Despite all of the activities that we've talked about so far—communicating, coordinating, planning, designing, architecting—really, most of a software engineers time is spent reading code (Maalej et al. 2014). Sometimes this is their own code, which makes this reading easier. Most of the time, it is someone else's code, whether it's a teammate's, or part of a library or API you're using. We call this reading program comprehension.