>Dear All,
>
>I would like to know that what is the difference between single quotation Mark and double. please logically justify the both why we use single quote and double quote.
>

I'm not sure anyone answered the second part of your question. There are times when you need to have more than one kind of quotation mark. Sometimes you need to put a string inside a string. If it also includes an apostrophe (single quote) as part of the text, you'll need to have all three kinds of quotation marks available:

cString = ["This is the contained string that I'm writing."]

The cString variable would then contain:

"This is the contained string that I'm writing."

While that probably isn't necessary in this example, when you're constructing SQL queries and other pieces of code, you do run into this kind of situation.

Tamar