  In program algebra, an algebraic theory of single-pass instruction sequences,
three congruences on instruction sequences are paid attention to: instruction
sequence congruence, structural congruence, and behavioural congruence. Sound
and complete axiom systems for the first two congruences were already given in
early papers on program algebra. The current paper is the first one that is
concerned with an axiom system for the third congruence. The presented axiom
system is especially notable for its axioms that have to do with forward jump
instructions.
