In the world of computers, a real-time operating system is designed to process data and react to it in “real time”, with allowable delays not much more ⅒ of a second.
In many ways humans (and all other animals for that matter) operate using a real time OS. The world is full of threats and opportunities and we need to respond to the former for sure but also the latter as quickly as possible to take full advantage of situations to avoid harm and secure resources.
Humans have a unique ability to create models of the future and predict what might happen. In this mental state, we are no longer real-time, but instead are doing more traditional “computing”, coming up with answers, changing the model, feeding in new info, running things again… It’s easy to get caught up in this state and ignoring the real-time input from the world coming into your senses right now, especially now that we’ve created a world where in many situations threats are very unlikely to come up (e.g. in your home or at work).
But at our core in our lower level systems, we are still a real time operating system. Even when you are lost in your thoughts about the past or future, the lower level systems are still there chugging along keeping you alive and doing their best to prevent you from harm. When I talk about “present sense”, it is turning off the thinking brain and being aware of these systems as they are working. When I do it, I notice things like how I am holding my body out of balance, orthe subtle sounds around me, or the quality of the air I am breathing… there are dozens of things that are going on around you right now if you just take the time to be with them.