Attributes of Algorithms

The minimal set of primitives needed in order to express any algorithm:

Integer variables.
Arithmetic.
Ability to sequentially execute statements, which include assignment, selection (if), and iteration (i.e. looping: repeat).

Attributes we are interested with respect to algorithms:

First and foremost is correctness. Algorithms can be incorrect for a variety of reasons:

An algorithm/(sub)program is correct if, for all possible inputs that satisfy its

preconditions, it terminates with an output that satisfies its postconditions.