Chapter 2: Basics Operating System Concepts Management

(Part 1)

F2032 FUNDEMANTAL OF OPERATING SYSTEM

User InterfaceA user interface is the system by which

people (users) interact with a machine. The user interface includes hardware (physical) and software (logical) components.

User interfaces exist for various systems, and provide a means of:

- Input, allowing the users to manipulate a system, and/or

- Output, allowing the system to indicate the effects of the users' manipulation.

User Interface Users may also interact with

the operating system with some kind of software user interface like typing commands by using command line interface (CLI) or using a graphical user interface.

For hand-held and desktop computers, the user interface is generally considered part of the operating system.

On large multi-user systems such as Unix-like systems, the user interface is generally implemented as an application program that runs outside the operating system. Operating System

Placement

Components of the User Interface The user interface has two main

components:Presentation language, which is the

computer-to-human part of the transaction.Action language that characterizes the

human-to-computer portion.

Types of User Interfaces There are several types of user interfaces:

Command Line Interfaces.Menu interfaces.Graphical User Interfaces (GUIs). Voice User Interfaces.Web Form Interfaces.

Command interfacesUser types commands to give instructions

to the system e.g. UNIXMay be implemented using cheap

terminals.Easy to process using compiler techniques.Commands of arbitrary complexity can be

created by command combination.Concise interfaces requiring minimal typing

can be created.

Problems with command interfaces

Users have to learn and remember a command language. Command interfaces are unsuitable for occasional users.

Users make errors in command. An error detection and recovery system is required.

System interaction is through a keyboard so typing ability is required.

Command languagesOften preferred by experienced users

because they allow for faster interaction with the system.

Not suitable for casual or inexperienced users.

May be provided as an alternative to menu commands (keyboard shortcuts).

In some cases, a command language interface and a menu-based interface are supported at the same time.

Command-Line InterfaceCLI are often used by programmers and system

administrators, in engineering and scientific environments, and by technically advanced personal computer users.

Examples of CLI application:

Menu InterfacesMenu Interface presents user with a

menu of choices.Rather than learning specific commands,

user choose them from the menu. Menus can contain submenus, in which

case user need to memorize how to access a particular command.

This is still much easier than memorizing the actual command.

Menu Interface

Menu interfaces commonly appear the beginning of a game, often at the title screen regardless of how menus are used later in the game.

Past the opening menu, games often provide an option menu for saving. While these examples constitute menu interfaces, many games include menu interfaces to control entity actions as well.

Some games provide a series of menus through which the player controls game entities that is analogous to menu systems found in interactive kiosks.

Menu Interface

The sophistication of these menu interfaces ranges from simple, flat menus to deeply nested menus with many sub-options.

The specific representation of menu interfaces can vary as well, some games representing menus as a series of graphical buttons, others using text menus.

Menu InterfaceMenu interface provides the user with an

onscreen list of available selections.A nested menu is a menu that can be

reached through another menu.

Advantages of Menu Interface

The advantages of Menu Interface are:Less cluttered screen.Eliminate menu options which do not interest a user.Allow users to move quickly through the program.Users need not remember command names as they

are always presented with a list of valid commands.Typing effort is minimal.User errors are trapped by the interface.Context-dependent help can be provided. The user’s

context is indicated by the current menu selection.

Disadvantages of Menu InterfaceActions which involve logical conjunction

(and) or disjunction (or) are awkward to represent.

Menu systems are best suited to presenting a small number of choices. If there are many choices, some menu structuring facility must be used.

Experienced users find menus slower than command language.

Graphical User Interface (GUI)A graphical user interface or GUI (sometimes

pronounced gooey) is a type of user interface item that allows people to interact with programs in more ways than typing such as computers

Examples: hand-held devices such as MP3 Players, Portable Media Players or Gaming devices; household appliances and office equipment with images rather than text commands.

A GUI offers graphical icons, and visual indicators, as opposed to text-based interfaces, typed command labels or text navigation to fully represent the information and actions available to a user.

Graphical User Interface (GUI)The actions are usually performed through

direct manipulation of the graphical elements. Pictures tend to make the interface more

intuitive.

GUI Characteristics

Characteristic DescriptionWindows Multiple windows allow different information to be

displayed simultaneously on the user’s screen.Icons Icons different types of information. On some systems,

icons represent files; on others, icons representprocesses.

Menus Commands are selected from a menu rather than typedin a command language.

Pointing A pointing device such as a mouse is used for selectingchoices from a menu or indicating items of interest in awindow.

Graphics Graphical elements can be mixed with text on the samedisplay.

Advantages of GUIThey are easy to learn and use.

Users without experience can learn to use the system quickly.

The user may switch quickly from one task to another and can interact with several different applications.Information remains visible in its own window

when attention is switched.Fast, full-screen interaction is possible with

immediate access to anywhere on the screen.

Voice User InterfaceA Voice User Interface (VUI) makes human

interaction with computers possible through a voice/speech platform in order to initiate an automated service or process.

The VUI is the interface to any speech application.

Controlling a machine by simply talking to it was science fiction only a short time ago.

However, with advances in technology, VUI have become more common place, and people are taking advantage of the value that these hands-free, eyes-free interfaces provide in many situations.

Voice User InterfaceVoice User interface are developing rapidlyThere are two different types of voice

recognition:Continuous speech systems, allowing for

dictation.Speaker independence, so people can enter

commands or words at a given workstation.

Web Form InterfacesWeb Form interfaces are onscreen forms

displaying fields containing data items or parameters that need to be communicated to the user.

Web Form interfaces may be implemented using the Web.

Web Form InterfacesA Web Form allows a user to enter data that is

sent to a server for processing. Web forms resemble paper forms because

internet users fill out the forms using checkboxes, radio buttons, or text fields.

For example, Web Forms can be used to enter shipping or credit card data to order a product or can be used to retrieve data (e.g: searching on a search engine).

In addition to functioning as input templates for new information, Web Forms can also be used to query and display existing data in a similar manner to mail merge forms, with the same advantages.

Web Form InterfacesThe decoupling of message structure and

underlying data allow both to vary independently.

The use of Web Forms for this purpose avoids the problems associated with explicitly creating separate web pages for each record in a database.

Web Forms are defined in formal programming languages such as HTML, Perl, Php, Java or .NET.

The implementations of these languages often automatically invoke user interface idioms, such as grids and themes, minimizing programming time, costs and risks.

Advantages and Disadvantages of Web FormsAdvantages of using a Web-based form are:

User enters the data.Data may be entered 24 hours a day, globally.

Disadvantages of a Web-based form are:The experienced user may become impatient

with input/output forms.

Web Form Interface

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NEW BOOK

File SystemA file system is the part of the operating

system that is responsible for managing files and the resources on which these reside.

Without a file system, efficient computing would essentially be impossible.

File System

The file system, in collaboration with the I/O system, has the following three basic functions:

- Present a logical or abstract view of files and directories to the users by hiding the physical details of secondary storage devices and the I/O operations for communicating with the devices.

- Facilitate efficient use of the underlying storage devices.

- Support the sharing of files among different users and applications. This includes providing protection mechanisms to ensure that information is exchanged in a controlled and secure manner.

ActivityExplain how user interacts with Operating

System.List five types of User Interfaces.What are the advantages of Menu

Interface?List and explain GUI characteristics.List all the functions of File System?