Layman (level 1)

A series of precise instructions that can be performed by a person or a computer. For example, partial sums algorithm for adding numbers.

Algorithms can be translated into code in a programming language.

Beginner (level 2)

An unambiguous specification for performing calculation, data processing, automated reasoning, and other tasks.

Expert (level 3)

A procedure that can be implemented on a Turing machine.