Classical error-correcting codes under the Hamming metric are used to correct substitution and erasure errors. Motivated by the limitations of the reading process in high density data storage systems, a new class of codes called symbol-pair (metric) codes was designed to protect against pair errors in symbol-pair read channels. For a given alphabet of size $q$ and given values of $n$ and $d$ with $1\leq d\leq n$ , let $A_{p}(n,d,q)$ denote the largest possible code size for which there exists a $q$ -ary code of length $n$ with minimum pair-dist...
