The three subjects of this book all began life in the provinces of applicable mathematics. Design theory originated in statistics (its name reflects its initial use, in experimental design); codes in information transmission; and graphs in the modeling of networks of a very general kind (in the first instance, the bridges of Konigsberg). All three have since become part of mainstream discrete mathematics.

1. Design theory; 2. Strongly regular graphs; 3. Graphs with least eigenvalue -2; 4. Regular two-graphs; 5. Quasi-symmetric designs; 6. A property of the number 6; 7. Partial geometries; 8. Graphs with no triangles; 9. Codes; 10. Cyclic codes; 11. The Golay codes; 12. Reed-Muller codes; 13. Self-dual codes and projective plane; 14. Quadratic residue codes and the Assmus-Mattson theorem; 15. Symmetry codes over F3; 16. Nearly perfect binary codes and uniformly packed codes; 17. Association schemes.