Basics of Computer &

Information Technology
BCOM & BCOM HON’S -3rd Year
Operating System
Module – 2
Contents

• Types of Software
• Operating Systems
• Functions of OS
• Types of OS
• History and Versions of DOS
• Windows OS
• FAT, file and directory structure
• Internal and External DOS Commands
Types of Software

• System Software
• Controls the operation
• Extends the processing capabilities of a computer system
• OS, Compilers etc.
• Application Software
• Solves a specific problem or does a specific task.
• Example – payroll processing, examination results processing, railway
reservation software, computer games, office automation software, etc.
What is an Operating System?

• Set of programs that controls

• the resources of computer
(CPU, memory, I/O devices)
• provides a virtual machine
environment to use the
hardware easily.
Functions of an OS

• Process Management
• Memory Management
• File Management
• Device Management
• Security
• Command Interpretation
• Processor Management
• In multiprogramming environment, the OS decides which process
gets the processor when and for how much time. This function is
called process scheduling. An Operating System does the following
activities for processor management −
• Keeps tracks of processor and status of process. The program
responsible for this task is known as traffic controller.
• Allocates the processor (CPU) to a process.
• De-allocates processor when a process is no longer required.
• Memory Management
• Memory management refers to management of Primary Memory or
Main Memory. Main memory is a large array of words or bytes
where each word or byte has its own address.
• Main memory provides a fast storage that can be accessed directly
by the CPU. For a program to be executed, it must in the main
memory. Keeps tracks of primary memory, i.e., what part of it are
in use by whom, what part are not in use.
• In multiprogramming, the OS decides which process will get
memory when and how much.
• Allocates the memory when a process requests it to do so.
• De-allocates the memory when a process no longer needs it or has
been terminated.
• File Management
• A file system is normally organized into directories for easy
navigation and usage. These directories may contain files and
other directions.Keeps track of information, location, uses, status
etc. The collective facilities are often known as file system.
• Decides who gets the resources.
• Allocates the resources.
• De-allocates the resources.
• Device Management –
An OS manages device communication and their respective
drivers. It performs the following activities for device
management. Keeps tracks of all devices connected to system.
designates a program responsible for every device known as the
Input/Output controller. Decides which process gets access to a
certain device and for how long. Allocates devices in an effective
and efficient way. Deallocates devices when they are no longer
required.
• Security –
The operating system uses password protection to protect user
data and similar other techniques. it also prevents unauthorized
access to programs and user data.
• Command Interpretation
• Inter-Process communication is the function of the operating
system that allows it to act as an interface for the various
processes running in the computer to use each other’s resources,
so that the process may run more efficiently. Command
interpreter is an important part of any operating system. It
provides an interface between the user and the compute
Types of OS
• Batch processing OS
• Multi-user OS
• Multi-tasking OS
• Real-time OS
• Multi-processor OS
• Embedded OS
• 1.In Batch processing os The operator collects the jobs from different users and
jobs with similar requirements were batched together and run through the
computer as a group.
• jobs in a batch are processed in the order of submission.
• Batching similar jobs helps in the utilization of system resources quite a bit. But
there were still problems. During this transaction from one job to the next, the
CPU sat idle.
• To overcome this idle time, a small program called resident monitor was created
which is always resident in the memory. It automatically sequenced from one job
to another job. The idle time for the batch system is very less and multiple users
can share the batch systems.This makes management easy for large work in batch
systems.
• 2. Multi-user software is software that allows access by
multiple users of a computer. Time-sharing systems are multi-
user systems. Most batch processing systems for mainframe
computers may also be considered "multi-user", to avoid leaving
the CPU idle while it waits for I/O operations to complete.
Multiuser is a powerful operating system that supports more than
one user at a time, performing more than one task at a time, UNIX
is an example of a multiuser operating system
• Multitasking operating system- Multitasking is a logical extension
of a multiprogramming system that supports multiple programs to
run concurrently. In a multitasking operating system, more than
one task is executed at the same time. In this technique, multiple
tasks, also known as processes, share common processing
resources such as a CPU.
• Real time OS-is an operating system intended to serve real time
application that process data as it comes in, mostly without buffer
delay. The full form of RTOS is Real time operating system.
• In a RTOS, Processing time requirement are calculated in tenths of
seconds increments of time. It is time-bound system that can be
defined as fixed time constraints. In this type of system,
processing must be done inside the specified constraints.
Otherwise, the system will fail.
• Multi Processor OS refers to the use of two or more central processing
units (CPU) within a single computer system. These multiple CPUs are in
a close communication sharing the computer bus, memory and other
peripheral devices. These systems are referred as tightly coupled
systems. These types of systems are used when very high speed is
required to process a large volume of data. system is based on the
symmetric multiprocessing model, in which each processor runs an
identical copy of operating system and these copies communicate with
each other. In this system processor is assigned a specific task. A master
processor controls the system. This scheme defines a master-slave
relationshipThe main advantage of multiprocessor system is to get more
work done in a shorter period of time.
• Embedded OS-is a specialized operating system designed to perform a
specific task for a device that is not a computer. An embedded operating
system’s main job is to run the code that allows the device to do its job.
The embedded OS also makes the device’s hardware accessible to the
software that is running on top of the OS.
• An embedded system is a computer that supports a machine. Examples
include computers in cars, traffic lights, digital televisions, ATMs
elevators, digital media receivers and smart meters, among many other
possibilities.
MS-DOS

• Disk Operating System

• Introduced by Microsoft in 1981.
• Single user, single tasking OS
• Command Line Interface (CLI) for users
• Specific set of commands for each task
Structure of MS-DOS
• MS-DOS structure consists of –
• IO.SYS file : file required to start the
computer system
• MSDOS.SYS file : file that acts as kernel
of the OS
• CONFIG.SYS file : file that manages
configuration of hardware components
• COMMAND.COM file : command
interpreter file that reads user
commands
• AUTOEXEC.BAT : batch file that consists
of list of commands executed
automatically when the computer starts
up.
MS Windows OS

• Microsoft introduced GUI (Graphical User Interface) features in a

collection of software called Windows 1.x, 2.x and 3.x.
• Developed the software into an Operating System software in
1993, called Windows NT 3.1
• After Windows NT, Windows 95, 98, 2000, 2003, Vista, XP, 2007,
Windows 8, Windows 10 , Windows 11 have been launched
• The NT Server series are multi-user and multi-tasking OS.
File Allocation Table - FAT

• File System is a method used by OS to organize files on disk.

• FAT organizes files and folders in the form of a table.
• Useful for smaller sized disks like floppy and small hard disks.
• Different types of FAT – FAT12, FAT16, FAT32
• MS-DOS file system was based on FAT16, FAT32
• NTFS (New Technology File System) replaced FAT
• NTFS manages large disks
File and Directory Structure
File Attributes

• Properties of a file
• Name
• File type
• Location
• Size
• Date and time
• Read-only
• Hidden
• archive
File naming Rules

• MS DOS allows only 8 digit file name, with 3 digit extension name.
• Allows only alphabets and numbers in filename
• Special symbols are not allowed in filename, only _ is allowed
• Filename cannot begin with a number
• Some names are restricted and cannot be used by user
• DOS
• COMMAND
• SYS
• AUTOEXEC, etc.
DOS Booting process
DOS Commands

• Internal DOS commands

• Commands that are available in the shell (command.com) part of MS DOS.
• Example – CLS, DIR, CD, MD, Copy, Del, Ren, Vol, Date, Time, Path, Type
• External DOS Commands
• Each command requires its own executable file stored in secondary memory
• Example – CHKDSK, PRINT, DISKCOPY, TREE, MOVE, LABEL, APPEND, FORMAT,
SORT, FDISK, BACKUP, ATTRIB, HELP, SYS, etc
DOS Commands – Practice
• From Windows, press Win key + R,
or open Run dialog from Start
menu
• Write the command – cmd and
press enter
• DOS command prompt is opened
• Try each DOS command here
Chkdsk

• Checks a disk and provides a file and memory status report.

• Displays error messages (if problems are found)
• CHKDSK [d:][path][filename] [/F][/V]
• /F - Corrects errors when it finds them.
• /V - Displays progress messages while CHKDSK is in operation.
Chkdsk example -

• If you enter
chkdsk a:
CHKDSK will analyze the disk in drive A and report a status message. It
will look something like this:
362496 bytes total disk space
53248 bytes in 2 hidden files
301056 bytes in 8 user files
8192 bytes available on disk
524288 bytes total memory
198976 bytes free
Print example
• To print on a selected printer (LPT1) –
• print c:\file.txt /c /d:lpt1
• To print 3 files from e: on default printer –
• print /p e:\letter.txt e:\start.exe e:\rate.com

• To stop printing and cancel the print queue, enter

print /t

print sales.doc/c oldsale.doc/p newsale.doc

diskcopy

• Makes an exact copy of a diskette. This command is used only for

copying diskettes, not hard disks.
• The first drive you specify is the drive for the source diskette. The
second is the drive for the target diskette. DISKCOPY checks to
determine if the disk in the target drive has been previously
formatted. If not, DISKCOPY will format it before it starts the copy
(except in early versions of DOS).
Diskcopy syntax

• DISKCOPY [d1:] [d2:] [/1][/V]

• Copy from drive [d1:] to drive [d2:]
• /1 - Copies only the first side of the diskette, even if the target
diskette is double sided.
/V - Verifies that the source data was copied correctly onto the
destination drive. Selecting this option will slow down the copying
process.
• Example –
• diskcopy a: b:
Tree
• Allows the user to view a listing of files and folders in an easy to read
hierarchical listing.
• Syntax –
• TREE [Drive:[[Path] [/F] [/A]
• Drive:\Path - Drive and directory containing disk for display of directory
structure.
• /F - Displays file names in each directory.
• /A - Use ASCII instead of extended characters.
• Example –
• Tree /f
Move

• Allows you to move files or directories from one folder to another, or from one
drive to another.
• To move one or more files:
MOVE [/Y | /-Y] [drive:][path]filename1[,...] destination
• To rename a directory:
MOVE [/Y | /-Y] [drive:][path]dirname1 dirname2
• /Y - Suppresses prompting to confirm you want to overwrite an existing
destination file.
• /-Y Causes prompting to confirm you want to overwrite an existing destination
file.
• Example -
• move c:\windows\temp\*.* c:\temp
Label

• used to view or change the label of the computer disk drives.

• Syntax –
• LABEL [d:][volume label]
• Input volume label - Up to 11 characters.
Press ENTER only to delete label.
• Example –
• Label e:
Append

• gives you a way to set the search path for data files.
• Is similar to the PATH command
• Path command that tells DOS where to search for program files (files
with a .COM, .EXE, or .BAT filename extension).
• The APPEND command guides the search for data files (such as text
files).
• Syntax –
• APPEND [d:]path[;][d:]path[...]
• Example –
• append c:\memos;c:\letters
Fdisk

• Fdisk is used to delete and create partitions on the hard drive in earlier
versions of MS-DOS and Windows.
• Syntax –
• FDISK [/STATUS] [/MBR]
• /Status – displays partition information of the disk
• /mbr – rewrites the master boot record.
• Example –
• Fdisk
• Fdisk /mbr
• Fdisk /status
backup

• MS-DOS application that enables users to backup their data on their

computer.
• Syntax –
• BACKUP [Source:\Path\Filename] [Target:] [/s] [/m] [/a] [/d:date]
[/t:time] [/f:size]
• Source:\Path\Filename – source file or location to backup
• Target: - target drive for the backup
• /s – backup all files and directories and subdirectories
• /m – backup all files that have changed since last backup
• /a – add new backup file to previous backup file instead of overwriting
• /d:date - Backup files that have been created or modified since
the date specified.
• /t:time - Backup files that have been created or modified after
this time.
• /f:size - Create backup files in a specific size so they can be saved
to an external storage such as a floppy disk drive.
attrib

• Attrib allows a user to change the attributes of a file or files. With attrib,
you can change any of the add or remove any of the attributes below –
• Read-only
• Archived
• Hidden
• System - makes the file an important system file.
• Syntax –
• ATTRIB [+R | -R] [+A | -A ] [+S | -S] [+H | -H] [drive:][path][filename] [/D]
• /d – process folders also
Attrib example -

• attrib +r autoexec.bat
• attrib +h config.sys
• attrib -h config.sys
• attrib +r +h *.txt
Help

• Displays help on command specified

• Syntax –
• Help [command]
• Example
• Help dir
Windows 7

• Windows 7 is an operating system that Microsoft has

produced for use on personal computers. It is the follow-
up to the Windows Vista Operating System, which was
released in 2006.
 Windows 7

• An operating system allows your computer to manage software and

perform essential tasks. It is also a Graphical User Interface (GUI) that
allows you to visually interact with your computer’s functions in a
logical, fun, and easy way
 Desktop Components

Desktop that contains many

components like icons "file, folder,
shortcut.
Task Bars
Desktop

• Folder Icons • File Icons • Shortcut Icons

Special Icons on the desktop

• Recycle bin
• My Computer
• Recycle bin:
• The Recycle Bin is a location (Folder) where deleted files are
temporarily stored on Microsoft Windows. The Recycling Bin allows
users to recover files that have been deleted in Windows.
• • My Computer:
• My Computer allows the user to explore the contents of their
computer drives as well as manage their computer files. Once My
Computer is open you'll see all available drives on your computer.
For most users, you'll only be concerned with the Local Disc (C:)
drive, which is the hard drive and what
• stores all your files.
Shortcut on the desktop
• A shortcut is a link that points to a program on the computer.
Shortcuts allow users to create links to their programs in any
folder, Start bar, Taskbar, Desktop or other locations on their
computer. A shortcut in Windows is commonly identified by a small
arrow in the bottom corner of the icon.
• The folders, often referred to as directories, are used to organize
files on your computer. The folders themselves take up virtually no
space on the hard drive.
Rename

Click the file or folder to select it

• Click the organize button on the toolbar,
and then click Rename
• With the name selected highlights, type a
new name, or click to position the insertion
point, and then edit the name.
• Press Enter
• • Right-click the file or folder you want to rename, click Rename,
type a name, and then press Enter.
• • You can also select the file, then press F2, type a name, and
then press Enter.
• • File names can be up to 255 characters. You can use spaces and
underscores in names, but you can’t use the following characters:
* : < > | ? “ \ or /. Remember the best way to keep your files
organized is with a consistent naming convention.
Copying

When you copy an item, the original item remains in its

original location— plus you have the new copy
• Open the location that contains the file you want to
copy.
• Right-click the file, and then click Copy.
• Open the location where you want to store the copy.
• Right-click an empty space within the location, and
then click Paste. The copy of the original file is now
stored in the new location.
• • Another way to copy and paste files is to use the keyboard
shortcuts Ctrl+C (Copy) and Ctrl+V (Paste).
• • You can also press and hold the right-mouse button and then
drag the file to the new location. When you release the mouse
button, click Copy here.
Moving (cut)

• Open the drive or folder containing the file or

folder you want to move.
• Select the files or folders you want to move.
• Click the Organize button on the toolbar, and then
click Cut.
• Display the destination folder where you want to
move the files or folder.
• Click the Organize button on the toolbar, and then
click Paste
• • Moving a file (or folder) is different from copying it. Moving cuts
the item from its previous location and places it in a new location.
Copying leaves the original item where it was and creates a copy
of the item elsewhere. In other words, when you copy something
you end up with two of it. When you move something, you only
have the one thing.
Copy

• Open the drive or folder containing the file or

folder you want to move.
• Select the files or folders you want to move.
• Click the Organize button on the toolbar, and then
click Cut.
• Display the destination folder where you want to
move the files or folder.
• Click the Organize button on the toolbar, and then
click Paste
• Copy or Move a File or Folder Using Drag and Drop
• • Open the drive or folder containing the file or folder you want to copy
or move.
• • Select the files or folders you want to copy or move.
• • In the Navigation pane, point to a folder list to display the expand and
collapse arrows.
• • Click the arrows to display the destination folder, and then click the
destination folder.
• • Right-click the selected files or folders, drag to the destination folder,
and then click Copy Here or Move Here.
Control Panel

• Open Control Panel by clicking the Start button

and then clicking Control Panel.
• You can use Control Panel to change settings for Windows. These
settings control nearly everything about how Windows looks and
works, and you can use them to set up Windows so that it's just
right for you.
• • Open Control Panel by clicking the Start button and then clicking
Control Panel.
• • You can display Control Panel screen with different view types
Established network connections

• 1.Click the “Network” icon in the Windows

Notification area on the right side of the taskbar. A
list of available broadcasting Wi-Fi networks opens.

2.Click the name of the network to establish a

connection. A password prompt opens if the network
is secured. Type the network password.

3.Click “Connect” to connect to the network.

• Windows 7
• Go to Start > Control Panel > Network and Internet > Network and
Sharing Center.
• In the left-hand column, click Change adapter settings.
• A new screen will open with a list of network connections. Right-
click Local Area Connection or Wireless Connection and select
Disable.