+ version 3.12.8.
+
+**For all of these groups**, a general item to take note of is what "processor architecture" your machine is running. Three of the possibilities are:
+
+* One of Intel's i386, i486, i586, i686 architectures. These are collectively known as "x86" or "IA-32" or sometimes just "32-bit".
+* Intel or AMD's x86\_64 architecture. This is sometimes also called "x64" or "amd64" or "IA-64" or sometimes just "64-bit".
+* ARM or some other architecture. These are generally lower-powered machines, like iPads. Some of the software we're proposing *might* in principle be capable of running on such machines, but installers don't seem to be available. We'll assume you have access to an x86 or x86\_64 machine.
+
+In the Linux example above, I could tell my machine is running x86 because the result of the `uname` command said "i386" at the end. Another machine I have says "x86\_64" at the end. On a Mac, you can also say `uname -m` in a Terminal session, and it will say something like "i386". I think that Mac OS's from Lion / 10.7 forward have all been x86\_64-only. On Windows, I don't know how to collect this information. But generally, machines running Windows XP will probably be i386/32-bit (unless it's a version of Windows with "64-bit" or "x64" in its title); machines running Windows Vista or Windows 7 or Windows 8 could be running either x86/32-bit or x64/64-bit.
+
+
+## PLEASE REPORT PROBLEMS (AND SOLUTIONS!) ##
+
+We haven't tested these instructions ourselves, and they're not explicit
+step-by-step instructions in any case. If you encounter troubles, please email
+to let us know so that we can amend the instructions to help others. If you
+figure out how to fix the problem youself (and please do), please also write
+with suggestions how we can change these instructions to make the process
+easier and more straightforward for others.
+
+
+## Getting Scheme ##
+
+**Scheme** is one of two major dialects of *Lisp*, which is a large family of
+programming languages. The other dialect is called "Common Lisp." Scheme is the
+more clean and minimalistic dialect, and is what's mostly used in academic
+circles.
+
+Scheme itself has umpteen different "implementations", which share most of
+their fundamentals, but have slightly different extensions and interact with
+the operating system differently. One major implementation used to be called
+PLT Scheme, but then a few years ago changed their name to Racket.
+This is what we recommend you use. (If you're already using or comfortable with
+another Scheme implementation, though, there's no compelling reason to switch.)
+
+Racket stands to Scheme in something like the relation Firefox stands to HTML. It's one program among others for working with the language; and many of those programs (or web browsers) permit different extensions, have small variations, and so on.
+
+Racket has several components. The two most visible components for us are a command-line interpreter named "racket" and a teaching-friendly editor/front-end named "DrRacket". You will probably be working primarily or wholly in the latter.
+
+<!-- racket used to be mzscheme, DrRacket used to be DrScheme -->
+
+* In your web browser:
+
+ There is a (slow, bare-bones) version of Scheme available for online use at <http://tryscheme.sourceforge.net/>.
+