You could already use WhatsApp on your computer and even on your iPad using WhatsApp web. However, Facebook just announced the desktop version of WhatsApp for Os X and Windows.
It is the same Whatsapp that you will see on the web version. Still, you must scan the barcode on the display. However, something that is worth mentioning is that the desktop version is native for both of the Operating systems which means you can use keyboard shortcuts.
It requires OS X 10.9 or higher on Mac, while Windows 8 or higher on PCs.