Phaser is a sophisticated program for IBM personal com-puters, developed atBrown University by the author and someof his students, which enables usersto experiment withdifferential and difference equations and dynamical systemsin an interactive environment using graphics. This bookbegins with a brief discussion of the geometric inter-pretation of differential equations and numerical methods,and proceeds to guide the student through the use of theprogram. To run Phaser, you need an IBM PC, XT, AT, or PS/2with an IBM Color GRaphics Board (CGB), Enhanced GraphicsAdapter (VGA). A math coprocessor is supported; however, oneis not required for Phaser to run on the above hardware.