Computer scientists are very interested in the efficiency of algorithms. Having an algorithm or set of directions for solving a problem is not enough. It is also important to know how much time it will take for the computer to execute all the instructions to follow the recipe from start to finish.
It is very surprising that some algorithms which are simple to state actually involve so many steps to perform that they are utterly unfeasible to use in a computer-generated solution to a problem.
To find out more about algorithms, see: