Offline web applications with HTML5

Web applications are preferred over desktop applications because they are available 24x7 and are accessible from anywhere in the network. A couple of years back, the term network implied wired-network but more recently, due to availability of high-speed wireless networks and handy mobile devices, the dependency over wired-network has diminished greatly. Via wireless connectivity, web applications are now accessible from literally anywhere. But there could be situations when internet connectivity may get lost. This loss of connectivity could be due to various reasons, like user is in transit or is switching between networks or is simply at a remote location where the wired/wireless network isn't available.

• Major drawback of a typical web application is that, the moment internet connectivity is lost; it can no longer be accessed or used. Most of the desktop applications do fairly well in this situation. They switch to disconnected or offline mode and ensure continuous user experience even during loss of network connectivity. Offline mode requires availability of local cache. Applications keep a copy of the online data and the data entered during the offline mode in application cache. Example of a desktop application supporting disconnected mode is e-mail client application. It caches e-mail folders and calendar appointments locally and allows browsing them in offline mode.

• Designing web application to support offline mode has been a challenge so far. Various architectural solutions exists which either requires setting trust relationship in browser or involves smart client installation. HTML5 recognized this architectural pain-point and elegantly provisioned for offline capability. Let's see how.

• Developing an offline web application has twofold issues. One, how to make web application/pages available in disconnected mode and two, how to cache large data?

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       I N F O R M A T I O N  S E C U R I T Y




There are include following:

• INTRODUCTION
• OVERVIEW OF INFORMATION SECURITY AND THE SYSTEM DEVELOPMENT LIFE CYCLE FUNDAMENTALS
• INCORPORATING SECURITY INTO THE SDLC
• ADDITIONAL SECURITY CONSIDERATIONS

Graphics in C Language

We will restrict our discussion on Graphics in C Language to 16 bit C programming and MS DOS environment.  This is done using the initgraph method provided in graphics.h library. In the next few pages we will discuss graphics.h library in details. Important functions in graphic.h library will be discuees in details and samples programmes will be provided to show the power of C programming language.

Graphics mode Initialization

First of all we have to call the initgraph function that will intialize the graphics mode on the computer. initigraph have the following prototype.

 void initgraph(int far *graphdriver, int far *graphmode, char far *pathtodriver);

*graphdriver

Integer that specifies the graphics driver to be used. You can give graphdriver a value using a constant of the graphics_drivers enumeration type.

*graphmode

Integer that specifies the initial graphics mode (unless *graphdriver = DETECT). If *graphdriver = DETECT, initgraph sets *graphmode to the highest resolution available for the detected driver. You can give *graphmode a value using a constant of the graphics_modes enumeration type.

*pathtodriver

Specifies the directory path where initgraph looks for graphics drivers (*.BGI) first.

1. If they’re not there, initgraph looks in the current directory.
2. If pathtodriver is null, the driver files must be in the current directory.

*graphdriver and *graphmode must be set to valid graphics_drivers and graphics_mode values or you’ll get unpredictable results. (The exception is graphdriver = DETECT.)

Here is a sample program that initializes the graphics mode in C Language.

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Theory of Computation

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