMMAND.COM which is root
directory of the hard disk. This command helps to
specify another location for COMMAND.COM.
 DOS
 Used to load the operating system in the
conventional, extended or reserved memory.

AUTOEXEC.BAT
 A special batch file that is executed
automatically when user boots the computer.
 Executed after CONFIG.SYS file.
 Can be used to set up the starting directory,
change system prompt, change date/time or
automatically start some program.

SET
 Displays, sets, or removesWindows
environment variables.
 Syntax:
SET [variable=[string]]
variable Specifies the environment-variable name.
string Specifies a series of characters to assign to
the variable.

1. The BIOS loads the boot code in the master
boot record and transfers control to it. The
master boot record code begins execution.
2. The master boot code examines the master
partition table. It is searching for two things.
 It must determine if there is an extended DOS
partition.
 It must determine if there is a bootable partition
specified in the partition table.

3. If the master boot code finds an extended
partition on the disk, it loads the extended
partition table that describes the first logical
volume in the extended partition. This
extended partition table is examined to see if
it points to another extended partition table.
If it does, then that table contains
information about the second logical volume
in the extended partition, so it is loaded and
examined. (Recall that logical volumes in the
extended partition have their extended

4. After loading the extended partition
information (if any), the code attempts to
boot the primary partition that is marked
active (bootable). If there are no partitions
marked active, then the boot process will
terminate with an error. The error message is
often the same one that occurs if the BIOS
finds no boot device, and is generally
something like "No boot device", but can be
the infamous "NO ROM BASIC - SYSTEM
HALTED".

5.If there is a primary partition marked active,
the code will boot it. The rest of the steps
assume this is a DOS primary partition.
6. The volume boot sector is loaded into
memory and tested, and the boot code that it
contains is given control of the remainder of
the boot process.

7. The volume boot code examines the
structures on the disk that it is booting to
ensure that everything is correct and in the
right place. If not, the boot process will end in
an error here as well.
8. The code searches the root directory of the
device being booted for the operating system
files that contain the operating system. For a
system running MS-DOS these are the files
"IO.SYS", "MSDOS.SYS" and
"COMMAND.COM".

9. If the operating system files are not found,
the boot program will display an error
message, which is usually something like
"Non-system disk or disk error - Replace and
press any key when ready". Some people
think that this message means the system
was never booted, that the BIOS examined
the floppy disk for example and just rejected
it because it couldn't boot it. As you can see
from this description of the boot process, the
volume boot code was indeed loaded and

10. If the operating system files are found, the
boot program will load them into memory
and transfer control to them. First, IO.SYS is
loaded and its code executed. IO.SYS will
then executed MSDOS.SYS (in pure DOS
systems--MSDOS.SYS is just a text file in
Windows 95 and later.) Then the more
complete operating system code loads and
initializes the rest of the operating system
structures. For MS-DOS, this means loading
the command interpreter (COMMAND.COM)

EXTERNAL-COMMANDS.ppt EXTERNAL-COMMANDS.ppt

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