I would like to be able to see/monitor how a software "works" once it's running. For example I would like to see what happens internally when you click on a button, or any other interaction within an app. I tried using Instruments (xcode), but Instruments only let me select an application that's already running. Which means I always miss the initial process of when the application starts running.
I am not looking for resource usage, just trying to understand how the internal files work.