The prerequisites for this book are that you have an installation of gnuplot available for your use and that you are familiar with elementary gnuplot operation (starting gnuplot on the command line and entering a plot command). You should be able to create plots on one of the screen terminals and to save a plot file, as well. Other than that, no specialized knowledge is required to make use of this guide; although we may take examples from various specialized fields, they are incidental to the recipes, which are focused on creating particular types of graphs. The examples of controlling gnuplot from programming languages use simple examples that can be understood even if you don't have experience with the languages used in the recipes.