# PrefacePreface

This version of *Applied Discrete Structures* is being developed using *Mathbook XML*, a lightweight XML application for authors of scientific articles, textbooks and monographs initiated by Rob Beezer, U. of Puget Sound.

We embarked on this open-source project in 2010. The choice of Mathematica for “source code” was based on the speed with which we could do the conversion. However, the format was not ideal, with no viable web version available. The project has been well-received in spite of these issues. Validation through the listing of this project on the American Institute of Mathematics has been very helpful. When the MBX project was launched, it was the natural next step. The features of MBX make it far more readable than our first versions, with web, pdf and print copies being far more readable.

Twenty-one years after the publication of the 2nd edition of Applied Discrete Structures for Computer Science, in 1989 the publishing and computing landscape had both changed dramatically. We signed a contract for the second edition with Science Research Associates in 1988 but by the time the book was ready to print, SRA had been sold to MacMillan. Soon after, the rights had been passed on to Pearson Education, Inc. In 2010, the long-term future of printed textbooks is uncertain. In the meantime, textbook prices (both printed and e-books) have increased and a growing open source textbook market movement has started. One of our objectives in revisiting this text is to make it available to our students in an affordable format. In its original form, the text was peer-reviewed and was adopted for use at several universities throughout the country. For this reason, we see Applied Discrete Structures as not only an inexpensive alternative, but a high quality alternative.

As indicated above the computing landscape is very different from the 1980's and accounts for the most significant changes in the text. One of the most common programming languages of the 1980's was Pascal. We used it to illustrate many of the concepts in the text. Although it isn't totally dead, Pascal is far from the mainstream of computing in the 21st century. In 1989, Mathematica had been out for less than a year — now a major force in scientific computing. The open source software movement also started in the late 1980's and in 2005, the first version of Sage, an open-source alternative to Mathematica, was first released. In Applied Discrete Structures we have replaced "Pascal Notes" with "Mathematica Notes" and "Sage Notes." Finally, 1989 was the year that specifications for World Wide Web was laid out by Tim Berners-Lee. There wasn't a single www in the 2nd edition.

Sage (sagemath.org) is a free, open source, software system for advanced mathematics. Sage can be used either on your own computer, a local server, or on SageMathCloud (https://cloud.sagemath.com).

Ken LevasseurLowell MA