Introduction To MS-DOS

By Naresh Gupta



What is Operation System?

§  An operating system is a Systems Software.

§  Operating System is a control program for a Computer System that manages (or controls) the hardware resources of a computer system (Processor, Memory, Input-Output, etc) and makes a computer easy to use.

§  OS acts as an interface between the user and hardware.

§  An operating system serves three important functions – user interface, resources management, and utilities.

Example of Operating System-

Operating systems may be classified based on their characteristics.

1)  MS-DOS

2)  Windows

3)  MAC or Macintosh

4)  Unix

5)  Linux

6)  OS/2

7)  Fedora

8)  Solaris

9)  BOSS

MS-DOS – Microsoft Disk Operating System


ü  MS-DOS originally written by Tim Paterson is an American computer programmer, best known for creating 86-DOS, an operating system for the Intel-8086.

ü  This first version was shipped in August 1980.

ü  Microsoft, which needed an operating system for the IBM Personal Computer, hired Tim Paterson in May 1981 and bought 86-DOS 1.10 in July of the same year.

ü  Microsoft kept the version number, but renamed it MS-DOS.

ü  Last updated in 1994 when MS-DOS 6.22 was released.

ü  Now days, MS-DOS in no longer used.

ü  However, the command shell more commonly known at the Windows Command Line is still used by many users.

Features of MS-DOS

ü  It is a single user and Single task Operating System i.e. it can support only one user and one program at a time.

ü  CUI (Character User Interface) or CLI (Command Line Interface) based Operating System. Where all commands are entered in text form and there is no Graphical User Interface (GUI).

ü  It is 16 Bits Operating System it supports (FAT16) File Allocation Table 16 bits.

 Getting into Command Line Command Prompt


What is System File in MS-DOS?

ü  The system files are hidden files that do not show (appear) when you use the DIR command to display a directory of a system disk.

ü  MS-DOS has three essential files and many command files (set of utilities.)

ü  These essential files are:

     IO.SYS (Input Output System)

     MSDOS.SYS (Microsoft Disk Operating System)


ü  Above three files are called system files of MS-DOS.

ü  IO.SYS file take care of external resources such as keyboard, floppy drive, monitor (Manage all I/O resources) etc.

ü  MSDOS.SYS file manages internal resources of the PC such as memory, storage, processor etc. (Manage all Application Programs)

ü  COMMAND.COM works as use-system interface i.e., it contains MS-DOS commands (Internal Commands). All internal command executed/run by

What is BOOTING?

·       Booting means the process of loading the Operating System (or system files) into computer’s memory from disk is called booting.

·       So that computer starts.

·       It makes computer ready to work.

·       In booting process, the command interpreter ( and system files (io.sys, msdos.sys) are loaded into computer’s memory.

·       There are two types of Booting:

 1.   Cold Booting: Start from switching on the computer. In this stage checked POST (Power On Self-Test) operation. (Check RAM size, I/O devices etc.)

2.   Warm Booting:

o   Warm boot is done, when required after cold boot.

o   We have to perform this process when the computer hangs up.

o   We can perform it by pressing the reset button or press (Ctrl+Alt+Del) keys.

DOS Function and Editing Keys:

CTRL + S – Pause screen display

CTRL + C – Break current executing command

CTRL + ALT + DEL – to reset system

INS – Allow you to insert characters within a line

DEL – Delete one character in input buffer

ESC – Cancel line currently being displayed

F1 – Displays one character from the buffer each time

F3 – Display all character in the buffer

Reserved device names in OS

ü  CON , for console.

ü  AUX , for auxiliary.

ü  PRN , for printer.

ü  LST , for lister; introduced with 86-DOS 0.74.

ü  NUL , for null devices; added in 86-DOS 1.10 and PC DOS 1.0.

ü  COM1, COM2 for communication port

ü  LPT1, LPT2 for Parallel Port (printer)

ü  Drives Names: A: for First FDD (Floppy Disk Drive)

B: for Second FDD

C: for First HDD (Hard Disk Drive)

for Second HDD /CD/DVD drive if exist


Wild Card Characters in MS-DOS:

ü  The asterisk (*) and question mark (?) are used as wildcard characters, as they are in MS-DOS and Windows.

 ü  The asterisk matches any sequence of characters, whereas the question mark matches any single character.

Type of MS-DOS Commands:


ü  Instructions given to the computer to work are called commands.

ü  Command is common words between computer and the user.

ü  It gives the orders to the computer to work.

There are two types of MS-DOS commands

(1) Internal commands and
(2) External commands

1. Internal Commands:

Ø  Internal commands are built-in the file.

Ø  It can be executed from any MS-DOS prompt (C:\>_ or A:\>_ or D:\user>_).

Ø  Each of the Internal commands are memory resident.

Ø  As long as when computer in on, we are ready to give internal commands.

Ø  Example- CD, MD, RD, CLS, DATE, TIME, COPY, etc.

 2. External commands

Ø  External command is an MS-DOS commands that is not included in These are DOS utilities.

Ø  Come and go through the disk file.

Ø  Related program file (utility file) must be available on disk.

Ø  Run separate program files, they must be read from the disk before they executed.
Ø  External commands are known as Disk residence commands.

Ø  They are on disks as program files,   any  file name with an extension of .COM, .EXE, or .BAT is considered an  external command  (or utility).

Ø  Example: Sys, Format, Chkdsk, Scandisk, Tree, More, Mem, Mode, Print, Edit, More, Tree etc.

MS-DOS Internal commands

Environment Commands


(ये कमांड्स Computer System में internally सेट पैरामीटर को दिखाते है और new पैरामीटर/environment सेट कर सकते है l)

Directory Management Commands


(इन commands में only डायरेक्टरी का नाम ही यूज़
होगा, फ़ाइल का नाम यूज़ नहीं होगा l)

File Management Commands


(ये commands only फाइल के लिए ही वर्क करेंगे directory के लिए नहीं l)


·      DATE

·      TIME

·      PATH

·       PROMPT

·      CD or CHDIR

·      MD or MKDIR

·      RD or RMDIR


·      COPY CON

·      TYPE

·      COPY


·       DEL or ERASE

(ये commands mainly batch file में यूज़ किये
जाते है l)


(ये commands Computer की स्क्रीन (Monitor) पर कुछ इनफार्मेशन डिस्प्ले करते है l)


Things to remember:

1.    \ (Backslash or Backward slash is used to separate two directory.
E.g. C:\users\windows

2.    / (Slash or Forward slash is used to option used with command.
E.g. dir/p, dir/p/s

·      EXIT

·      ECHO on/off

·      PAUSE

·      VERIFY

·      REM

·       BREAK

·      DIR

·      CLS

·      VER

·      VOL

3.    There are two special characters * (asterisk) and ? (Question mark) are called wild-card characters in MS-DOS and Windows OS.

4.    These wild-card characters can be used with MS-DOS commands dir, copy, del, erase, ren, xcopy etc.

5.    is used to matches any sequence of characters (select files in-group. Example:


*.* refer to all files in current directory 

*.cpp refer to all files, which have file extension of .cpp.

Lbs*.* refer to all files which have first three characters Lbs.

abc*.exe refer to all files which have first three characters abc and file .extension exe


6.     ? is used to matches any single character (unknown characters). Example:


a?bd.mdb refer to file which have first char a and third and fourth chars bd and file extension .mdb.

Question: Display all file in (drive c:) on the monitor of following criteria:

1.    File name have first two chars nk and others two chars are known

2.    File extension .cpp


Answer: C:\>dir nk??*.cpp/s/p (press enter)



Directory Structure
fig :  MS-DOS Directory System

What is file?

ü  A file is a collection of related information that is stored (save) on secondary storage.

ü  The file name divided into two parts:

·       name (first name- maximum 8 characters long)

·       extension, separated by a period (3 characters long).


What is Directory?

ü  A directory is a location for storing files on your computer.

ü  Directories are found in a hierarchical file system, such as Unix, MSDOS, OS/2 and Unix.

ü  The directory contains information about the files.


What is path?

ü  PATH tells DOS, which directories should be, searched for external commands after DOS searches your working directory.

ü  DOS searches the paths in the order specified in the PATH command.

What is a file path name?

ü  To define names required to specify a particular file in a hierarchy of directories are called the path to the file, which you specify as a path name.

ü  Path names are used with commands.









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