WhatsApp has seen quite a bit of functionality added to the application since Facebook bought them in 2014. And it looks like the team working on WhatsApp is pushing out a few new changes to the application. One of those changes is a new font, which they call 'Fixedsys'. Now this isn't enabled by default, so all of your messages won't be using this font. And it's here to make code look a bit different. To enable Fixedsys font, simply type "` before and after your message. This builds on the other formatting changes that WhatsApp added a few months ago.
When it comes to making calls in WhatsApp, that functionality hasn't actually changed. What has changed, however, is the options after declined or unanswered calls are made. Instead of being thrown back into the chat screen, you will now see a variety of options. One is to call the person back, another is to go back to your conversation with that person, and the third is to record a voice message to send to them. This makes it easier for users to leave a voicemail for the contact that they were trying to reach – even though it's technically called a "voice note" in WhatsApp.
There's also a new message that will appear in chats, it says "Waiting for this message. This may take a while". Essentially what is happening here is that WhatsApp knows it should be delivering a message to you, but it hasn't downloaded it completely yet. It's likely that you won't see this message often or even at all, since most messages in WhatsApp are just text, so they don't need much bandwidth to download and be sent to your device. But it is still a nice addition, especially those that might be using WhatsApp on a slower connection like EDGE or even GPRS.
These changes are all part of the latest beta, if you're interested in checking out the beta, you can do so at the link down below. Just keep in mind that this is indeed a beta version of WhatsApp and there are likely plenty of bugs inside.