Abstract—As smart phones grow in popularity, manufacturers are in a race to pack an increasingly rich set of features into these tiny devices. This brings additional complexity in the system software that has to fit within the constraints of the devices (chiefly memory, stable storage, and power consumption) and hence, new bugs are revealed. How this evolution of smartphones impacts their reliability is a question that has been largely unexplored till now. With the release of open source OSes for hand-held devices, such as, Android (open sourced in October 2008) and Symbian (open sourced in February 2010), we are now in a position to explore the above question. In this paper, we analyze the reported cases of failures of Android and Symbian based on bug reports posted by thirdparty developers and end users and documentation of bug fixes from Android developers. First, based on 628 developer reports, our study looks into the manifestation of failures in different modules of Android ...