Operating System & MS-DOS Guide: Features, Components and DOS Commands

What is an Operating System?

An Operating System is a set of programs that controls and coordinates the use of computer hardware among various application programs. It provides an environment within which user can execute programs.

A computer can be divided into four components:

The hardware,
The operating system,
The applications programs,
The users.

It is the operating system that manages all the above components. The various functions of the operating system are:

Controlling Input / Output devices (Keyboard, Mouse, Monitor, Printer, Plotter etc...)
Memory and File storage management
CPU Scheduling and controlling processes
Loading, initiating, executing and supervising user applications programs
Handling errors and restarting
Providing command interface between user and computer system

Examples of Operating system are: UNIX (Solaris, IRIX, HP Unix, Linux, DEC Unix) Microsoft Disk Operating System (MSDOS), WIN95/98, WIN NT, OS/2 etc.

Operating_System_&_MS-DOS_Guide_Features_Components_and_DOS_Commands

Disk operating system

Disk Operating System (specifically) and disk operating system (generically), most often reveal themselves in abbreviated as DOS, refer to an operating system software used in most computers that provides the abstraction and management of secondary storage devices and the information on them (e.g., file systems for organizing files of all sorts). Such software is referred to as a disk operating system when the storage devices it manages are made of rotating platters, such as floppy disks or hard disks.

In the early days of microcomputers, computer memory space was often limited, so the disk operating system was an extension of the operating system. This component was only loaded if needed. Otherwise, disk access would be limited to low-level operations such as reading and writing disks at the sector-level. In some cases, the disk operating system component (or even the operating system) was known as DOS.

Sometimes, a disk operating system can refer to the entire operating system if it is loaded off a disk and supports the abstraction and management of disk devices. Examples include DOS/360 and Free DOS. On the PC compatible platform, an entire family of operating systems was called DOS.

Features of MS – DOS

MS DOS is Microsoft Disk Operating System and is a precursor to Windows. The MS DOS features were slow and flunky by today's models. The system couldn't multi-task so only one program could use memory until it either finished or was stopped manually. Some features that we still see on Windows are the use of file names and lettering of the drives, to differentiate between hard drives and floppy drives for example.

Components of MS-DOS

MS-DOS consists of four essentials programs and a set of additional utilities. Four main programs are

Boot Record
IO.SYS
MSDOS.SYST
COMMAND.COM

Internal command

There are also called memory-resident commands. These commands are automatically loaded into the computer’s memory during the booting process. They actually included in the Command.com file. So, these commands are executable immediately after getting the dos prompt. A few internal commands are VER; VOL; DATE; TIME; CLS; DIR; MD; CD; PATH; RD; COPY CON; TYPE; COPY; DEL; REN and PROMT.

A command can be given in Capitals or Small letters also. The internal commands can execute immediately but External Commands require special files for their execution without which it is not possible to execute them.

VER: - All O/S has its own edition number or release or version number. The version number indicates which edition of O/S you are working on.

Syntax: VER <Enter>
Example: C:\> Ver <Enter>
Result will be: - Microsoft Windows

VOL: - It is used to display volume label and serial number of the current drive

Syntax: Vol [drive:]
Example: C:\> VOL

DATE: - Used to display the current system date and prompt for entering new date.

Syntax: Date <Enter>
Example: C:\> date <Enter>

TIME: - Displays the current system Time and prompt for entering new time.

Syntax: Time <Enter>
Example: C:\> Time <Enter>

CLS: - Clears the cluster screen.

Syntax: CLS <Enter>
Example: C:\> CLS <Enter>

DIR: - This command displays the list of directories and files with details like date of creation whether it is directory or file etc.

Syntax: DIR <Enter>
Switches:

/p: To view one screen of files at a time.
/w: Displays only five columns of filenames and directories.
/b: Display only file and directory.
/l : Display all the information in lower case letters.
/a : stands for attributes that are given below.
/-h - Hidden (or not hidden) files
s/-s - System (or not systems) files
d/-d - Directory (or not Directory) names
r/-r - Read only (or not read only) files

Example:

DIR *.txt: Display all the files with extension .txt
DIR D???. *: Display all the files starting with D and having less than or equal to
Four characters in the file name and any extension Here “?” And “*” are called “wild card character”. “*” Stand for any number of the character “?” Stands for nay one character.

MD OR MKDIR: -Used to create a new Directory or nested Directories.

Syntax: MKDIR OR MD [DRIVE:] PATH DIRECTORY NAME
Example: C:\> MD SAMS <Enter>

CD OR CHDIR: - This command allows you to change present directory to another directory.

Syntax: CD [DRIVE:] PATH
Example: C:\> CD SAMS and press <Enter>

PATH: - This command defines a list of directories DOS Searches for external commands.

Syntax: PATH (Display the current Search Path)
PATH; : - ( Clear the search path so DOS will search for external commands only in the current directory)

RD: - To delete the empty directory.

Syntax: RD [DRIVE:] PATH
NOTE: -The directory must be empty when we use RD.
Example: C:\> RD SAMS and press <Enter>
Switches: -

/s – Remove with subdirectories and files.
/q – Don’t ask to confirm.

COPY CON: -We use this command to create a new file.

Syntax: COPY CON <FILENAME>
Example: C:\> Copy Con sams.txt <Enter>
Note: - Typing here and when you are done, press Ctr+Z or F6 key followed by Enter to save the current document.

TYPE: - This command allows you to see the contents of an existing file on the screen.

SYNTAX: TYPE <file name>
Example: C:\> TYPE SAMS

COPY: - Using this command you can make duplicate files of an exiting file from one location to another or one directory to another with different name or exiting name.

SYNTAX: COPY < SOURCE FILE NAME> <TARGET FILENAME>
Example: C:\> COPY SAMS.TXT A:\TAJ
Example: C:\> COPY*.TXT +*.BAK TARGET FILENAME And Then Press Enter
Example: C:\> COPY SAMS.TXT C:\SAMS_1\FO\RECEPTION And Then Press Enter
You can also have the option to change the name of files as you copy it.
Example: C:\> COPYold.TXT C:\dos\new.txt And Then Press Enter

DEL/ERASE: This command removes one or more files from the disk or current working directories.

SYNTAX: DEL filespec [/p] or ERASE filespec [/p]
Example: C:\> DEL C:*.BAK /P And Then Press Enter
Example: C:\> DEL abc And Then Press Enter
Example: C:\> DEL ????.COM And Then Press Enter
Switches: - 1. /p –confirmation 2. /q – In quit mode

REN: Used to change the name of the file or directory.

SYNTAX: REN <file name>
Example: REN sams sams1 <Enter>
Example: REN *.dat *.mst And Then Press Enter

PROMPT: This command allows you to customize the dos prompt.

SYNTAX: 1. PROMPT
Most people like to set their prompt to $p$g which display the current directory followed by > sign.
Example: PROMPT $P$G <Enter>

TREE: - It is used to display directory structure of a specified directory graphically.

Syntax: TREE [drive:] [path] [/f]
[/F] : displays the names of the files in each directory.

External Command

These are also called Disk-Resident Commands. These commands are meant for special purpose. These are found in separate files on Hard Disk or Floppy Disk, So that they don’t typically consume valuable memory space. They are loaded into memory only when called. Some External Command is: Xcopy; Move; FC; Doskey; Mem; Attrib; Deltree; Edit and Tree

XCOPY: This command is faster than Copy Command and allows you to copy entire directories/disk including all the sub directories and files to destination.

Syntax: XCOPY Source [Target][/Y][-Y] [/P][/E]
SWITCHES:

/-Y : Prompts before copying over existing files.
/y : Overwrites existing files without prompting.
/p : Ask before copying each file.
/e : Copying empty directory also.
/s : Copying subfolders.

EXAMPLE: XCOPY C:\SAMS D:\SAMS /S/E

MOVE : This command moves a file or group of files from one directory to another and also one disk to another disk. It can also be used to rename directories.

SYNTAX: Move [Path File Name] [Destination file name path]
SWICHES:

/-Y : Prompt before it overwrites while it copies file that already exists.
/Y : Overwrites existing files without prompting.
EXAMPLE: move c:\sams\fo.txt to d:
EXAMPLE: move c:\sams\fo.txt to d:\ new_sams

FC: Stands for File Compare. If you wish to compare two files or two sets of files then you may use this command. This command has the capability to differentiate between the files and display the difference

SYNTAX: FC <files spec 1> <files spec2> [/a][/b][/c][l][/n]
Switches

/a : This switch displays only the first and last line of each group.
/b : Compare the files in library mode ( byte-by-byte)
/c : Ignore the case of letters.
/l : Compare the files in text mode.
/n : Displays the line number for lines that are different.

EXAMPLE: FC first.txt second.txt\n and then Press <enter>

DOSKEY: Dos can remember only the last command you had entered. But in order to make DOS remember all the commands you enter you will have to load a DOSKEY utility. Also Used To Create Macros

Syntax: DOSKEY and Press <Enter> Display message on the screen.
DOSKEY Installed.
NOTE: - To display all commands from the history list one the screen.
Example: DOSKEY / History or /h < Enter>.
Now when DOSKEY is in memory, it can help store all the commands which you enter so that any of those commands need not be typed again to be executed. And this all are called HISTORY LIST. Now when you want the same command to be done you can use right arrow key or ‘F1’ or ‘F3’ Issuing following command.
Second feature of DOSKEY is Doskey Macro. Using this macro you can create own command and latter you can run it on the system prompt. For example
EXAMPLE: - DOSKEY C= CLS
Now if you type at the system prompt only C and press enter it will clear the screen. Recalling Commands: Some key is provided to recall recent commands you have run since installing DOSKEY
Key Strok Effect

Up Arrow Display the Preceding Command and further list.
Down Arrow Show the next command you executed after the one that’s being displayed.
Page Up Display the oldest command that is still in Doskey.
Page Down Show the most recent command that you executed
F7 Display the entire list of command that you executedd.
F9 Selects a commands
Alt+F7 Erase the command history list.
Alt+F10 Erase all macros in memory
Esc Clear the command line.
Ctrl-T Command separator

MEM: This command displays amount of total available memory ( low, Expanded and Extended) and all currently programs.

Syntax: MEM [/f][/p][/m]
Switches:

/f : Using this switch MEM display all the areas of memory that are fee.
/p : Use this option to display the information one screen at a time.
/m : Display information about how a specified program is using memory.

Example: MEM/p and then press <Enter>

FILTER: A Powerful feature of DOS is its use of filters to process data directly. A DOS FILTER can process in unique way any data that passes through it and can change what we see on the screen.

There are three FILTERS include in DOS.
_ MORE: More command used to pause vertical Scrolling on the display screen, after each screenful, The display pauses and the message - - More - - appears. Pressing any key display the next screen.

EXAMPLE: C:\> MORE < TYPE FILE.TXT and then press <Enter>
EXAMPLE: C:\> DIR /MORE and then press <Enter>

_ SORT: Reads, Sorts in Order and sends the data to the screen, file or to another device. Sort to arrange data in an order.
SYNTAX: SORT [drive:][Path][filename][/r][+n]
Switches:
[drive:][Path][filename] : Specifies the name and location of the file to be searches. It must be preceded by the redirection character (<).
[/r] : Sort lines in reverse ASCII Order ( Z-A)
[+n] : Sorts line starting with the contents in column n. The default is 1.
EXAMPLE: C:\> SORT < NAME .TXT and then press <Enter>
EXAMPLE: C:\> SORT /+20 < PHONE .TXT and then press <Enter>
EXAMPLE: C:\> DIR / SORT > PHONE .TXT and then press <Enter>
Note: Sort command doesn’t distinguish between upper and lower case. It can sort file of maximum 63 k size. Combining Input & Output redirection :
EXAMPLE: C:\> SORT < NAME .DAT > SORTNAME.DAT and then press <Enter>
Here the sort command is being directed to take its input from <name.dat and after sorting, send its output to the > sortname.dat file.
_ FIND: The find Filter is used to search a file one or more designated character (called a text string)
Depending upon the form of the FIND Command. Each line having (or not having) the text string is sent to an output devices. Such as the Screen, a file or the printer. The text string is always typed within quotes ( “Text Sring”).
SYNTAX: FIND [/v][/c][/n] “String “ [d:] [path][filename]
Switches:

[/v] : Displays all the lines that do not contain string.
[/c] : Display the total number of lines found to contain the string.
[/n] : Display the line number as well as the line that contains the string.
[/i] : Ignores uppercase or lowercase during the search.

Where:

“String” : Specifies one or more alphabet or numeric character whose maximum length should not be more than 250 characters and must be enclosed in double quotes.
[d:] [path][filename] : Specifies the name and location of the file to be searches .
EXAMPLE: C:\> FIND “Rajni” my.txt per.txt and then press <Enter>
EXAMPLE: C:\> DIR/ FIND “TXT” and then press <Enter>

ATTRIB: Every File on the Disk has its own description like size, space occupied, the type, the date it was created, etc. Likewise, every file has few attributes. The attributes of a file indicates whether it is a i) Read-Only File: r ii) Archive File a iii) Hidden File: h iv) System File s With the ATTRIB command you can check the attributes of a file.

SYNTAX: ATTRIB [+r][+a][+h][/+s] [filename]
Switches:

+r, -r : +r Read-Only attribute or, -r turn of Read-Only attribute
+a,-a : +a archive attribute, or -a turn of archive attribute
+h,-h : +h hidden attribute, or –h turn of hidden attribute
+s, -s : +s system attribute and it should not be used generally.

Note: While creating a new file every file gets read only attribute and archive attribute by default.

EXAMPLE: C:\> ATTRIB my.txt +R and then press <Enter>
EXAMPLE: C:\> ATTRIB my.txt +H and then press <Enter>

DELTREE: This command used for deleting an entire directory whether in that directory contains files or subdirectories and also it will delete hidden files.

Syntax: DELTREE [drive:][path] directories [/y]
EXAMPLE: C:\> DELTREE my.txt and then press <Enter>

EDIT: This is the DOS Editor, which you can use to edit the text file and also creating new file.

Syntax: Edit [drive:][path][filename]
EXAMPLE: C:\> EDIT c:\sams\FO.TXT and then press <Enter>
EXAMPLE: C:\> Edit NEW FILE and then press <Enter>

BATCH FILES - It is a collection of DOS commands to perform a certain task. or A batch file is nothing but sequence of commands to perform sequence of operations step by step. Look at the following commands you give step by step to perform an operation. Suppose your job is

First - Check the directory
Second - Copy a file called ABC.txt to another disk
Third - Delete ABC.TXT from the present disk
Fourth - Clear the screen
If you do all this steps daily after your hour, then the commands you give would be:

C:\> DIR <Enter> ii) C:\> COPY C:ABC.TXT D: <Enter> iii) C:\> DEL ABC.TXT <Enter> iv) C:\> CLS <Enter>
Instead of heating yup your head daily giving the same set of commands you can do it in a much simpler manner. All you do is put all the commands in a batch file.
How to create a batch file:
C:\> COPY CON A.bat <Enter>

Note: Here Con means Console that is Keyboard, A the file name and .bat is extension. It is compulsory that a batch file must have extension .BAT. You will find the cursor below ‘A’ now type

C:\> DIR <Enter>
C:\> COPY A.TXT D : <Enter>
C:\> DEL A.TXT <Enter>
C:\> CLS <Enter>

Now Press the F6 or Ctrl+Z key combination. You shall find ^Z symbol below CLS, Now Press Enter. You will receive the following message 1files Copied.
And you are returned to the prompt C:\>
Now to execute the Batch File simply type the name of the file. C:\> A <Enter>
You will see all the commands in the A. Bat come right into action. So instead of typing all those commands one after another performed the same job by just typing the file name.

Sandeep Ghatuary

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Operating System & MS-DOS Guide: Features, Components and DOS Commands

What is an Operating System?