Gopal Ji Singh : We Design Your Desire: Gopal Ji Singh

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Sunday, April 7, 2013

The First Web Server

This NeXT workstation (a NeXTcube) was used by Tim Berners-Lee as the first Web server on the World Wide Web. It is shown here as displayed in 2005 at Microcosm, the public science museum at CERN (where Berners-Lee was working in 1991 when he invented the Web).

The document resting on the keyboard is a copy of "Information Management: A Proposal," which was Berners-Lee's original proposal for the World Wide Web.

The partly peeled off label on the cube itself has the following text: "This machine is a server. DO NOT POWER IT DOWN!!"
Just below the keyboard (not shown) is a label which reads: "At the end of the 80s, Tim Berners-Lee invented the World Wide Web using this Next computer as the first Web server."
The book is probably "Enquire Within upon Everything", which TBL describes on page one of his book Weaving the Web as "a musty old book of Victorian advice I noticed as a child in my parents' house outside London".

Friday, March 15, 2013

Entrepreneurship Development Programme

Entrepreneurship Development Programme from Gopal Ji Singh

Saturday, February 9, 2013

Drag and Drop In HTML 5

Drag and Drop

Drag and drop is a very common feature. It is when you "grab" an object and drag it to a different location.

In HTML5, drag and drop is part of the standard, and any element can be draggable.

Browser Support

Internet Explorer 9, Firefox, Opera 12, Chrome, and Safari 5 support drag and drop.

Note: Drag and drop does not work in Safari 5.1.2.

HTML5 Drag and Drop Example

The example below is a simple drag and drop example:

Example

<!DOCTYPE HTML>
<html>
<head>
<script>
function allowDrop(ev)
{
ev.preventDefault();
}

function drag(ev)
{
ev.dataTransfer.setData("Text",ev.target.id);
}

function drop(ev)
{
ev.preventDefault();
var data=ev.dataTransfer.getData("Text");
ev.target.appendChild(document.getElementById(data));
}
</script>
</head>
<body>

<div id="div1" ondrop="drop(event)"
ondragover="allowDrop(event)"></div>

<img id="drag1" src="img_logo.gif" draggable="true"
ondragstart="drag(event)" width="336" height="69">

</body>
</html>

It might seem complicated, but lets go through all the different parts of a drag and drop event.

Make an Element Draggable

First of all: To make an element draggable, set the draggable attribute to true:

<img draggable="true">

What to Drag - ondragstart and setData()

Then, specify what should happen when the element is dragged.

In the example above, the ondragstart attribute calls a function, drag(event), that specifies what data to be dragged.

The dataTransfer.setData() method sets the data type and the value of the dragged data:

function drag(ev)
{
ev.dataTransfer.setData("Text",ev.target.id);
}

In this case, the data type is "Text" and the value is the id of the draggable element ("drag1").

Where to Drop - ondragover

The ondragover event specifies where the dragged data can be dropped.

By default, data/elements cannot be dropped in other elements. To allow a drop, we must prevent the default handling of the element.

This is done by calling the event.preventDefault() method for the ondragover event:

event.preventDefault()

Do the Drop - ondrop

When the dragged data is dropped, a drop event occurs.

In the example above, the ondrop attribute calls a function, drop(event):

function drop(ev)
{
ev.preventDefault();
var data=ev.dataTransfer.getData("Text");
ev.target.appendChild(document.getElementById(data));
}

Code explained:

Call preventDefault() to prevent the browser default handling of the data (default is open as link on drop)
Get the dragged data with the dataTransfer.getData("Text") method. This method will return any data that was set to the same type in the setData() method
The dragged data is the id of the dragged element ("drag1")
Append the dragged element into the drop element

Content Courtesy: http://www.w3schools.com

Monday, January 21, 2013

Classes Are Blueprints for Objects

A class describes the behavior and properties common to any particular type of object. For a string object (in Objective-C, this is an instance of the class NSString), the class offers various ways to examine and convert the internal characters that it represents. Similarly, the class used to describe a number object (NSNumber) offers functionality around an internal numeric value, such as converting that value to a different numeric type.
In the same way that multiple buildings constructed from the same blueprint are identical in structure, every instance of a class shares the same properties and behavior as all other instances of that class. Every NSString instance behaves in the same way, regardless of the internal string of characters it holds.
Any particular object is designed to be used in specific ways. You might know that a string object represents some string of characters, but you don’t need to know the exact internal mechanisms used to store those characters. You don’t know anything about the internal behavior used by the object itself to work directly with its characters, but you do need to know how you are expected to interact with the object, perhaps to ask it for specific characters or request a new object in which all the original characters are converted to uppercase.
In Objective-C, the class interface specifies exactly how a given type of object is intended to be used by other objects. In other words, it defines the public interface between instances of the class and the outside world.

Friday, April 27, 2012

Accessing Attributes With Reflection

http://iamacamera.org/images/c-sharp-reflection.jpg

The fact that you can define custom attributes and place them in your source code would be of little value without some way of retrieving that information and acting on it. C# has a reflection system that allows you to retrieve the information that was defined with custom attributes. The key method is GetCustomAttributes, which returns an array of objects that are the run-time equivalents of the source code attributes. This method has several overloaded versions. For more information, see Attribute.

An attribute specification such as:

[Author("H. Ackerman", version = 1.1)]
class SampleClass

is conceptually equivalent to this:

Author anonymousAuthorObject = new Author("H. Ackerman");
anonymousAuthorObject.version = 1.1;

However, the code is not executed until SampleClass is queried for attributes. Calling GetCustomAttributes on SampleClass causes an Author object to be constructed and initialized as above. If the class has other attributes, other attribute objects are constructed similarly. GetCustomAttributes then returns the Author object and any other attribute objects in an array. You can then iterate over this array, determine what attributes were applied based on the type of each array element, and extract information from the attribute objects.

Example

Here is a complete example. A custom attribute is defined, applied to several entities, and retrieved via reflection.

[System.AttributeUsage(System.AttributeTargets.Class |
                       System.AttributeTargets.Struct,
                       AllowMultiple = true)  // multiuse attribute
]
public class Author : System.Attribute
{
    string name;
    public double version;

    public Author(string name)
    {
        this.name = name;
        version = 1.0;  // Default value
    }

    public string GetName()
    {
        return name;
    }
}

[Author("H. Ackerman")]
private class FirstClass
{
    // ...
}

// No Author attribute
private class SecondClass
{
    // ...
}

[Author("H. Ackerman"), Author("M. Knott", version = 2.0)]
private class ThirdClass
{
    // ...
}

class TestAuthorAttribute
{
    static void Main()
    {
        PrintAuthorInfo(typeof(FirstClass));
        PrintAuthorInfo(typeof(SecondClass));
        PrintAuthorInfo(typeof(ThirdClass));
    }

    private static void PrintAuthorInfo(System.Type t)
    {
        System.Console.WriteLine("Author information for {0}", t);
        System.Attribute[] attrs = System.Attribute.GetCustomAttributes(t);  // reflection

        foreach (System.Attribute attr in attrs)
        {
            if (attr is Author)
            {
                Author a = (Author)attr;
                System.Console.WriteLine("   {0}, version {1:f}", a.GetName(), a.version);
            }
        }
    }
}

Output

Author information for FirstClass
H. Ackerman, version 1.00
Author information for SecondClass
Author information for ThirdClass
H. Ackerman, version 1.00
M. Knott, version 2.00

Definition and Uses of a Digital Certificate

http://www.pocketpcfaq.com/faqs/activesync/exchange/image001.png

A Digital Certificate allows you to establish your credentials when doing business or other transactions on the Web. You can present a Digital Certificate electronically to prove your identity or your right to access information or services online.
Digital Certificates, bind an identity to a pair of electronic keys that can be used to encrypt and sign digital information. A Digital Certificate makes it possible to verify someone's claim that they have the right to use a given key, helping to prevent people from using phony keys to impersonate other users. Used in conjunction with encryption, Digital Certificates provide a more complete security solution, assuring the identity of all parties involved in a transaction.
A Digital Certificate is issued by a Certification Authority (CA) and signed with the CA's private key. A Digital Certificate typically contains the following:

Owner's public key
Owner's name
Expiration date of the public key
Name of the issuer (the CA that issued the Digital Certificate)
Serial number of the Digital Certificate
Digital signature of the issuer

Uses of a Digital Certificate

If you are running a virtual mall, electronic banking website or any other electronic services website then customers may abandon your website due to concerns about privacy and security. A server with its own Digital Certificate assures users that the server is run by the organisation it claims to be affiliated with and that the content provided is legitimate.
Digital Certificates can be used for a variety of electronic transactions including e-mail, electronic commerce, groupware and electronic funds transfers.
For example: A customer shopping at an electronic mall requests the Digital Certificate of the server to authenticate the identity of the mall operator and the content provided by the merchant. Without authenticating the server, the shopper would not trust the operator or merchant with sensitive information like a credit card number. The Digital Certificate is instrumental in establishing a secure channel for communicating any sensitive information back to the mall operator.

Gopal Ji Singh : We Design Your Desire

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Sunday, April 7, 2013

The First Web Server

Friday, March 15, 2013

Entrepreneurship Development Programme

Saturday, February 9, 2013

Drag and Drop In HTML 5

Drag and Drop

Browser Support

HTML5 Drag and Drop Example

Example

Make an Element Draggable

What to Drag - ondragstart and setData()

Where to Drop - ondragover

Do the Drop - ondrop

Monday, January 21, 2013

Classes Are Blueprints for Objects

Friday, April 27, 2012

Accessing Attributes With Reflection

Definition and Uses of a Digital Certificate

Uses of a Digital Certificate