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C.S.J.M. University, Kanpur

Subject: Operating System (DCA-104)

Class: DCA 1st Semester

User Interface

A User interface (UI) facilitates communication between an application and its

user by acting as an intermediary between them. Each application including the

operating system is provided with a specific UI for effective communication. The

two basic function of a user interface of an application is to take the inputs from

the user and to provide the output to the users. A user interface of any operating

system can be classified into one of the following types:

1. Graphical user interface (GUI)

2. Character user interface (CUI)

1) Graphical user interface (GUI)

A GUI (graphical user interface) is a system of interactive visual components for

computer software. A GUI displays objects that convey information, and

represent actions that can be taken by the user. The objects change color, size, or

visibility when the user interacts with them.

Some advantages of GUI based operating system

The GUI interface is easy to understand and even the new users can

operate on them on their own.

The GUI interface visually acknowledges and confirms each type of

activities performed by the users. For example when the user deletes a file

in the Windows operating system, then the operating system asks for the

confirmation before deleting it.

The GUI interface enables the users to perform a number of tasks at the

same time. This features of the operating system are also known as

multitasking.

2) Character user interface (CUI)

Character user interface is a type of UI that enables the users to interact with the

operating system by issuing some specific commands. In order to perform a task

in this interface, the user needs to type a command at the command line. When

the user enters the key, the command line interpreter received a command. After

processing the command are called command line interpreter, the command line

interpreter displays the command prompt again along with the output of the

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previous command issued by the user. The disadvantages of the CUI is that the

user needs to remember a lot syntax to interact with the operating system.

Therefore these types of interface are not considered very friendly from the users

perspective.

Example: In order to perform a task, we need to type a command at the command

prompt denoted by C:\> to copy a text file, from the C drive of our computer

system

User based Operating System

There are two type of operating system available accordingly to user-

Single User Operating System-

A single-user operating system is a type of system that has been developed and

designed to use on a computer. It can be used on a similar device, and it only has

one user at a time. ... Single-task operating systems can function on electronic

devices, like a computer, and will run only application at a time.

Multi User Operating System-

A Multi-user operating system is a computer operating system which allows

multiple users to access the single system with one operating system on it. It is

generally used on large mainframe computers.

Example: Linux, Unix, Windows 2000, Ubuntu, Mac OS etc.,

In the multi-user operating system, different users connected at different terminals

and we can access, these users through the network as shown in the diagram.

Features of the Multi-user Operating System

• Multi-tasking- Using multi-user operating system we can perform multiple tasks

at a time, i.e. we can run more than one program at a time.

Example: we can edit a word document while browsing the internet.

• Resource sharing- we can share different peripherals like printers, hard drives or

we can share a file or data. For this, each user is given a small time slice of CPU

time.

• Background processing- It means that when commands are not processed firstly,

then they are executed in the background while another programs are interacting

with the system in the real time.

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Difference Between Single user and Multi user System

Single user Operating System Multi-user Operating System

It is an operating system in which the user can

manage one thing at a time effectively.

It is an operating system in which

multiple users can manage multiple

resources at a time

Example: MS DOS Example: Linux, Unix, windows 2000,

windows 2003 etc.

Single user Operating System has two types:

Single user Single task Operating System and

Single user Multi task Operating System.

It is of three types: time-sharing operating

system, distributed operating system and

multiprocessor system.

It is simple. It is complex.

It provides a platform for one user at a time.

It provides controlled access for the

number of users by maintaining

a database of known users.

If another user wants to access the computer

resources, then he/she has to wait until the

current process completes.

There is no need to wait for accessing the

computer resources.

This type of operating system is used for single

user.

This type of operating system is used for

multiple users.

In this, sometimes CPU is utilised to its

maximum limit.

The operating system stimulates real-time

performance by task switching.

It supports standalone systems. It doesn't support standalone systems.

It is the operating system which maximum

people use on their personal computers

or laptops.

It is the operating system which is most of

the time used in mainframe computers

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Disk Operating System (DOS)

Stands for "Disk Operating System." DOS was the first operating system used

by IBM-compatible computers. "MS-DOS" was the version that Microsoft

bought the rights to, and was bundled with the first versions of Windows.

DOS uses a command line, or character user-based interface, that allows the user

to type commands. By typing simple instructions such as md (make a directory)

and cd (change directory), the user can browse the files on the hard drive, open

files, and run programs. While the commands are simple to type, the user must

know the basic commands in order to use DOS effectively.

DOS has three important files are-

BAT (batch file)

COM (command file)

EXE (executable file)

The DOS command prompt can be opened in Windows by selecting "Run..." from

the Start Menu and typing cmd.

DOS command have three parts: File name, parameters, switches. Mostly these

commands consist of regular English word like Erase, Copy, Del etc.

There are two types of DOS Commands: Internal commands and External

commands. An internal command is embedded into the command.com file, and

an external command is not and requires a separate file to operate. Some internal

commands are-

1. Cls – This command is used to clear command prompt screen and redisplay

the command prompt at the top.

Syntax:- C : / > Cls

2. Dir – It Display the list of Directories and files on the screen.

Syntax:- C : / > dir.

a. C : / > dir/p – It displays the list of directories or files page wise

b. C: / > dir/w- It displays the list of directories or files width wise

c. C : / > dir/d: –It display list of directories or files in drive D

d. C : / > dir file . extension – It displays the information of specified file.

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3. Date – it displays current system date. User can also change existing date with

new date by using this command.

Syntax: - C : /> date

Current date is: Tue 04-07-2020

Enter of new date (mm-dd-yy):-

4. Time – It displays current system time. User can also change existing time

with new time by using this command.

Syntax : - C : / > Time

Current time is 12:39:36 p

Enter new Time : -

5. Ver – It displays the version of DOS being used currently.

6. Copy con – This command is used to create a file.

Syntax : - C : / > Copy con file name

7. Type – It displays the user to see content of a file.

Syntax :- C :/ >Type <file name>

8. Ren – The purpose of this command is to rename the old file name.

Syntax : - C : / > Ren old file name new file name

9. Del – The purpose of this command is to delete file.

Syntax : - C : / > Del file name . extension

10. MD – This command is used to create a new directory or sub directory.

Syntax : - C : /> MD directory Name

11. CD – This command is used to change one directory to another directory.

Syntax : - C : / > CD directory name

12. RD –This command is used to remove a directory or sub directory.

Syntax : - C : / > RD directory name

13. Copy – This command is used to copy one or more specified files to another

disk/drive with same file name or with different file name.

Syntax : - C : / > copy source path target path

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External command – This command is not permanent part of the memory. To

execute or run this commands an external file is required. Some commonly used

DOS external commands are-

1. Move – This command is used to move files from one location to another

location.

Syntax: C : / > Move < source path > < target path >

2. Tree – This command displays the list of directory (root directory) and files

on specified path using graphical display. It displays directories of files like

a tree.

Syntax:- C : / > tree <directory name/path> /f

3. Print – This command is allowed user to print a text file to a line printer.

Syntax : C : / > Print < files name >

4. Rmdir – This command is used to delete a root directory.

Syntax : C : / > Rmdir < directory name > /s

5. Format – Format is used to erase information of a computer fixed drive.

Syntax : - C : / > format drive name

6. Diskcopy – Diskcopy is used to make duplicate copy of the disk like Xerox

copy.

Syntax : - C : / > disk copy < source path > < destination path >

Color Command

Color attributes are specified by TWO hex digits -- the first corresponds to the

background; the second the foreground. Each digit can be any of the below

values.

0 = Black 8 = Gray

1 = Blue 9 = Light Blue

2 = Green A = Light Green

3 = Aqua B = Light Aqua

4 = Red C = Light Red

5 = Purple D = Light Purple

6 = Yellow E = Light Yellow

7 = White F = Bright White

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Syntax: color <background hexa digit & foreground hexa digit>

ATTRIB

Sets or displays the read-only, archive, system, and hidden attributes of a file or

directory.

Options

+R - Use the +R option to make a file read-only. Read-only files may be read but

they can`t be changed or deleted.

-R - Use the -R option to change the file protection attribute back to normal (so it

can be read, changed, or deleted).

+A - Use the +A option to set the ARCHIVE attribute of a file. When the +A

option is used, this flags the file as available for archiving when using the

BACKUP or XCOPY commands.

-A - Use the -A option to turn off the ARCHIVE attribute.

+H - With DOS Versions 4 through 6, use the +H option to set the HIDDEN

attribute of a file so that it will not appear in a directory listing.

-H - Use the -H option to turn off the HIDDEN attribute.

+S - With DOS Versions after Version 4, use the +S option to set the SYSTEM

attribute of a file. When the +S option is used, this flags the file as a command

file used only by DOS. The file will not appear in a directory listing. This attribute

is generally reserved for programmers.

-S - Use the -S option to turn off the SYSTEM attribute.

Batch File:

A batch file or batch job is a collection, or list, of commands that are processed in

sequence often without requiring user input or intervention. With a computer

running a Microsoft operating system such as Windows, a batch file is stored as a

file with a .bat file extension. Other operating systems may define a batch job in

a shell script, containing a list of commands to be executed one after the other.

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Batch files are often used to help load programs, run multiple processes at a time,

and perform common or repetitive tasks.

Real Time Operating System(RTOS)-

A real-time operating system (RTOS) is an operating system (OS) intended to

serve real-time applications that process data as it comes in, mostly without buffer

delays. Processing time requirements (including any OS delay) are measured in

tenths of seconds or shorter increments of time. 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.

Components of RTOS:

Features of RTOS: Here are important features of RTOS-

Occupy very less memory

Consume fewer resources

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Response times are highly predictable

Unpredictable environment

Applications of Real Time Operating System: Real-time systems are used in-

Airlines reservation system.

Air traffic control system.

Systems that provide immediate updating.

Used in any system that provides up to date and minute information on

stock prices.

Defence application systems like RADAR.

Networked Multimedia Systems

Command Control Systems

Internet Telephony

Anti-lock Brake Systems

Heart Pacemaker

Windows (GUI based operating System):

Introduction of Windows-

Microsoft Windows is a multitasking operating system developed by Microsoft

Corporation which uses Graphical User Interface to interact with the users.

Microsoft was originally named “Traf-O-Data” in 1972, was renamed as “Micro-

soft” in November 1975, then “Microsoft” on November 26, 1976. Microsoft

entered the marketplace in August 1981 by releasing version 1.0 of the operating

system Microsoft DOS (MS-DOS), a 16-bit command-line operating system. Bill

Gates and Paul Allen founded Microsoft and windows operating system has been

its primary product.

In a nutshell, below is how Microsoft windows evolved over time:

Windows 1.0 – Nov 1985

Windows 2.0 – Dec 1987

Windows 3.0 – May 1990

Windows 95 – Aug 1995

Windows 98 – June 1998

Windows ME – Sep 2000

Windows XP – Oct 2001

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Windows Vista – Nov 2006

Windows 7 – July 2009

Windows 8.0 – Oct 2012

Windows 8.1 – Oct 2013

Windows 10 – July 2015

Windows XP

Windows XP is an operating system that lets you use different types of

applications or software. For example, it allows you to use a word processing

application to write a letter and a spreadsheet application to track your financial

information.

Windows XP is a graphical user interface (GUI). It has pictures (graphical) that

you use (user) to communicate (interface) with the computer. This type of system

is popular because it's logical and easy to use.

This operating system has multi-tasking capabilities, meaning it can run several

applications at the same time. Multi-tasking allows you to view this lesson on the

Internet at the same time you practice using other applications with Windows XP.

Structure of windows XP Screen –

Windows XP uses a desktop for the standard interface. Think of the desktop as a

workspace where you can access everything you need to operate your computer,

such as system components, applications, and the Internet.

The desktop contains –

Start button- The Microsoft Windows Start menu is the primary location

in Windows to locate your installed programs and find any files or folders.

By default, the Start menu is accessed by clicking Start, which has the

Windows logo on it and is located in the bottom-left corner of the

Windows desktop screen.

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Taskbar- The taskbar is an element of an operating system located at the

bottom of the screen. It allows you to locate and launch programs

through Start and the Start menu, or view any program that is currently

open. It also allows them to check the date and time, items running in the

background through the Notification Area, and with early versions of

Windows access to the Quick Launch.

Icons- Icons is graphical representation of any applications, file and folder.

My Computer- My Computer that allows you to explore and manage the

contents of your computer drives. The image shows examples of the My

Computer icon in Microsoft Windows XP, Vista and Windows 7, as well

as the "This PC" icon in Windows 8 and in Windows 10.

Recycle Bin- It temporarily store the unused file that has been deleted in

windows. It’s like a dustbin of computer, when a file is deleted by the user;

the file can store in Recycle Bin. You can restore your deleted file from

Recycle Bin too until you deleted it permanently.

Features of Windows XP-

The main Features of Windows:

Windows Search

We can have numerous files and contents located on our system and sometimes

we may run out of memory about the exact location of our file. Windows Search

is a search function included with Windows that allows the user to search their

entire computer

Windows File Transfer

We may have the need to transfer in or transfer out the files and contents from our

machine to other devices such as other computers or mobiles and tablets. We can

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do this by using an Easy Transfer Cable, CDs or DVDs, a USB flash drive,

wireless Bluetooth, a network folder, or an external hard disk.

Windows Updates

Windows includes an automatic update feature with the intended purpose of

keeping its operating system safe and up-to-date.

Windows taskbar

At the bottom most part of your windows, you will see a row which is known as

the taskbar. It has the currently running applications, you can also pin applications

that you frequently use by using an option Pin to Taskbar”. The taskbar is the

main navigation tool for Windows

Remote Desktop Connection

This feature of windows allows you to connect to another system and work

remotely on another system.

System requirements for installing Windows 10:

These are the basic requirements for installing Windows 10 on a PC. If your

device does not meet these requirements, you may not have as great an experience

with Windows 10 and might want to consider purchasing a new PC

Processor: 1 gigahertz (GHz) or faster processor or System on a

Chip (SoC)

RAM: 1 gigabyte (GB) for 32-bit or 2 GB for 64-bit

Hard drive space: 16 GB for 32-bit OS 32 GB for 64-bit OS

Graphics card: DirectX 9 or later with WDDM 1.0 driver

Display: 800x600

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Internet

Connection:

Internet connectivity is necessary to perform updates and to

download and take advantage of some features.

Program Manager-

Program Manager refers to the basic windows of Microsoft Windows 3.x that

allow users to select and run each program on their operating system. Program

Manager contains all the .exe files of every application and program present in

the computer, and was placed in the root directory of system. Although most

prominent in Windows 3.x, Program Manager was still a part of later versions of

Windows to provide backward compatibility, and could be accessed by

typing PROGMAN.EXE on the Start Menu or Run dialog.

Control Panel:

The Control Panel is a section of Microsoft Windows that enables a user to

change various computer hardware and software features. Settings for

the mouse, display, sound, network, and keyboard represent a few examples of

what may be modified in the Control Panel.

Windows Accessory Program-

Windows comes with some additional programs that can be used in our daily life.

They can be used for text editing, painting, playing music and video files,

recording sounds etc. These programs are sufficient for elementary and midlevel

applications. You may need to by professional programs for advanced

applications, such as Microsoft word for text editing or Corel Draw for drawing.

Notepad: Notepad is basic ASCII text editor that you can use to create simple

documents. ASCII text editors display only ASCII characters and don’t store any

information like font color, text indentation or margins. The most common use

for Notepad is to view or edit text (.txt) file, but many users find Notepad a simple

tool for creating web pages.

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WordPad: WordPad is a text editing program you can use to create and edit

documents. Unlike Notepad, WordPad documents can include rich format and

graphics and you can link to or embed objects, such as pictures or other

documents. WordPad file save with .doc extension. You can also save your

WordPad file as a Rich Text Format(.RTF) or Unicode text document(.TXT).

Paint: Paint is drawing tool you can use to create simple drawings. These drawing

can be black and white or color; they can be saved as Monochrome, 24 bitmap

image(BMP), JPEG, GIF, TIFF and PNG. You can print your drawing, use it for

your desktop background.

Run Command: Using the Run Command is a quick way to open programs, files,

folders, websites etc.

Printers-

A printer produces the output from the computer on the paper. It is the most

commonly used output device. The printers produce a hard copy i.e. a permanent

copy of the results which can be stored and read later.

Printers are classified as : a) Impact Printer b) Non Impact Printer

Impact Printer: Impact printers are similar to typewriters. They use hammer to

strike a character against an inked ribbon and the impact of the hammer causes

the image of the character to be printed on paper. E.g. Dot matrix printers, line

printers, daisy wheel printers.

Advantages of impact printers:

Their functioning is relatively easy

Multiple copies can be produced at the same time with the help of carbon paper.

Impact printers are noisy in operation and are subject to wear and tear of

mechanical parts.

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Types of impact printers:

1) Dot Matrix Printers: Dot matrix printer prints each character as a pattern of

dots. The printer has a printer head with a matrix of pins (needles). Typical heads

have a matrix of 7 rows and 9 columns. These pins produce a pattern of dots to

form the individual characters.

These printers are relatively low in cost and print at speeds of 50-500

characters per second. The programmer can also define the shape of characters

for this printer. Therefore it is possible to print many special characters, characters

in various sizes as well as charts and graphs on such printers. Dot matrix printers

are very commonly used in most computer systems.

2) Daisy Wheel Printer: These printers are also called as letter quality printers.

These printers have a daisy wheel with a number of petals. A character is

embossed on each wheel. There is a motor which spins the wheel at a fast rate.

When the desired character is brought to the correct position, a hammer strikes

the petal to produce the output. Thus these printers are impact printers. The letter

quality of these printers is much superior as compared to the dot matrix printers.

But they are slow and typically print in the range of 10-50 characters per second.

3) Line Printer: Line printers are very fast printers which print at speed of 200-

2500 lines per minute. These printers are impact printers and normally have 132

print positions per line. Different types of character set are available for different

printers. Line printers are normally used in applications where large volumes of

data are to be printed.

The two types of line printers are :

(i) Drum printers This consists of a metallic cylinder. On the

surface of this drum there are characters in bands. Each column

or band on the drum contains all the characters. Opposite to each

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band there is a hammer located behind the paper. The drum

rotates at a fast rate. The hammer strikes the paper along with the

inked ribbon and produces the output. One line is printed in each

revolution of the printer.

(ii) Chain printers In the chain printers there is one print hammer

for each print position on a line. There is a fast moving chain

called the print chain. When this chain rotates, the print hammer

and the inked ribbon strike the paper against the proper character

on the chain.

b) Non-Impact Printer:

They use thermal, chemical, electrostatic and inkjet technologies for printing as

against the hammer mechanism of impact printers. e.g. Laser printers, DeskJet

printers.

Ink Jet Printer: Ink jet printer is a non-impact printer. It prints characters by

spraying ink from tiny nozzles onto the paper. A special type of ink which has a

high iron content is used. This ink is charged electrically when it comes out of the

nozzle. This ink is absorbed by the paper and dries instantly. The output of the ink

jet printer is of a superior quality. Also it is possible to obtain colored output. A

number of character styles and sizes are available. However, being a non-impact

printer it is not possible to prepare carbon copies with this printer.

Laser Printers: These printers are used where a very superior quality output is

desired. The image is created on a photo sensitive drum; with a laser beam. The

laser is turned on and off when it moves back and forward across the drum. It

leaves a negative charge on the drum to which a positively charged black toner

powder sticks. When the paper rolls by the drum, the ink is transferred to the

paper. Laser printers have a buffer memory to store entire pages and hence their

speed is very fast.

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UNIX

The Unix operating system is a set of programs that act as a link between the

computer and the user. The computer programs that allocate the system resources

and coordinate all the details of the computer's internals is called the operating

system or the kernel.

Users communicate with the kernel through a program known as the shell. The

shell is a command line interpreter; it translates commands entered by the user

and converts them into a language that is understood by the kernel.

Unix was originally developed in 1969 by a group of AT&T employees Ken

Thompson, Dennis Ritchie, Douglas McIlroy, and Joe Ossanna at Bell Labs.

There are various Unix variants available in the market. Solaris Unix, AIX, HP

Unix and BSD are a few examples. Linux is also a flavor of Unix which is freely

available.

Several people can use a Unix computer at the same time; hence Unix is called

a multiuser system.

A user can also run multiple programs at the same time; hence Unix is a

multitasking environment.

UNIX Architecture:

The main concept that unites all the versions of Unix is the following four basics

–

Kernel: The kernel is the heart of the operating system. It interacts with the

hardware and most of the tasks like memory management, task scheduling and

file management.

Shell: The shell is the utility that processes your requests. When you type in a

command at your terminal, the shell interprets the command and calls the program

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that you want. The shell uses standard syntax for all commands. C Shell, Bourne

Shell and Korn Shell are the most famous shells which are available with most of

the Unix variants.

Commands and Utilities: There are various commands and utilities which you

can make use of in your day to day activities. cp, mv, cat and grep, etc. are few

examples of commands and utilities. There are over 250 standard commands plus

numerous others provided through 3rd party software. All the commands come

along with various options.

Files and Directories: All the data of Unix is organized into files. All files are

then organized into directories. These directories are further organized into a tree-

like structure called the file system.