Recommendation: Unrated.
Description: Verification is a mathematical calculus for proving the correctness of algorithms and programs. It is based on a specification of the expected ('promised') results of a given method, and allows the calculation of the exact conditions under which the promised result can be guaranteed ('precondition'). The animation first motivates the verification approach and interprets the meaning of preconditions before introducing the verification of assignments. Afterwards, the animation presents how one can verify compounds (composite statements typically grouped by { ... } or BEGIN...END), conditional statements via if and while-loops. The animation also offers a simple scheme of where to put what verification part for guaranteeing correct verification.