<P> In mathematics and computer science, an algorithm (/ ˈælɡərɪðəm / (listen)) is an unambiguous specification of how to solve a class of problems . Algorithms can perform calculation, data processing and automated reasoning tasks . </P> <P> As an effective method, an algorithm can be expressed within a finite amount of space and time and in a well - defined formal language for calculating a function . Starting from an initial state and initial input (perhaps empty), the instructions describe a computation that, when executed, proceeds through a finite number of well - defined successive states, eventually producing "output" and terminating at a final ending state . The transition from one state to the next is not necessarily deterministic; some algorithms, known as randomized algorithms, incorporate random input . </P>

Working on data according to instruction is called