DOS Interview Questions and Answers

What is DOS?

DOS is an abbreviation for Disk Operating System and refers to the PC operating system. This operating system works as a medium between user and computer system, and between hardware and software too.

It is a character based, single user, single tasking, standalone operating system.

It can perform following task-
1) Management of Hardware and control devices such as keyboard, mouse, monitor, printer and scanner.
2) File system management for managing files and directories.
3) Memory management (storage device) and allocation of memory to various programs.
4) Management of the programs (kernel, UI and API) and their execution.

Many DOS options and / or enhancements are available, including MS-DOS (Microsoft Disk Operating System), FreeDOS and DR-DOS.

What is the DOS commands and explain the internal and external commands?

DOS commands are small programs and instructions that are made to perform a particular task. Every DOS command works differently. It is difficult to work on the computer without these commands. In DOS, there are many types of commands and they are classified into two types -

(1) Internal Commands
(2) External Commands

Internal Commands : These commands enter into computer memory during computer booting and are part of shell. There is no external file in the computer to read internal command.These commands are not in the form of any files, therefore neither they can be viewed nor can be edited or detected.
For example : DIR, MD, CD, TIME, DATE, COPY, COPY CON, TYPE etc.

External Commands : These are commands that are not in-built in DOS and are not part of shell, they are only loaded in memory when they are invoked. These commands are present in the form of files and mostly are in exe, bat and com extensions ,therefore they can be viewed, copied, changed or deleted.
For example : XCOPY, FORMAT, COPY, PRINT, SYS, EDIT, TREE, SORT, PROMPT etc.

Describe the 10 DOS commands?

The 10 DOS command are-

1) CD/CHDIR (Change Directory) command is used to displays or change directories in DOS. CHDIR is the alternative name of CD command.
examples
cd
cd ..
cd c:windows

2) CLS (CLRSCR) command is used to clear the contents of the terminal screen or console.
examples
cls

3) COPY command is used to copy complete file from one location to another. It is also used to make copies of existing files.
examples
copy test.bat c:windows
copy *.txt c:

4) DATE command is used to display the system date and prompts the user to enter a new date.
examples
date
date /t

5) DEL (ERASE) command is used to permanently delete one or more files from the computer.
examples
del test.txt
del *.txt
del *

6) DIR The dir command provides a list of available files in the current and or parent directory.
examples
dir
dir /p
dir /a
dir d*

7) EDIT is a full-screen text editor, which is used to view, create and modify text files.
examples
edit myfile.txt

8) HELP command provides help about DOS commands.
examples
help
help dir
help date
date /?

9) MOVE command is used to move one or more files or directories from one location to another. It also used to renames the files or directories.
examples
move test.txt d:win
move d* d:win
move test.txt d: ewtest.txt

10) REN command is used to rename files and directories from the original name to a new name. unlike the move command, this command can not be used to rename subdirectories, or rename files across drives and can not specify a new drive or path for the destination of the renamed file.
examples
ren *.txt *.doc
ren test.txt newtest.txt

Tell about networking related DOS commands?

ARP command is used to display and modify the Address Resolution Protocol(ARP) cache, which is a simple mapping of IP addresses to MAC addresses.
ARP is also useful when diagnosing duplicate IP assignment problems.
examples
arp -a

FINGER command allows you to view information about users logged onto a remote computer, that may include their email address, full name, when last time user logged in and read their e-mail etc.
examples
finger -l user@localhost

HOSTNAME command displays the name of the current host.
examples
hostname

IPCONFIG command allow you to configure network interfaces and view information about them.This command can be used to verify a network connection as well as to verify your network settings.
examples
ipconfig
ipconfig /all

PATHPING command utility enables a user to find network latency and network loss. Also that provides useful information about network latency and network loss at intermediate hops between a source address and a destination address.
examples
pathping www.microsoft.com

PING command is one of the most commonly used and known command. It allows the user to ping another IP address or computer/host name. It can help to determine whether the network is able to communicate with the network or not.
examples
ping www.google.com
ping -a 74.125.24.104

NBTSTAT command displays protocol statistics and current TCP/IP connections.
examples
nbtstat -a www.webiwip.com

NET command is used to manage, set, view and determine network settings.
examples
net view
net config

NETSTAT command is used to display the TCP/IP network protocol statistics and information.
examples
netstat
netstat -a

NSLOOKUP command enables a user to look up an IP address of a domain or host on the network.
examples
nslookup www.facebook.com

ROUTE command enables to view and modify the IP route table of the computer.
examples
route print

TRACERT / TRACEROUTE command helps determine network related issues or slowdowns. It is similar to ping command but can provides details of how a network packet travels and whether it may fail or slow down. It can help to determine the computer, router, switch or other network device which probably causes your network issues.
examples
tracert -d www.google.com

What is a batch file, give an example?

Batch files are special files with extension bat or cmd, which are often called scripts file that allows us to automate the task. Batch files contains a list of commands that are always executed together and in sequence, because we run the batch file as "command" instead of running each command individually.

We can create a batch file by using any text editor like the Notepad and by entering some lines of commands, and to save the file with an extension BAT or CMD.
To Run a batch file it require double clicking on it and it can also be run via command prompt or the windows start-Run line.

Example
Open the new text file and enter the following text in it and saved the file as "mybat.bat"-

@ECHO ON
REM This is an example of BAT file output.
@ECHO OFF
REM what we have...
Dir


This batch file contains two remarks i.e. "REM" which are used to provide notes or message by either the author or for the user of the file. Everything wrriten between the @ECHO On and off commands is displayed on the screen during the script's execution. After the second remarks/REM, there is a simple DOS "Dir" command which provide the lists the contents of the current directory.

Note that the individual commands or comments are separated by newlines which runs sequentially after double clicking on mybat.bat batch file.

How to run a Batch File?

A batch file can be run in two ways-

By command prompt as command
Double-clicking on the batch file

What is the difference between copy and copy con in DOS?

Copy is used to make a copy of a file, with this command, we can copy or append files with the same name or a new name in the current directory or any other location.
Examples-
copy a.txt b.txt
copy a.txt c.txt
copy a.txt+b.txt c.txt
copy c.txt d:

Copy con is also called copy console, it is used to write file. We can not use copy con to edit the file. After write in the file, CTRL Z is required to save and exit .
Examples-
copy con do.bat

@echo off
cls
echo This batch file does absolutly
echo nothing but print this line.
^z

CTRL Z ends the "writing" of the file.

What is chkdsk command?

Chkdsk is an abbreviation for check disk, used to check the status of the file system.

It scans the disk drive and helps in detecting error, repair and retrieval of data from bad sectors.

Examples
chkdsk
chkdsk d: / r
chkdsk d: / f
chkdsk *. *

What is AUTOEXEC.BAT file?

Autoexec.bat (Automatic execute batch) is a special plain-text batch file that is executed after system boot.
with this help, we can run commands, programs and batch files automatically at the time of startup or booting of the system, by adding them to this file.

Which is wild card character in DOS?

Wildcards are special characters and symbols that represent one or more characters. Commonly used wildcards are asterisk (*) and question mark (?).

An asterisk (*) is represents one or more characters, and a question mark (?) is represents a single character.

What is the xcopy command in dos?

The XCOPY command is used to copy one or more files and directories, including subdirectories from one location to another location.

Examples
xcopy c: est d: est /i
xcopy c: est d:

What is CONFIG.SYS?

Config.sys is a configuration file and it is executed during system boot.

It contains commands and instructions to load device drivers, lastdrive, shell, devicehigh, buffers etc. It also used to load programs in memory to manage memory,hardware, keyboard, mouse, printer, and other peripherals.

Config.sys is editable text file and it can be edit in any text-editing program.

After executing the command of the config.sys file, the autoexec.bat file is executed.

Latest Updates

General Knowledge of India

In 1897, the Birsa Movement supporters raised which colour flag as a symbol of Birsa Raj?

Ratio and Proportion

The cost of 10 books is Rs. 80/-. Find the value of 15 books?

The cost of 48 bags of paddy is Rs. 16,800/-. What is the cost of 36 bags of paddy?

Monthly expenditure of a family of 4 members is Rs 2800/-. What is the expenditure if there are 3 members in the family?

Annual incomes of the families of Sita and Latha are in the ratio 4:3 and their annual expenditure are in the ratio 3:2. What is their annual income if they save Rs. 3000/- in a year?

A certain sum of money is divided between A and B in the ratio of 5/4 : 5/3 and A got Rs. 360/-. Find the total sum of money and B’s share?

In an office, the ratio of the salaries of an officer and a clerk is 15:7. If the salary of a clerk is Rs. 720/- less than the salary of the officer, find the salary of each?

In an election to a municipal council, the votes secured by two candidates are in the ratio 13:19. The elected candidates gets 312 votes more than the second candidate. How many votes are secured by the second candidate?

A certain sum of money is divided between Murthy and Prasad in the ratio 22/7 : 8/3. If Murthy gets Rs. 120/- more than Prasad, find the share of each?

In a cricket test series, the runs made by Raju and Tendulkar are in the ratio 5:9 and Tendulkar and Azar are in the ratio 6:7. What are the runs made by them if Azar makes 187 runs more than Raju?

If A:B = 2:3 and B:C = 9:5 find A:B:C?

If A:B = 3/5:5/7 and B:C = 3/4:2/5, find A:B:C?

If R:S = 0.01:0.11 and S:T = 2.2:1, Find R:S:T?

In a school, Under a Saving Scheme, Rekha saves 3/2 times the savings of Bindu, Geeta saves 4 times the savings of Rekha. Find the ratio of the savings of all the three in least terms?

Simplification

A man left 1/3 rd of his property to his wife and 3/5 th of the remainder to his daughter. He gave the rest to his son who received Rs. 6400/-. How much was his original property worth?

Ratio and Proportion

In a school 4/9 of the pupils are boys. There are 125 girls. How many boys are there?

If A:B = 3:4 and B:C = 5:6, find A:C?

IF X:Y = 3:4 AND Y:Z = 4:5, FIND X:Y:Z?