I am doing a project on ISBN barcode scanning. I have tried many scanning applications but after scanning this barcode: 
the app only gives me back the barcode 9780749423490. But what I need to obtain is the ISBN code 0749423498 instead, as it is in the database of my library. Is there any method to get it?
Can anyone explain the difference between these two codes? Why is the barcode number and ISBN barcode number different? Is it the same for some books and different for some ? thanks!