In this lecture we continue with notable problems that are inherently solvable by dynamic programming, that is, the problem of optimal sequence alignment. Two sequences or strings are to be aligned in an optimal way given the cost of unmatching and mismatches among different symbols. This has tremendous applications in DNA sequence alignment and computational biology in general in addition to text processing such as string matching and string similarity measures, etc. The instruction language is Arabic, however, all material, slides, concepts, definitions, examples, etc., are all given in English.