lambda1@tg says to YSITD
An algorithm is just a formally specified procedure for solving a computational problem. A computation problem is just a formal description of input and output. For example, the sorting problem can be defined as follows: Input: A sequence of n numbers <a1, a2, ..., an> Output: A permutation (reordering) <a1', a2', ..., an'> of the input sequence satisfying the ordered property: a1' <= a2' <= ... <= an'