How instructions are understood by a computer.?

i wanna know how our instructions are actually processed by a computer. i am not searching for the phases like syntax ysis ,semantic ysis etc.. my question is.. our final machine language instructions are how actually executed??.. how logic gates will process the instructions.. i want the answer of the basic level.. for ex.. if we write printf("hello"); how it wil be executed by computer at the last level.. how it will recognise hello which will be in form of bits... also.. how actually anolog to digital conversion happens while executing.. please help me.,. these questions are buggin me from last 3 yrs... now i am in final year engg (computer science).. but still these questions are unanswered,.. please help me..