Peter Shor, teaching MIT's 18.200 Principles of Discrete Applied Mathematics, works through the construction of Reed-Solomon codes using polynomials over finite fields. He shows how the fundamental theorem of algebra gives a direct way to compute the minimum distance of these codes, a key step in establishing how many errors they can tolerate. The lecture then turns to decoding, laying out the procedure for recovering the original message from a corrupted codeword. As lecture 20 in the course sequence, it assumes familiarity with earlier material on codes and finite fields, and builds toward a complete picture of why Reed-Solomon codes are both efficient and robust. The presentation is blackboard-style, with Shor working through definitions and proofs step by step rather than using slides, typical of MIT OpenCourseWare's recorded lecture format.