In C ``2*x'' means ``shift x left one bit'', an operation that most machines do very efficiently. The binary number system and why shifting left is equivalent to multiplication will be described later in this chapter, and the C programming language

is described in the chapter on programming languages.

A register is a small piece of memory large enough to hold a single number

Combining primaries to make secondary and other colors is very different for additive, light-based colors than it is for subtractive, paint-based colors. With paints, the primaries are red, blue, and yellow. As an example, combining red and yellow paint in equal proportions creates an orange paint. To create an orange light, however, one needs to combine two parts red, one part green, and no blue. X windows users who are curious to see how RGB primaries are combined to make their favorite colors can look at the system color database, usually in a file named /usr/lib/X11/rgb.txt.

What constitutes ``massive'' parallelism is not clearly defined. Most authors reserve the term for systems with 1000 or more individual processors.

A processor is said to have a ``Harvard architecture'' if it has two separate memory channels, one for instructions and one for data.

Most single-bus microprocessors use a design known as write-through cache in which values written to memory are sent simultaneously to the cache and to the main memory.

In the Linpak benchmark tables the theoretical peak performance of the Cray-1S is listed as 160 MFLOPS, probably because it was realistic to keep only two pipelines chained together for any reasonable period of time