All users who can use it are better off using the 64-bit version of Ubuntu. The
main difference has to do with how a computer processor is able to register
and use memory, but speed is also a factor. Here is why.
A computer with a 32-bit processor will be able to use a maximum of 4GB of
memory (actually a bit less, but this is a more practical-focused book and not
a computer science text, so the approximation is close enough for our uses;
and yes, there are exceptions, but this is a reasonable rule of thumb for those
just getting started). A computer with a 64-bit processor will be able to use up
to a theoretical limit of 17 billion GB. More memory addresses means that
you can store more data in RAM, which is much faster than processing it
while reading from and writing to disks or other storage media.
If you are dealing with large amounts of data, this is a huge benefit.
Processing audio or video, manipulating large databases of weather data, or
playing 3D video games will be much smoother. It will also happen faster.
Speed is increased for another reason. When you have more memory
addresses, it is kind of like when the supermarket has more checkout lines
open. You can process more operations simultaneously. As a result of the
extra capacity, variables and arrays in programs are processed more
efficiently, function arguments are passed more easily, and even new data
models are available for programmers and languages to use.
This requires some adaptation. Programs written for 32-bit operating systems
must generally be adapted to take advantage of the capabilities of 64-bit
processors. Although it is (usually, or at least often) possible to run 32-bit
programs on a 64-bit processor, it is not always advantageous to do so.
However, in the Linux world, including Ubuntu, most software has been
refactored and recompiled to take advantage of 64-bit processors and their
capabilities. Software written for 64-bit processors is not backward
compatible with 32-bit processors.
Early on, driver support and adaptation of software took time and was not
complete enough to recommend using 64-bit Ubuntu by default. For about a
decade, nearly all Intel- and AMD-based computer systems sold have been
64-bit, and the software has caught up. There is no reason to use anything else
on this equipment. The disc attached to this book only boots on 64-bit
machines.
If you browse to http://releases.ubuntu.com/, you will find downloadable
.iso files that will allow you to create a DVD from which you can
boot/install Ubuntu. Each is intended for a different sort of processor and
setting, such as server and desktop:
i386: This supports all Intel or compatible processors except those that