##Colophon This book is written in [markdown](http://daringfireball.net/projects/markdown/), which is a simplified syntax that can be compiled to HTML. It is simpler for humans to write than HTML since one does not have to type all the markup tags. The conversion from markdown to HTML is handled dynamically by a javascript library called [strapdown](https://github.com/arturadib/strapdown). It automatically does the conversion so that one can just use the markdown documents directly with no prior compilation. If you view the source of this file or any chapter document, you will see the markdown code instead of HTML. Note, for example, that ## means <h2>. Each markdown document is called by a single PHP file [is651-strapdown.php](is651-strapdown.txt) linked from the syllabus that provides the strapdown library and inserts a Home link in a CSS fixed position in the lower right-hand corner for navigation back to the syllabus/table of contents. The php link above has been saved also as .txt so you can see the PHP code. If you desire a PDF document for any chapter, you can use your printer driver from the web browser to *print to PDF*. This results in a single document with all images for easy portability. This is built into mac or linux, but [windows](http://www.howtogeek.com/150891/how-to-print-to-pdf-in-windows-4-tips-and-tricks/) needs help. The [cover illustration for the book](http://zaad2.umbc.edu/class/651/651book/is651-images/651_opt.png) was created with the program [Context Free](http://www.contextfreeart.org/). The code is: startshape forest background {a -1} rule forest { tree { } forest { z -1 s .7 y .7 x -1.5 b .1} forest { z -1 s .7 y .7 x 1.5 b .1} } rule tree { CIRCLE { s .5 1.2 } tree { s .97 y .3 r 3} } rule tree .1 { tree { flip 90 } } rule tree .1 { tree { r 10 } tree { r -10 s .6} }