  The symbol-pair codes over finite fields have been raised for symbol-pair
read channels and motivated by application of high-density data storage
technologies [1, 2]. Their generalization is the code for b-symbol read
channels (b > 2). Many MDS codes for b-symbol read channels have been
constructed which meet the Singleton-like bound ([3, 4, 10] for b = 2 and [11]
for b > 2). In this paper we show the Plotkin-like bound and present a
construction on irreducible cyclic codes and constacyclic codes meeting the
Plotkin-like bound.
