Algorithm/definition•Not all processes are algorithms, however.•To be an algorithm, a process must have the following properties:1.It must be unambiguous. In other words, it must be possible to describe every step of the process in enough detail that anyone (even a machine) can carry out the algorithm in the way intended by its designer. This requires not only knowing exactly how to perform each step, but also the exact order in which the steps should be performed. 
Algorithm/definition2.It must always solve the problem. In other words, a person (or machine) who starts carrying out the algorithm in order to solve an instance of the problem must be able to stop with the correct answer after performing a finite number of steps. You must eventually reach a correct answer no matter what instance of the problem you started with.
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Algorithm/definition•These two properties defined in the previous slide lead to the following concise definition: •an algorithm is a finite, ordered sequence of unambiguous steps that leads to a solution to a problem.
Algorithm•The study of algorithms also involves the study of the data that algorithms process, because the nature of an algorithm often follows closely from the nature of the data on which the algorithm works.