An algorithm is a finite set of rules that gives a sequence of operations for solving a specific type of problem

Algorithm: a finite set of rules that gives a sequence of operations for solving a specific type of problem.

Algorithms have 5 general characteristics:

1. Algorithms must always terminate after a finite number of steps.
2. Each step of the algorithm must be precisely defined.
3. An algorithm has zero or more inputs
4. An algorithm has one or more outputs.
5. An algorithm is generally expected to be effective. Could be done using pencil and paper

This is from The Art of Computer Programming