A very basic alarm clock or timer. Uses the console. Only works on Windows x86 architecture. Not portable to linux. Uses a beep; cannot load sound / video files. You can set minutes or hours, check current time or change the beep.
On a basic level, An Alarm Clock program. cause everyone needs to get up. On a deeper level, a clock class that is assignable to objects so they can have their own sense of time. see support for required run time libraries.