As the first volume in the Contemporary Mathematics and Its Applications series, this book looks at qualitative theory of difference equations with or without delays, and is written for mathematicians, engineers, biologists, and physicists or graduate students who have knowledge of calculus. Agarwal (mathematics, Florida Institute of Technology) et al. detail oscillation theory for second-order linear difference equations, systems, half-linear and non-linear, neutral, and delay difference equations, those with deviating arguments, and differential equations for piecewise constant arguments. Example equations are interspersed heavily throughout the text.