Spin contains three functions for finding local segments of similarity between pairs of sequences ( see section Finding Similar Spans), ( see section Finding Matching Words) and ( see section Aligning Sequences Locally), and two for finding global similarity ( see section Finding the Best Diagonals) and ( see section Aligning Sequences Globally). All functions produce results which are plotted in a dot matrix display called a SPIN Sequence Comparison Plot. Obviously global similarity consists of many small matching segments and so the local similarity searches, when plotted, will also reveal any larger scale relationships.