Explain the four criteria for proving the correctness of a logical pretest loop construct of the form "while B do S end". And prove the correctness of the following:

while B do S end

Check the explanation

Explanation:

The loop invariant has to satisfy some amount of requirements to be of good use. Another complex factor as to why a loop is the question of loop termination. A loop that doesn't terminate can't invariably be correct, and in fact the computation in whatever form amounts to nothing. The total axiomatic description of a while construct will have to involve all of the following to be true, in which I is the loop invariant:

P = > I

{I and B} S {I}

(I and (not B)) = > Q

Then the loop terminates