Handheld software

Most of the software loaded on handheld computers is interactive (some exceptions are video/audio players, which are CPU-intensive). Such a software has two prominent properties. First, the execution time usually does not depend on the CPU speed, but on user interaction. Second, most system resources are dedicated to user interaction. A GUI is responsible for interacting with users. First, it presents information to users graphically, usually through GUI windows like buttons, menus, message boxes, text windows, $etc$. Second, it takes inputs from a user in the form of a user responding to GUI windows. Most GUI platforms are extended to include many non-user interface system functionalities, such as file and network operations, typically by wrapping corresponding system calls into a GUI application program interface (API). In this work, we are only concerned with those parts that present and receive user input [16].