22810837 Disk Operating System

Disk Operating System By Naman kumar navikunjan/1

Disk Operating System

Operating System is a set of programs that is extremely important to activate and Co-Ordinate the activities of various hardware resources like the processor and Input/Output devices. In other words, Operating System controls the movement of information on in the Computer.

ORAn operating System is a collection of programs that manage System is to provide a basic set of computer instructions to manage the flow of information in the computer. The operating System forms the communication interface between the computer hardware, application software programs and the user.

Computer Boot Process

PostBoot RecordDos Kernel

Device DriversConfig.sys

Command.comAutoexec.BatDos prompt

POST(Power - On Self Test)

Whenever we switch on a PC a program called POWER-ON SELF TEST (POST) is executed from the ROM-BIOS(BASIC INPUT OUTPUT SYSTEM).It checks the hardware of the PC step by step and if it finds any error the PC will halt with an error massage displayed on the screen. If it does not find any error, it will enable the PC for further operation.

ORThe POST(POWER- ON SELF TEST) is a firmware which is always present in ROM-

BIOS of any PC and whenever the PC is switched "ON" the first program which is executed is POST. Basically POST is a series of programs which checks all the logic on the motherboard which contains the CPU and all the support chips, the base memory on the motherboard as well as on the expansion card and all the I/O devices that are connected with the PC.

If the POST find any error or malfunctioning of the hardware, it has four different methods of indicating the error.

(a) Display error massage as error code.(b) Output the different tomes (short or long) at the speaker.(c) Output the check points on Port A of programmable peripheral interface

(PPI)(d) Display a detailed error message.

With the help of the above error indicating methods, it becomes easy to locate and rectify the error that occurs in a PC.

BOOT RECORDOnce the POST performs the job of checking the computer and its

attached devices, the control is then transferred to "BOOT RECORD". The main function of "BOOK RECORD" is to convey the following information which it requires to know to access information from disk.

1. The number of bytes per sector2. The number of sectors per cluster, per track, per disk3. The number of sides4. The total number of sectors on disk5. The maximum no. of entries that root area can hold


6. The most important part of Boot record is to find out whether the disk is bootable or not.

DOS KERNELFrom the boot record the control is then transferred to the most important phase called DOS KERNEL.. DOS KERNEL is made up of two special hidden system files namely IO.SYS and MSDOS.SYS. DOS kernel works in tandem with COMMAND.COM for interfacing the computer, the user and the programs.

IO.SYSIO.SYS provides the basic facilities for handling the input and output (I/O device)

such as keyboard and the display on your terminal screen.MSDOS.SYS

MSDOS.SYS is the control program that runs everything OR This is a program for Application program to use it contains special subprograms to make many commonly easy for programmer.

CONFIG.SYSThe CONFIG.SYS file is a text file that contains special commands. these commands configure your computer's hardware components. so that MS-DOS and applications can use them. When MS-DOS starts, it carries out the commands in the CONFIG.SYS file. Typically, the CONFIG.SYS file is located in the root directory of current drive.

COMMAND.COMAfter setting the computer to suit the user's needs, the control is then transferred to "user interface" or "command interpreter" or COMMAND.COM This lie gets loaded into memory and then takes up the role of "policeman", who is on constant vigil to help out people in trouble.

The command processor consists of four distinctly separate parts:-(1) A RESIDENT PORTION resides on memory immediately after

MSDOS.SYS & its data area. This portion contains the routines to process interrupts of

Critical error handling Control break handling

Terminate address.This includes displaying error messages and interpreting the reply Abort, Retry or lgnore. All the DOS error handling is done within this position of the command processor.

(2) AN INITIALIZATION PORTION follows the resident portion. This section contains the Autoexec file processor setup.

(3) THE TRANSIENT PORTION is loaded at the high end of memory which is command processor itself. It contains:-

All the internal command processors.The batch file process.

Produces the system prompt.Accepts the keyboard commands & causes it to be executed.

(4) THE LOADER PORTION loaded with a routine to load & execute external commands, i.e., files with the extension .COM and .EXE. This portion is at the highest end of memory and is invoked but the EXEC function called to load the program.

AUTOEXEC.BATAn AUTOEXEC.BAT file lets you to run programs automatically when you

start MS-DOS OR Some information you want to flash out when you start the computer.HOW TO (RE)BOOT COMPUTER

(A) Set CPU button to ON.(B) Press Reset Button.(C) Press "CTRL+ ALT+ DEL"

Guide lines for DOS command(1) You can type commands in uppercase or lowercase letter or a combination of both.


(2) Commands must be spelled correctly. Incorrectly spelled commands may result in a "Bad command or file name" message.

(3) A colon (:) must be included when specifying a drive letter.(4) Commands are usually followed by one or more parameter.(5) To abort a command, press control and c (CTRL+C) and Control and Break

(CTRL+BREAK) at the same time.(6) The DOS prompt consist of the default drive letter and the character ">" E.g.:-

C:\>(7) Commands start executing only after you press the ENTER key.

WILD CARD CHARACTERSThe wild card characters are used to restrict the scope of a DOS command to only those files which matches the pattern specified.There are two types of wild card :- "*" & "?"Where "*" can substitute a set of characters & "?" can only substitute a character at a particular position.

DOS COMMANDS

There are two types of DOS commands :-1. INTERNAL COMMANDS 2. EXTERNAL COMMANDS

1. INTERNAL COMMANDS :- Internal Commands are those commands which get transferred into computer's memory. For e.g.:- DIR, COPY etc.

2. EXTERNAL COMMANDS :- External Commands are those commands which don't get transferred into computer's memory. For e.g.:- XCOPY, FORMAT etc.

INTERNAL COMMANDS

DATEThis command is used to enter or change the date known to the system

Syntax : - DATE [mm/dd/yy ]Ex : - c:> DATE

TIMEThis command is used to enter or change the time known to the system.

Syntax : - TIME [ hh : mm:[ss[.xx]]]hh = 0 - 23mm = 0 - 59ss = 0 - 59xx = 0 - 99 (hundredths of a second)

Ex. : - C:\> TIME

CLSThis command is used to clear the screen.

Syntax : - CLSEx. : - C:\> CLS

VOLThis command is used to see the volume label of the specified drive.Syntax : - VOL [Drive name:]

Ex. : - C:\> VOL

VERThis command is used to see the MS - DOS version.

Syntax : - VEREx. : - C:\> VER


DIRThis command lists the files and the sub directories in a directory except the hidden system files.Syntax:- DIR[drive:] [path ] [file name [.ext]] [/p] [/w] [/A] [/s]Ex.:- C\> DIR ( display all files)

C:\> DIR NAME ( display only specified name)C:\> DIR/P (display pause wise)C:\> DIR/W (display width wise)C:\> DIR/A (display files with specified attributes )C:\> DIR/S (display all files in a directory and all subdirectory)C:\> DIR ABC.*( display all files having name ABC)C:\> DIR ?.*( display all files having file name one character)

MD ( MKDIR)This command is used to creates a directory in the specified disk.

Syntax :- MD [drive:] [path ] <directory name>Ex. :- C:\> MD RAJ

CD (CHDIR)This command changes the DOS current directory of the specified directory OR displays the working directory.

Syntax :- CD [drive:] [path] <directory name>Ex. :- C:\> CD RAJ

CD..This command puts in the parent directory to the working directory.

Ex. :- C:\> ABC\RAJ> CD..C:\>ABC>

CD\This command changes the current directory of the default drive to its root directory .

Ex.:- C:\ABC\RAJ> CD\ C:\>

RD (RMDIR)This command removes a directory from the specified disk.

Syntax :- RD [drive:][path] <directory name>Ex. :- C:\> RD RAJ

RESTRICTION:- Directory should be empty. Hidden system directories can't be removed.

RENThis command is used to changes the name of the file specified in the first

parameter to the name and extension given in the second parameter.Syntax :- REN[drive:] [path]<old file name>

<new file name>Ex. :- C:\> REN RAJ.BAT NISHA.BAT

DEL or ERASEThis command is used to delete or erase a specified file(s).

Syntax:-DEL [drive:] [path]<filename>[p]Ex.:- C:\>DEL RAJ.BAT C:\> DEL*.BAT(deleted all files having extension .BAT)C:\> DEL*.*/P

( /P option is used for confirmation before deleting each file.)


TYPEThis command displays the contents of a text file on the screen.Syntax:-TYPE [drive:] [path] <filename>

Ex.:- C:\> TYPE RAJ.BAT

C:\>TYPE RAJ.BAT >PRNNOTE :- If you wants to redirect the output a file, use filename instead of PRN.

COPYThis command is used to copies one or more files to another specified disks.

Syntax :- COPY [drive:] [path] <file name> [drive:] [path]<filename>

Ex. :- C:\> COPY RAJ.BAT NISHA .BAT

C:\> COPY RAJ .BAT+ NISHA .BAT JEETU.BAT C:\> COPY*.* A:

PATHThis command displays or sets a search path for executable files.

Syntax :- PATH [drive:] [path] ;[drive:] [path]Ex. :- C:\> PATH A\;C:\

NOTE:-Type PATH; to clear all search- path settings and direct MS-DOS to search only in the current directory.Type PATH without parameters to display the current path.

PROMPTThis command set a new MS-DOS prompt.

Syntax:- PROMPT "prompt string"Prompt can be made up of normal characters and the following special codes

$Q --> =(equal sign)$$ --> $ (dollar sign)$T --> Current time$D --> Current date$P --> Current drive and path $V--> MS-DOS version number$N -->Current drive $G --> > ( greater -then sign)$L --> < (less- than sign)

Type PROMPT without parameters to reset prompt to the default setting.

EXTERNAL COMMANDS

DOS KEYThis command is loads the DOSKEY program into memory. The DOSKEY program recalls MS- DOS commands and enables you to edit command lines.

Syntax :- DOSKEYEx :- C:\> DOSKEY

NOTE :- F7 key is used to display all command into the computer memory. F9 issued to select a line number. ALT+ F7 key is used to remove all the previous used command from its memory.

DELTREEThis command deletes a directory and all the files and subdirectories that are in it.

Syntax :- DELTREE [drive:] [path] <subdirectory name>or <file name>

Ex. :- C:\>DELTREE RAJ

MOVEThis command moves one or more files to the location specify . It can also be used to rename files and directories.

Syntax :- MOVE [drive:] [path] <source file> <target file>


Ex. :- C:\> MOVE RAJ. BAT NISHA.BAT

SCANDISKThis command detects, diagnoses and repairs disk errors. It can repair both our file system (FAT) and physical disk, i.e. cross linked files, lost clusters, surface flaws etc. This is more useful than CHKDSK command.

Syntax :- SCANDISK [drive name:]Ex :- C:\>SCANDISK A:

EDITThis command starts MS-DOS editor, a text editor you can use to creates and change ASCII text files.

Syntax :- EDIT [drive:] [path] <file name>Ex :- EDIT AUTOEXEC.BAT

NOTE:- After using this command we get following MENUS:-

FILE EDIT SEARCH OPTION HELP

If you want to activate menu for doing the various types of job we have to select first character of that menu with ALT key.

DISKCOPYThis command copies the contents of the diskette in the source drive to the diskette in the target diskette is unformatted, during the copy the disk is formatted.

Syntax :- DISKCOPY <source drive name:> <target drive name:>

Ex. :- C:\> DISKCOPY A: B:

DISKCOMPThis command is used to compares the contents of two floppy disks

Syntax :- DISKCOMP <source drive name:> <target drive name:>

Ex :- C:\> DISKCOMP A:B

XCOPYThis command copies files, directories and their subdirectories.

Syntax :- XCOPY [drive:] <file name> [/P] [/S] [/E]

Ex. :- C:\> XCOPY A *.*/S/EC:\> XCOPY A *.*/P

NOTE :- /S --> switches used to copies directories and lower level subdirectories unless they are empty.

/P --> switches prompts you before copying each file to you let confirm whether you want to create each target file.

/E--> switches copies any subdirectories even if they are empty.

FORMATThis command formats a specified desk. Formatting analyzes the entire desk for

any defective tracks. This command is also used to format all new desk before MS- DOS can use them.

Syntax :- FORMAT [drive:] [/S] [/4] [/U] [/Q] [/C]Ex. :- C:\> FORMAT A /S/C/U

NOTE:- /S--> This option is used to copy the operating system files. /4 --> This option is used to format a low density( DSDD) in a

high density (1.2 MB) drive. /U --> This option is used to unformatting unsave. /Q --> This option is used to quick formatting. /C --> This option is used to correct the bad clusters.


SYSThis command creates a startup desk by copying hidden MS-DOS system files and the MS-DOS command interpreter (COMMAND.COM) to the disk. Syntax :- SYS < drive name:>

Ex. :- C:\> SYS A:

LABELThis command creates, change or delete the volume identification label on a desk.

Syntax :- LABEL [drive:] [volume label]Ex :- C:\>LABEL A:AKSHAT

TREEThis command graphically displays the structure of a directory.

Syntax :- TREE [drive name:] <directory name> [/F]Ex :- C:\>TREE A : RAJ/F

NOTE:- /F option lists the full path of each directory and subdirectory on the specified drive.

ATTRIBThis command sets or resets the file attributes for a single file, for selected files in a directory or for all files in a directory level . It also display the attributes of a file.

Syntax :- ATTRIB [+R] [-R] [H][-H] [+A] [-A] [path] <file name>

Ex. :- ATTRIB +H RAJ.BATNOTE:- +H --> change specified file(s) to hidden.

-H --> makes hidden file(s) visible again.+R --> change specifies file(s) to read only.-R --> change specifies file(s) to write only.+A --> sets the archive attribute of a file.-A --> clear the archive bit of the specified file.

CHKDSKThis command is used to checks the status of a disk and displays a status report. Can also fix disk errors.

Syntax :- CHKDSK [drive:] [/F] [/V]Ex. :- C:\>CHKDSK A /F/V

NOTE :- /F --> This option direct CHKDSK to fix errors found in a directory of FAT (File Allocation Table)/V --> This option display the name of each file in every directory as a desk is checked.WARNING:- Do not use CHKDSK with the /F switch when you are running windows.

UNFORMATThis command is used to recover files from an accidental desk format.

Syntax :- UNFORMAT [drive name:]Ex :- C:\>UNFORMAT A:

UNDELETEThis command is used to restores files that where previously deleted by using the DEL command.

Syntax :- UNDELETE [[drive:] [path] file name] Ex. :- C:\> UNDELETE RAJ.BAT

MODEThis command sets operation modes for devices.

Syntax :- MODE nEx. :- C:\> MODE CO80

Where "n" specified one of the following values 40, 80, CO40, CO80, MONO.NOTE :- 40 --> indicate 40 characters per line.

80--> indicate 80 characters per line.


MONO --> specified a monochrome display adapter with a constant display width of 80 characters per line.

MOREThis command that reads data from the standard input device, sends one screen of data to the standard output device and then pause with the message ---MORE---

Syntax :- MORENOTE :- The MORE command will not work if the disk is full or write protected because to hold input information until it is displayed. This command viewing long files.

Ex. :- C:\> TYPE RAJ.BAT | MOREC:\> MORE <RAJ. BAT

When the screen is full, the message ---MORE--- appears on the bottom line, press any key to see the next screen.

FIND This command is used to searches a files, several files, or piped input for a string.

Syntax :- FIND [/V] [/C] [/N] [I] "string" [drive:] [path ] < file name>

Ex. :- C:\> FIND /C "TEXT" RAJ. BATNOTE:- /V Displays all lines NOT containing the specified string./C Displays only the count of lines containing the string, but does

not display the lines also./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. If a pathname is not specified, FIND searches the text typed at the prompt or piped from another command.

SORTSorts input and writes results to the screen, a file, or another device

SORT [/R] [/+n] [[drive1:][path1]filename1] [> [drive2:][path2]filename2] [command |]

SORT [/R] [/+n] [> [drive2:][path2]filename2]

/R Reverses the sort order; that is, sorts Z to A, then 9 to 0./+n Sorts the file according to characters in column n.[drive1:][path1]filename1 Specifies file(s) to be sorted[drive2:][path2]filename2 Specifies a file where the sorted input is to be stored.command Specifies a command whose output is to be sorted.

SETVERThis command causes DOS to supply a different version number to an

application. It updates a table of application that require DOS to provide an earlier version number. We must load this table into memory by including the Command :

DEVICE = SETVER.EXE in your CONFIG.SYS file. Syntax : SETVER <Drive:\path\application> <Version>

[/D or Delete] Example : C:\>SETVER OLDGAME.EXE 3.3 C:\>SETVER/D OLDGAME.EXE

BACKUPBoth MSBACKUP (Backup for DOS) and Backup for Windows are used to copy

your files to one or more backup diskettes for safekeeping. In this way, if you experience a disk drive failure or data error, you can restore your files from the backup media.


When we run backup first time, then we are prompted to perform a compatibility test. This ensures that Backup is setup properly for your computer.

RESTOREThis command restored files back to a fixed disk after they have been copied to

floppy disks using BACKUP. This command available from DOS versions 2.00 through 5.00. Later versions of DOS include its own restore utility. Windows also uses same command. Q. Write the commands to display and print the DOS files.Ans. Describe TYPE command to see file's content (With MORE command)

Print May be taken through ">PRN" with Type command. "PRINT", an external command can also be used to print a text file. To do so type the command in following way :-

PRINT <Filename>This command print from background. Also printing through "EDIT"

command may be explain.

Q. Describe the process of formatting of hard disk. What are the various formatting options available in MS-DOS.

Ans. Make/Get a fresh set of floppies/ CDs of those operating system, want to install in Hard Disk later. That floppy/Cd should contain FORMAT Command. However, FORMAT command may be applied from the same disk too, but later above disks required.

Then give the following command :-FORMAT/U/S C:

System prompts a warning about removing all data, Press "Y" and the formatting procedure starts. A counter appears as 1%, 2% ....100% and after 100% format completed. IF "/S" Option had been given then SYSTEM files will be transferred to Hard Disk. After it, system prompts for enter "Volumn Label". Either enter something upto 11 character or press enter for none and it will show a report about disk status, i.e. how many bytes the disk have, free bytes, used bytes by system files etc.

Various options available in MS-DOS for formating is :-/S - To transfer system file after formatting./U - To does not save any unformatted information/C - To check for bad cluster and if not repairable then mark it as bad

area, that operating system does not write anything there later./V:label - To tell about volume label after formatting.

Q. Describe the command that you will use to analyse the directories, files and the file Allocation Table (FAT) on the designated drive and the process of generating a disk and memory status report.

Ans. Scandisk command is used to analyse the directories, fiels and FAT etc. It is an utility software which was introduced in DOS 6.2. This utility detects, diagnoses, and repairs disk errors on both uncompressed and DoubleSpace compressed drives. Scandisk can repair both of our file system (File Allocation Table or FAT) and physical disk errors. Examples of file system errors are cross linked files and lost clusters. Physical disk errors include surface flaws. Scandisk also maintain a log of repairs, i.e. what it had done in his repairing process.

Whenever Scandisk finishes checking our drive's file system, it asks us if we want to perform a surface scan. Surface Scan takes lot of time depending upon the size and speed of processor. It can be used as follows :-


Syntax :- SCANDISK [drive name:]Ex :- C:\>SCANDISK A:

Q. Describe the DEFRAG command. Write the command that will fully defragment drive C and arrange files in alphabetical order.

Ans. File defragmentation occurs as files are read from and written back to your disk. Files are written randomly into available space. Therefore, part of a file may be written to one location on your disk. When another file is encountered on the disk the system searches for the next available space. This process continues until many of your files become fragmented, which slows down read and write operations. The DEFRAG program is used to collect the files back into contiguous disk sectors. This speeds up file access and therefore can noticeably improve program performance. With the introduction of DOS 6.2, DEFRAG makes use of extended memory. This feature enables DEFRAG to defragment larger disks containing many more files and directories.

Type simply DEFRAG at command prompt followed with drive name. A menu driven program appears from which we can select various options. To Defrag the files of Drive C: we have to do following thing.

C:\> DEFRAG C:Defragmentation starts. From the coming menu using TAB key goto Sort

option and choose Name radio buttom and press enter to start defragmenting. It is a good idea to use SCANDISK before DEFRAG command.

Q. Describe the command that will compare the contents of one file with the another file and displays the first ten differences between them.

Ans. COMP and FC commands are external DOS commands that compares the contents of two specified files. Both of these commands perform similar operations.

The most notable use of the COMP command is to compare one or more copies of a file to the original file to verify an exact reproduction. This is the quickest way to ensure a good quality file copy. If you suspect copy problems, you may wish to use COMP or FC each time you make a copy of a file just to be safe.

You can also use the COMP and FC commands to locate differences in ASCII text files. This lets you go directly to the area of change for a visual comparison.

Following is the function of FC command :-FC [/A] [/C] [/L] [/LBn] [/N] [/T] [/W] [/nnnn] [drive1:][path1]filename1

[drive2:][path2]filename2FC /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.

Q. What is the purpose of ECHO command in a batch file?Ans. This command is used to turns off or on all the commands to display on

screen after using it. We can use this command on command prompt and in a Batch file too.

At the command prompt when we type "ECHO OFF", then command prompt disappears from the screen. However we can give instructions through


DOS commands, but command prompt remain hidden. Again when we apply "ECHO ON", it appears.

In the Batch file when we use "ECHO OFF", then instructions after it does not show on screen, only their results are shown. We can also use it to show any message on screen as "ECHO <Message>" in batch file. To get a blank line in our batch file report we have to give "ECHO.".

In a batch file this command is used to show any message, creating menus etc.

Q. Describe the purpose of FDISK command in DOS.Ans. The FDISK command is an external DOS command that prepares a fixed

(or hard) disk for use. This command is available with DOS versions 2.00 and later. It is used to organize your fixed disk into partitions, which allocates disk space to separate usable areas.

Each partition is assigned a logical drive letter, like C, D and E when more than one partition is used on a single disk device. Because the maximum amount of disk space addressed by DOS versions released prior to 4.01 was 32 megabytes, it was necessary to be familiar with partitioning strategies offered b the FDISK command in order to organize disk drives having storage capacities in excess of the 32-megabyte barrier. Smaller disks are normally given a single DOS partition.

The FDISK command is used after your fixed disk has received a low-level format. Performing this procedure erases all stored data. Therefore, if your hard disk is already formatted, then use it carefully.

Partitions created with FDISK command is generally used to keep two or more operating system in each partition. Sometimes, people also make partition in disk to keep different types of data in different drives. So that when one partition standing any problem than another can be use. Suppose that operating system and application programs may be keep in Drive C and working data in Drive D. Songs or games may be keeep in Drive E and so on.

Q. How is MSBACKUP command an improvement over the BACKUP command?

Ans. BACKUP command is used with fixed disk systems using DOS versions 2.00 through 5.00. Later it changed into MSBACKUP command. BACKUP command was a charater based command in which a user remembered lot of switches but MSBACKUP command is a menu driven command, so now a user can select their choices from menu to take backup.

Backup is an external command used to copy files automatically from a fixed disk to floppy disks. BACKUP lets you copy selected files, all files in a specified directory or every file on the fixed disk. It also lets you copy only those files that have been changed or created from last backup. If the files being copied exceed the capacity of the target floppy disk, BACKUP prompts you to change disks and then to continue the process.

MSBACKUP if using, then first of all a compatibility test will be performed. The compatibility test is used to tell the Backup program about your system and user can configure the backup as per his requirement. Through MSBACKUP command a user can also verify backup data and compare the data with original data.

Q. Explain the purpose of the RECOVER command?Ans. The RECOVER command is an external command available on DOS

versions 2.00 and later. It is used to recover one or more files from a defective disk.

Assume that you are experiencing problems reading or copying a file named LETTER.TXT in drive B. You suspect data errors. You may be able to recover the file using the command RECOVER B:LETTER.TXT.

The bad data is often omitted by eliminating a bad disk sector from the file. If recovery is successful, you may be able to recreate the discarded data,


which is preferable to having to recreate an entire file. You should be aware that recovered files often have extra data at the end. This can be deleted using a standard ASCII word processors. Be sure to check the end of the file and eliminate any added "Garbage" as required.

Q. What is the function of SUBST command?Ans. The SUBST command was introduced in DOS versions 3.10. The command

word SUBST is an abbreviation for substitute. It is an external command that lets you assign a disk drive designator to a drive and file path of your choice. If you have a subdirectory designated as C:\DOS\UTIL, you can use SUBST to shorten this notation to a single disk drive letter. For example, the command

SUBST E: C:\DOS\UTIL returnE: => C:\DOS\UTIL

lets you use E: as a shorthand form for the notation "C:\DOS\UTIL". This shows you current substitution settings. You can see a file directory of C:\DOS\UTIL with DIR E:.

A substitution setting is disconnected with SUBST E:/D. This cancels the drive and/or pathname relationship associated with E:.

Q. Explain the Redirecting command Input and Output?The internal and external DOS commands normally take their input from the

keyboard (standard input device) and display their output on the screen (standard output device). However, you can instruct the DOS to accept input from a source other than the keyboard and send output to a destination other than the screen by redirecting and piping.

Redirecting InputTo accept input from a source other than the key board, a less-than symbol (<) is used. The symbol is placed just before the input source.eg : C:\> label < input.txt

Redirecting OutputTo send output to a destination other than the screen, enter a greater-than (>) in the command line. The symbol is placed just before the output destination. You can also redirect output of the DIR command to a file.eg : C:\> dir > Rajeev

C:\> dir > prn

Adding Output (Appending)If you want to add the new data to the end of an existing file, enter two greater-than symbols in the command line.eg : C:\> Dir/s >> Rajeev

Redirecting command Input and Outpureg : C:\> SORT < NAMES > LIST

This command sorts the contents of file "NAMES" alphabetically and stores it in a file named "LIST".

Q. How is MS-DOS Organised? Describe what is I/O system, the Command Processor and Utilities in MS-DOS.

Ans. MS-DOS is an operating system developed by Microsoft Corporation. MS-DOS is a large collection of different types of files among which minimum four files are compulsory for MS-DOS, i.e. IO.SYS, MSDOS.SYS, COMMAND.COM & DRVSPACE.BIN. Other files such as TREE.COM, EDIT.COM etc. are additional files which is necessory when we use External command of DOS.

IO.SYS, MSDOS.SYS, CONFIG.SYS, HIMEM.SYS, RAMDRIVE.SYS etc. are those files who control the Input and Output devices of computer, i.e. how a user instruct the computer and how the operating system control different part of the computer. Standard input and output devices are controlled by IO.SYS and MSDOS.SYS. Other


devices such as printer, scanner, mouse, CD-Drive etc. are controlled by there Device Drivers which is loaded through CONFIG.SYS or AUTOEXEC.BAT.

The DOS command processor or the command interpreter is contained in the COMMAND.COM program. This essential program controls the prompt, error messages, other messages, DOS environment etc.

Some utilities program such as FORMAT, SCANDISK, DEFRAG etc. are used to enhance the power of the Disk Operation System. These program is used to repair the disk and organise it so it can work fast.


Q. What are hierarchical directories? Illustrate a structure of a hierarchical directory.

Ans. We can store number of files on our disk. But if all the files will be stored on same location then searching a file will become much more lengthy. So, we keep all the files in some folders. These folders may also contain sub-folder and so on. These folders are used to keep related files together. System of storing files on disks, in

which files are stored in folders and folders can contain other folders are known as hierarchical directories. Following is the example of a hierarchical directory :-


Additional Knowledge of DOS

BATCH FILE Batch files are ASCII text files that store a series of commands that are later automatically executed line-by-line when you run the file. It’s Extension should always be .BAT. A batch file may include following elements :- DOS commands Program names Batch language commands Command line and environmental variables

Different commands used in a Batch file are :-1. @ - Turns off the display of command followed by @.2. Echo - Turns off or on all the commands to display on screen after using it.3. Pause - Prompts to strike any key to continue...4. Call <Filename> - Runs a second batch file and returns to the batch file from

which it was called.5. Goto <Label> - Used to transfer the control of program at any specific label.6. <:Labelname> - Label is used to give a specific name to a line of batch file.7. %0 - %9 - Lets you substitute from one to ten character strings in a batch file

command line. Suppose that we have created a file named REPORT.BAT :- C:\>COPY CON REPORT.BAT @ECHO OFF GOTO %1 :SALE TYPE SALE.TXT GOTO END :BUY TYPE BUY.TXT GOTO END :MARKET TYPE MARKET.TXT :END ^Z 1 File(s) Copied. C:\>REPORT <SALE> <BUY> <MARKET>

Now when we type any string followed with REPORT then %1 will be replaced with that string and then labeled set of command will be executed.

8. IF - This command is used to compare two different objects. These comparison may be of three types :- (a) Checking about existing of a file (b) Comparison between two words, whether they are equal or not (c) To know about ErrorLevel (A) IF [NOT] EXIST <FILENAME> COMMAND - This command checks the existance of a file and if returns True then execute command of the same line, otherwise control will be transferred to next line. @ECHO OFF IF EXIST %1 GOTO YES ECHO %1 FILE DOES NOT EXIST GOTO END :YES ECHO %1 FILE EXIST :END

(B) IF [NOT] <STRING1>==<STRING2> <COMMAND> - This command compares two text strings and execute same line’s command if the both is same, otherwise control will be transferred to next line. @ECHO OFF IF .%1 == .GOTO Errmsg


ECHO You have typed %1 GOTO end :Errmsg ECHO Please type a parameter :End Save this file with IFF.Bat. C:\> Iff abc.txt

This command line replace %1 with abc.txt, so .abc.txt will not be same as . (i.e. no any parameter), so condition become false and next line will be executed, i.e. “You have typed abc.txt”. C:\>Iff

This command line have no any second parameter, so now %1 will not have any value and .==. will become true so control will be transferred to :Errmsg and we will get “Please type a parameter”.

(C) IF [NOT] ERRORLEVEL == <EXITCODE> <COMMAND> - When we run any program then after completing its execution, it returns a code to OS, who tells OS that whether the program executed successfully or not. If any error had been appeared during the execution then what was it. DOS stored this code in a variable “ErrorLevel”. So, through this variable, if used with “IF” command, we can know about the error. Exit code Description 4 Lack of Memory 3 Fatal Error 2 Ctrl + C was pressed during the execution 1 Non Fatal Error 0 Program Executed successfully. @ECHO OFF XCOPY FF.BAT TEMP IF ERRORLEVEL 4 GOTO MEM IF ERRORLEVEL 3 GOTO DISKERR IF ERRORLEVEL 2 GOTO BREAK IF ERRORLEVEL 1 GOTO NON IF ERRORLEVEL 0 GOTO OK :OK PAUSE ECHO COPY COMPLETED GOTO END :NON PAUSE ECHO A NON FATAL ERROR APPEARED! GOTO END :BREAK PAUSE ECHO CTRL + C WAS PRESSED GOTO END :DISKERR PAUSE ECHO FATAL DISK ERROR APPEARED GOTO END :MEM PAUSE ECHO NOT ENOUGH MEMORY GOTO END :END ECHO BYE! 9. CHOICE - Waits for the user to choose one of a set of choices.

CHOICE [/C[:]choices] [/N] [/S] [/T[:]c,nn] [text] /C[:]choices Specifies allowable keys. Default is YN/N Do not display choices and ? at end of prompt string.


/S Treat choice keys as case sensitive./T[:]c,nn Default choice to c after nn secondstext Prompt string to display ERRORLEVEL is set to offset of key user presses in choices.

10. FOR - Runs a specified command for each file in a set of files.

FOR %variable IN (set) DO command [command-parameters]

%variable Specifies a replaceable parameter.(set) Specifies a set of one or more files. Wildcards may

be used.command Specifies the command to carry out for each file.command-parameters

Specifies parameters or switches for the specified command. To use the FOR command in a batch program, specify %%variable instead of %variable.

11. REM - This command is used to give comment line in batch file.Rem Developed by Rajeev Ranjan Kumar

CONFIG.SYS (SYSTEM CONFIGURATION COMMANDS)In order to make the computer system work efficiently, the DOS contains certain

system configuration commands. These are described below :1. FILES - Sets the maximum allowed number of simultaneously opened files. The

syntax is :FILES = n

The n parameter indicates the maximum number of concurrently open files. Default value is 8; maximum numbers is 255. If you exceed the maximum number of open files during processing, DOS displays the message "Too many files are open".

Example : FILES = 60

Each increment to this parameter decreases the amount of RAM available to application by 128 bytes. Therefore it serves no purpose to set this parameter any higher than the maximum possible number of files for our application.

2. BUFFERS - A buffer is an area of memory set aside for temporary data storage. Buffers can speed up system performance by reducing the number of times DOS must directly access the disk. However, each Buffer takes up about 530 bytes of RAM reducing the amount of memory available for processing. Too many buffers will slow down the system. Buffers command is used to sets the number of disk-read buffers.

Buffers = n (n may be 1 to 99)where n is the number of the buffers to be used by DOS.

3. COUNTRY - This command is used to start our system with a non United States keyboard and display character set.Syntax : COUNTRY = CODE, PAGE, DRIVE:\PATH\COUNTRY.SYSExample : COUNTRY = 044,, C:\DOS\COUNTRY.SYS

Where 044 is the code for united kingdom, second comma is used to use the default page and after it location of Country.Sys file is defined. Default country code is 001 of United State.

4. DEVICE - Different devices of our system requires some additional files to work properly. To do so we have to install and give accurate locations of that files and also it should be mentioned in booting process. DEVICE command is used to state the location of this type of file and because it is mentioned in CONFIG.SYS file, so automatically at the time of booting all the Device drivers are loaded.

Example : Device = C:\MOUSE\MOUSE.DRV

MS - DOS ERRORS


When an error is detected during reading or writing to any of the input or output device on your system MS-DOS displays an error message called DEVICE ERROR it may display some other massage but in case of Device Error, the system waits for you to respond.

If you know what caused the what caused the problem, take corrective action before choosing a respond.DEVICE ERRORS :- If a desk or device error at any time during a command or program, MS-DOS disk or device error occurs at any time during a command or program,MS-DOS displays an error massage in the following format :-Abort, Retry, IgnoreTo recover from an error condition, the respond should be made in the following order :-R --> Retry the operation because the error may not occur again. The system tries the read or write operation again.A --> Abort the program. The system terminates the program that requested the read or write operation.I --> Ignore the error condition and continue the program the system is unable to determine whether the condition is dangerous. Be careful when choosing this response the data may be lost.BAD COMMAND OR FILE NAME :-This error message is displayed when you issue an invalid command to the device specified in the error message. Check your command and make sure everything you are trying to do is supported.Data error:-This error message is displayed when MS-DOS is unable to read or write the data correctly due to a defective disk.Try choosing R(Retry) several times to retry the operation or choose A (Abort) to terminate the command. Make a new copy of the disk because if it's defective, your data may be lost.GENERAL FAILURE :- This error message is displayed when Diskette type and drive type do not match The disk is not completely inserted in the drive or the drive door is open. The diskette is not formatted properly.Check the disk is properly inserted or not. If you are using a new unformatted disk, format it.

NOT READY ERROR:-This error occurs when the device, usually a drive or printer, specified in the message is not ready to accept or transmit data for disk drives make sure that the diskette is formatted and the drive door is closed and then retry the operation. For printer assure that the printer is on, on -line, not busy and has sufficient paper, then retry the operation.

Sector not fond error :-This error usually means that the disk has a defective spot so that MS -DOS cannot find the requested information because the sector containing the data could not be located on the disk.

Either rerun the command with a different disk or copy all files from the disk onto a good disk and then try to reformat the defective disk.

Write fault error :-This error occurs when MS -DOS is unable to write the data to the specified device. Make sure the disk is properly inserted in the drive and choose R for Retry. If you get the same massage, choose A for Abort and rerun the command with a different disk.

Write protect error :-


This error occurs when you try to write data on a write- protected diskette. If the disk has a write protected tab, remove the tab before writing on the disk. If the disk dose not have a write - protected notch, you cannot write on that disk.

File allocation table bad :-This error occurs while reading or writing data on a faulty disk. possibly the disk was incorrectly formatted or not before use. If you get the same massage even after formatting the disk, the disk is unusable.

MS DOS MESSAGES

Abort edit ( Y/N)?This message is displayed when you specify Q command to quit the editing session without saving changes in EDLIN. Type a Y to end the edit or type a N to continue editing the file.Access denied This message is displaced when the specified command violates the access mode of the file, subdirectory, or device involved, e.g. If you try to write to a file marked read-only, or read a file that is write or open a subdirectory as a file.Are you sure (Y/N) ?MS-DOS displays this message when you try to delete all files in the working directory by using the *.* wildcard.

Type Y (for Yes) to delete all the files or N (for No) Attempted write - protect violation This message mean that the disk you are trying to format is write- protected.Bad command or file name MS- DOS displays this message when the command you just entered is not a valid DOS command.

Check the spelling of the command and re-enter it. If the command name is spelled correctly, check to see that the default drive contains the external command or batch file you are truing to execute.Bad or missing command interpreter.This massage is displayed when MS -DOS is unable to find the COMMAND.COM file on the disk; either the files is missing from the root directory, or the file is invalid, this message also appears if COMMAND.COM has been removed form the directory it was in originally when DOS was start to the CONFIG.SYS file contains any syntax error/invalid parameter.Either restart the system with a disk that contains the COMMAND.COM file or copy the COMMAND.COM file from your backup MS-DOS disk onto the disk used to start MS-DOS.Disk boot failure This message displayed when an error occurs while loading MS-DOS into memory.Restart the system. If this error persists, place a backup DOS diskette in drive X: and restart your system.Disk unsuitable for system diskMS- DOS displays this massage while formatting a diskette using /S parameter and the format command detects a bad track on the disk where the DOS files should reside. Use this disk to store data only.Error in .EXE fileThis message indicates that the .EXE file you have asked MS-DOS to load has an internal format.

You cannot run this program. Check to make sure you are using the correct version of MS-DOS. If you are using a program you wrote yourself, go through the LINK procedure again.File cannot be copied onto itselfThis massage is displayed when you try to copy a file, using COPY or XCOPY, and place the copy ( with the same name as the original) in the same directory and on the same drive as the original file. Change the name given to the copy, or put it in a different directory, or put in on another disk.


File creation errorThis message is displayed when you try to add a new file name or replace a file that already exists in the directory, or there was not enough space for the file. If the file already exists, it is read-only file and cannot be replaced. This error message may also occur if the root directory, or a hidden (or system) file.File not found This message is displayed when MS-DOS could not find the file that you specified on the command or command parameter.

Retry the command using the correct filename.Format another (Y/N)?FORMAT displays this message when it has finished formatting a disk . Type "Y" if you want to format another disk, or type "N" if you don't.Insert disk with \ COMMAND.COM in drive X:and strike any key when ready This massage indicates that MS-DOS is attempting or reload the command processor, but COMMAND.COM is mot in the drive that DOS was started from.

Insert the DOS diskette in the indicated drive and press any key.Insert DOS disk in drive X:and strike any key when ready This message means that you have typed the FORMAT command using /S parameter, so that FORMAT is trying to load the DOS files, but the indicated drive X: does not contains the DOS diskette.

Insert the DOS diskette in the drive specified and press any key.Insufficient disk spaceMS-DOS displays this message to indicate that the disk does not contain enough free to perform the specified operation.If you suspect this condition is invalid, run CHKDSK to determine the status of the disk, otherwise use another disk and retry the command.Invalid date This message indicates that you have entered an invalid date or delimiter. The only valid delimiters in a date entry are hyphens (-) and slashes(/). Re- enter a valid date.Invalid media or track O bad-disk unusable MS-DOS displays this errors message when the FORMAT command is unable to format track 0 on the specified media. This error occurs :-

Track 0 is unusable. track 0 is where the root record, File Allocation Table and directory must reside. If track 0 is bad, the disk is unusable.

The diskette type and drive type are incompatible. If you try to format a double - sided 320/360 KB diskette in a high - capacity, 1.2MB drive; or a high capacity 1.2MB diskette in a double sided 320/360KB drive.

In this case retry the format command specifying the /4 parameter.Invalid path, not directoryor directory not empty This massage is displayed while removing a subdirectory using RMDIR Command. This error occurs ifThe specified path is not a valid directory name. The directory you specified still contains entries for files or other subdirectories ( with the exception of the .and .. entries).

you can't remove a current directory. Chang to a different subdirectory and try again.Invalid path or file not foundMS-DOS display this message when you specify a wrong directory or file name with the command.Invalid time This message indicates that you have entered an invalid time or delimiter. Re-enter the correct time. The only delimiters are

Colon(:) between the hours & minutes Colon(:) between the minutes

Period(.) between the seconds and hundreds of a second.No path


The massage means that you have typed PATH and pressed the enter key to find out what search path is but did't set a command search path.Program too big to fit in memory MS-DOS displays this message when the file containing the external command can't be loaded because it is larger than the available free memory. It is possible that some programs you have run are still using some memory. Reduce the number in the BUFFERS= parameter in your CONFIG.SYS file, restart your system, and reissue the command. If the same message persists, your system does not have enough memory to execute the command.Syntax errorThis message indicate that the command format you have typed is incorrect. Check to make sure that you have typed the correct format of the command. System transferred This is an informational message telling you that the system files have been transferred during FORMAT(with /S parameter) or SYS Command processing.Unable to create directoryMS-DOS displays this message indicating that the directory you want to create Already exists. A file by that name already exists in that directory. The directory name you specified contains invalid characters or is a reserved device

name. You attempted to add a directory to the root directory and it is full.

Unrecognized command in config.sysMS-DOS displays this message if while starting up the system an invalid command was detected in the configuration file CONIG.SYS.

Correct the invalid command and restart DOS.

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