How much amount of data can be stored in barcodes??

What type of bar code do you have in mind ?
http://en.wikipedia.org/wiki/Barcodes

You can store as much information as you want with bar codes. They're basically just another form of writing (a different "font" if you will). The amount of data you can store is simply limited to the amount of paper and ink you have.

Sorry, Ben. That's the second post in a row where I answered, only to see after the fact that you'd already answered hours earlier. I usually like to browse the entire Science category with the Go skin. I guess I'd better get in the habit of switching to the old skin before answering so I'll be able to see previous answers. :)