Book excerpt: This book introduces mathematical computing using J a powerful new programming language with applications in mathematics, actuarial analysis, scientific research, business data processing and education. Derived from APL, J was designed as an executable mathematical notation by Dr. Kenneth E. Iverson and was implemented by Roger K.W. Hui. J unifies many areas of mathematics, has a simple consistent syntax with very few rules, yet includes a large number of functions and operators as tools for thinking and problem solving.