There is a WhatsApp version for PCs (Windows) which can be linked with WhatsApp on a smartphone. It requires a WhatsApp mobile version already running. However, some users have managed to register with their landline number at WhatsApp (see here).
An alternative could be to register with my mobile number, receive the SMS, and use this account. I have a very old mobile phone, but NO smartphone.
The missing part now is how to link this account with the PC version. Has someone managed to do so? Or found an alternative way?