MS-DOS and Linux Commands Notes for SSC Exams
Rahul Kumar
SSC Exam Expert & Content Editor
Updated 15 Oct 2026
In this note
- 1.What Is MS-DOS?
- 2.Internal and External Commands
- 3.Important Internal DOS Commands
- 4.Important External DOS Commands
- 5.Wildcards, Redirection and Batch Files
- 6.Windows Command Prompt (CMD) Commands
- 7.What Is Linux?
- 8.Important Linux Commands
- 9.Linux File System and Permissions
- 10.DOS vs Linux Commands (Quick Comparison)
- 11.Important Questions Explained
- 12.Quick Tips to Remember
- 13.Common Mistakes to Avoid
- 14.Quick Revision Points
- 15.Practice Questions With Answers
- 16.How to Practise This Topic
- 17.Related Notes and Practice
- 18.Frequently Asked Questions
PDF Notes: MS-DOS and Linux Commands Notes for SSC Exams
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MS-DOS and Linux commands are a regular source of direct questions in SSC Computer Knowledge: which command creates a directory, which command shows the IP address, which is an internal command and which one is external. These MS-DOS and Linux commands notes for SSC give you the complete list of the important commands in tables with their meaning, plus the Windows CMD network commands, the Linux file system and 20 practice questions. Read them with the Operating System Notes, MS Windows Notes and Computer Languages and Translators Notes notes.
What Is MS-DOS?
MS-DOS (Microsoft Disk Operating System) is a command-line (CUI) operating system of Microsoft for personal computers. The user types a command at the prompt (for example C:\>) and presses Enter. MS-DOS was supplied with the IBM PC in 1981 and it was the main operating system before Windows became popular.
- It is a single-user and single-tasking operating system.
- It has no graphical interface; all work is done by typing commands.
- The boot files of MS-DOS are IO.SYS, MSDOS.SYS and COMMAND.COM. COMMAND.COM is the command interpreter (shell).
- CONFIG.SYS sets the system configuration and AUTOEXEC.BAT runs automatically at the start.
- A file name in DOS had up to 8 characters for the name and 3 characters for the extension (the 8.3 format), for example REPORT01.TXT.
- The default drive prompt is C:\>; the floppy drive was A: and B:.
- Today, the DOS-like window of Windows is the Command Prompt (cmd), opened with Windows + R and typing cmd.
Internal and External Commands
| Point | Internal commands | External commands |
|---|---|---|
| Where stored | Built into COMMAND.COM and loaded in the memory at the start | Separate files on the disk (with the extension .EXE, .COM or .BAT) |
| Speed | Faster | Slower, because they have to be loaded from the disk |
| Examples | DIR, CD, MD, RD, COPY, DEL, REN, TYPE, CLS, DATE, TIME, VER, PATH, PROMPT | FORMAT, CHKDSK, XCOPY, DISKCOPY, ATTRIB, TREE, MORE, SORT, FIND, FDISK, LABEL, EDIT |
Important Internal DOS Commands
| Command | Use |
|---|---|
| DIR | Shows the list of the files and the directories. DIR /P shows page by page; DIR /W shows in the wide format |
| CD or CHDIR | Changes the current directory; CD.. goes to the parent directory; CD\ goes to the root directory |
| MD or MKDIR | Makes (creates) a new directory |
| RD or RMDIR | Removes an empty directory |
| COPY | Copies one or more files, for example COPY A.TXT B.TXT |
| DEL or ERASE | Deletes the files |
| REN or RENAME | Changes the name of a file |
| TYPE | Shows the contents of a text file on the screen |
| CLS | Clears the screen |
| DATE | Shows or changes the system date |
| TIME | Shows or changes the system time |
| VER | Shows the version of DOS |
| VOL | Shows the volume label and the serial number of a disk |
| PATH | Shows or sets the search path for the executable files |
| PROMPT | Changes the command prompt |
| ECHO | Displays a message or switches the display of the commands on or off |
| SET | Shows or sets the environment variables |
| PAUSE | Stops the batch file until a key is pressed |
| REM | Adds a remark (comment) in a batch file |
| EXIT | Quits the command interpreter or closes the Command Prompt window |
Important External DOS Commands
| Command | Use |
|---|---|
| FORMAT | Prepares a disk for use by creating the tracks and the sectors; all the data is erased. FORMAT A: formats the floppy drive |
| CHKDSK | Checks the disk for the errors and shows the status report |
| SCANDISK | Checks and repairs the disk errors (the older DOS and Windows 9x versions) |
| XCOPY | Copies the files and the directories with the sub-directories |
| DISKCOPY | Makes an exact copy of one floppy disk on another |
| ATTRIB | Shows or changes the file attributes: read-only (R), archive (A), system (S) and hidden (H) |
| TREE | Shows the structure of the directories in a graphic form |
| MORE | Shows the output one screen at a time |
| SORT | Sorts the input and shows the result |
| FIND | Searches a text in the files |
| FDISK | Makes the partitions of the hard disk (old command) |
| LABEL | Creates or changes the volume label of a disk |
| EDIT | Opens the text editor |
| DELTREE | Deletes a directory with all its files and sub-directories |
| UNDELETE | Recovers the deleted files (old DOS versions) |
| MEM | Shows the memory usage |
Wildcards, Redirection and Batch Files
- Wildcards are special characters used in the commands: the asterisk (*) stands for any number of characters, and the question mark (?) stands for one character. For example, DIR *.TXT shows all the text files and DEL A?.DOC deletes the files like A1.DOC and AB.DOC.
- Redirection sends the output to a file with the greater-than sign (>), for example DIR > LIST.TXT; the double sign (>>) adds to the file; the less-than sign (<) takes the input from a file.
- The pipe symbol (|) sends the output of one command to another command as the input, for example DIR | MORE.
- A batch file has the extension .BAT. It is a text file that contains many commands that run one after another when its name is typed.
- Path: a full path shows the drive, the directories and the file, for example C:\SSC\NOTES\EXCEL.TXT. The first directory of a drive is the root directory.
Windows Command Prompt (CMD) Commands
| Command | Use |
|---|---|
| ipconfig | Shows the IP address, subnet mask and default gateway of the computer; ipconfig /all shows the full details including the MAC address |
| ping | Checks whether another computer or a website can be reached; it sends ICMP packets |
| tracert | Shows the route (the routers) that the packets take to reach the destination |
| netstat | Shows the network connections and the ports |
| nslookup | Finds the IP address of a domain name (DNS query) |
| hostname | Shows the name of the computer |
| tasklist | Shows the running programs (processes) |
| taskkill | Ends a running process |
| systeminfo | Shows the details of the computer and the operating system |
| shutdown | Shuts down or restarts the computer; shutdown /s /t 0 shuts it down at once |
| sfc /scannow | Scans and repairs the system files |
| chkdsk | Checks the disk for the errors |
| cls | Clears the screen |
| help | Shows the list of the commands |
What Is Linux?
- Linux is a free and open-source operating system. Its kernel was created by Linus Torvalds in 1991 as a free version of Unix.
- Unix was developed at Bell Labs (AT&T) in 1969 by Ken Thompson and Dennis Ritchie.
- Linux is multi-user and multitasking, secure and stable, so it is used in servers, supercomputers (almost all of the top supercomputers) and smartphones (Android is based on the Linux kernel).
- A distribution (distro) is a complete Linux package: Ubuntu, Debian, Fedora, Red Hat Enterprise Linux (RHEL), CentOS, Linux Mint, Kali Linux and Arch Linux. BOSS (Bharat Operating System Solutions) is an Indian Linux distribution made by C-DAC.
- The mascot of Linux is a penguin called Tux.
- The most common command-line shell of Linux is Bash (Bourne Again Shell). The commands are case-sensitive: ls is different from LS.
- The window where the commands are typed is called the terminal; the prompt ends with $ for a normal user and # for the root (administrator) user.
Important Linux Commands
| Command | Use |
|---|---|
| ls | Lists the files and directories; ls -l shows the long list with the permissions; ls -a shows the hidden files |
| cd | Changes the directory; cd .. goes up one level; cd ~ goes to the home directory |
| pwd | Shows the present working directory |
| mkdir | Creates a new directory |
| rmdir | Removes an empty directory |
| rm | Removes the files; rm -r removes a directory with its contents |
| cp | Copies the files |
| mv | Moves or renames the files |
| touch | Creates an empty file or changes the time stamp of a file |
| cat | Shows or joins the contents of a file |
| echo | Prints the text on the screen |
| man | Shows the manual (help) of a command |
| clear | Clears the terminal screen |
| chmod | Changes the permissions of a file |
| chown | Changes the owner of a file |
| grep | Searches a text pattern in the files |
| find | Searches the files in the directories |
| head / tail | Shows the first / last lines of a file |
| wc | Counts the lines, words and characters of a file |
| sort | Sorts the lines of a file |
| ps | Shows the running processes |
| top | Shows the running processes and the CPU use live |
| kill | Ends a process by its process ID (PID) |
| df | Shows the free space of the disk |
| du | Shows the disk space used by the files |
| free | Shows the free and used memory |
| uname | Shows the information about the system |
| whoami | Shows the name of the current user |
| sudo | Runs a command with the administrator (root) rights |
| passwd | Changes the password of a user |
| history | Shows the list of the commands used earlier |
| date / cal | Shows the date and time / the calendar |
| tar | Makes or opens the archive files |
| apt (or yum) | Installs and updates the software packages |
| ifconfig / ip | Shows or sets the network details |
| shutdown / reboot | Shuts down or restarts the system |
Linux File System and Permissions
| Directory | Contents |
|---|---|
| / (root) | The top of the directory tree; everything is under it |
| /bin | Basic command programs |
| /boot | The boot files and the kernel |
| /dev | Device files (hard disk, keyboard and so on) |
| /etc | Configuration files of the system |
| /home | The personal directories of the users |
| /root | The home directory of the root (administrator) user |
| /tmp | Temporary files |
| /usr | User programs and libraries |
| /var | Variable files such as logs |
| /proc | Information about the running processes |
| /mnt and /media | Places to mount the other drives |
- In Linux, everything is a file, and the directory separator is the forward slash (/), not the backslash used in DOS.
- The permissions are read (r = 4), write (w = 2) and execute (x = 1) for three groups: the owner (user), the group and others. chmod 755 gives rwx to the owner and r-x to the group and others; chmod 644 gives rw- to the owner and r-- to the others.
- The root user is the super user with all the rights.
- The hidden files of Linux start with a dot, for example .bashrc.
DOS vs Linux Commands (Quick Comparison)
| Work | MS-DOS or Windows CMD | Linux |
|---|---|---|
| List files | dir | ls |
| Change directory | cd | cd |
| Make a directory | md or mkdir | mkdir |
| Remove a directory | rd or rmdir | rmdir |
| Copy a file | copy | cp |
| Move a file | move | mv |
| Rename a file | ren | mv |
| Delete a file | del | rm |
| Show a file | type | cat |
| Clear the screen | cls | clear |
| Show the current directory | cd (without a name) | pwd |
| Show the IP details | ipconfig | ifconfig or ip addr |
| Show the running processes | tasklist | ps or top |
| End a process | taskkill | kill |
Important Questions Explained
Question 1: Which DOS command clears the screen?
Answer: CLS.
Question 2: Which command is used to create a new directory in DOS?
Answer: MD (or MKDIR).
Question 3: Is FORMAT an internal or an external DOS command?
Answer: External command.
Question 4: What does the wildcard * mean?
Answer: It stands for any number of characters, for example *.TXT means all the text files.
Question 5: Which command shows the IP address of a computer in Windows?
Answer: ipconfig.
Question 6: Which Linux command shows the present working directory?
Answer: pwd.
Question 7: Who created the Linux kernel and in which year?
Answer: Linus Torvalds, in 1991.
Quick Tips to Remember
- Remember that internal commands are built into COMMAND.COM and external commands are separate files.
- Learn the main internal commands as DIR, CD, MD, RD, COPY, DEL, REN, TYPE, CLS, DATE, TIME and VER.
- FORMAT, CHKDSK, XCOPY, DISKCOPY, ATTRIB and TREE are the favourite external commands in the exam.
- Remember * for many characters and ? for one character.
- For Linux, learn the pairs: ls (list), cd (change), pwd (present directory), cp (copy), mv (move), rm (remove) and chmod (permissions).
- Linux commands are case-sensitive, and DOS commands are not.
Common Mistakes to Avoid
- Writing FORMAT or CHKDSK as an internal command.
- Confusing RD (remove directory) with DEL (delete file).
- Mixing the wildcard * (many characters) and ? (one character).
- Writing the Linux directory separator as a backslash.
- Confusing the Linux commands rm (remove) and rmdir (remove an empty directory).
- Thinking that MS-DOS is a multitasking operating system.
Quick Revision Points
- MS-DOS: command-line, single-user, single-tasking OS of Microsoft (1981).
- Boot files: IO.SYS, MSDOS.SYS, COMMAND.COM.
- Internal: DIR, CD, MD, RD, COPY, DEL, REN, TYPE, CLS, DATE, TIME, VER.
- External: FORMAT, CHKDSK, XCOPY, DISKCOPY, ATTRIB, TREE, MORE, SORT.
- Wildcards: * and ?. Batch file: .BAT.
- CMD: ipconfig, ping, tracert, netstat, nslookup, tasklist, taskkill.
- Linux: Linus Torvalds, 1991; ls, cd, pwd, mkdir, rm, cp, mv, cat, chmod, grep.
Practice Questions With Answers
- What is the full form of MS-DOS?
Answer: Microsoft Disk Operating System (Command-line OS). - Which command lists the files in DOS?
Answer: DIR (Internal). - Which command changes the directory in DOS?
Answer: CD (Internal). - Which command removes an empty directory in DOS?
Answer: RD (Internal). - Which command is used to rename a file in DOS?
Answer: REN (Internal). - Which command is used to format a disk?
Answer: FORMAT (External). - Which command checks a disk for errors?
Answer: CHKDSK (External). - Which command copies files with sub-directories?
Answer: XCOPY (External). - What is the extension of a batch file?
Answer: .BAT (Text file of commands). - Which file is the command interpreter of MS-DOS?
Answer: COMMAND.COM (Shell). - Which symbol is the wildcard for any number of characters?
Answer: * (asterisk) (Wildcard). - Which command in Windows checks if a website is reachable?
Answer: ping (ICMP). - Which command shows the route taken by the packets in Windows?
Answer: tracert (Network). - Which Linux command shows the present directory?
Answer: pwd (Print working directory). - Which Linux command lists the files?
Answer: ls (List). - Which Linux command deletes a file?
Answer: rm (Remove). - Which Linux command changes the permissions of a file?
Answer: chmod (Change mode). - Which Linux command shows the manual of a command?
Answer: man (Manual). - Which is the home directory of the root user in Linux?
Answer: /root (Administrator). - Which symbol shows the prompt of the root user in Linux?
Answer: # (hash) ($ is for a normal user).
How to Practise This Topic
- Read the tables and learn the internal and external command lists first.
- Open the Command Prompt on your computer and try dir, cd, md, cls, ipconfig and ping.
- Revise the Linux table and the DOS and Linux comparison the next day.
- Attempt the practice questions without looking at the answers.
- Solve the SSC practice papers and the previous year papers for the pattern of operating system questions.
Related Notes and Practice
- Operating System Notes
- Computer Languages and Translators Notes
- Computer Shortcut Keys
- Internet and Networking Notes
- Computer Knowledge Notes for SSC
- SSC practice papers
Frequently Asked Questions
What is MS-DOS?
MS-DOS (Microsoft Disk Operating System) is a command-line operating system of Microsoft in which the user types the commands to work on the computer.
What is the difference between internal and external DOS commands?
Internal commands are built into COMMAND.COM and load in the memory at the start, while external commands are separate files stored on the disk.
Which are the internal commands of DOS?
Some important internal commands are DIR, CD, MD, RD, COPY, DEL, REN, TYPE, CLS, DATE, TIME and VER.
Which are the external commands of DOS?
Some important external commands are FORMAT, CHKDSK, XCOPY, DISKCOPY, ATTRIB, TREE, MORE and SORT.
What are wildcards in DOS?
Wildcards are special characters used to stand for other characters. The asterisk (*) stands for many characters and the question mark (?) stands for one character.
What is a batch file?
A batch file is a text file with the extension .BAT that contains many commands that run one after another.
What does the ipconfig command do?
The ipconfig command shows the IP address, the subnet mask and the default gateway of the computer.
What is Linux?
Linux is a free and open-source, multi-user operating system whose kernel was created by Linus Torvalds in 1991.
What is a Linux distribution?
A distribution (distro) is a complete Linux operating system package such as Ubuntu, Debian, Fedora or Red Hat.
What does the chmod command do?
The chmod command changes the read, write and execute permissions of a file or a directory.
Are Linux commands case-sensitive?
Yes. In Linux, ls and LS are different, while DOS commands are not case-sensitive.
How many questions come from commands in SSC exams?
Usually one question comes from DOS or Linux commands in the Computer Knowledge section.
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About the Author
Rahul Kumar
SSC Exam Expert & Content Editor
Rahul is a senior SSC exam strategist with 8+ years of experience helping aspirants crack CGL, CHSL and MTS exams. He writes in-depth notification breakdowns, exam pattern guides and preparation strategies.