HELPROOM ANSWER WhatsApp is a very popular messaging app for smartphones, with versions available for Android, Blackberry, iOS, Symbian and Windows Phone. Notably absent are versions for desktop operating systems such as Windows and OS X.
However, you can run many Android apps, including WhatsApp, on your desktop by installing the BlueStacks App Player (reviewed here). This creates an environment in which Android apps can operate. It's still in beta, so there are issues that still need to be ironed out, but it works well enough for apps such as WhatsApp, and even some games are playable if your PC or Mac is fast enough.
It requires your phone number so it can send a text containing your security number.
The app will spend a few minutes attempting to automatically detect this SMS message before failing, at which point you can manually enter the code.
If you attempt to use WhatsApp with the same phone number on both your PC and phone, your phone will become unverified. This is because you can have a WhatsApp account only on a single device. If you want to use WhatsApp on your phone and PC, you will need to have separate accounts on each. You can do this by using a different phone number to register WhatsApp on your PC. This can be a landline number if you wish; the SMS message containing the security number will be delivered as a voice message.
WhatsApp should now work on the PC, but none of your contacts will be loaded. The simplest way to rectify this is to download a VCF file containing your contacts from mail.google.com. BlueStacks will automatically import this file.