How are computers organized? - The Tao of Computing - page 6

several files, including both the programs and the special application
data. For example, when you download and install Adobe Acrobat
Reader (to read PDF files from the World Wide Web), you download
the basic viewing software, plus quite a variety of specialpurpose
programs to handle such tasks as working with Web browsers, send
ing email, interacting with movies, reviewing spelling, and using
security options in electronic commerce. Such packages are common
when an application includes many functions, each of which comes
with one or more files.
Although the notions of programs, data, processing, and com
puter applications are reasonably precise, the term software is some
what ambiguous. Often, software refers to programs—the instruc
tions that tell a computer what to do stepbystep. In the early days
of computing, software usually had this limited meaning. However,
as programs have evolved to rely on behindthescenes application
data, the term software now may also refer to the entire computer
application.
How do computers work?
This is one of those short, simplesounding questions that
requires an extremely long answer. Consider the next few para
graphs as a first, preliminary answer; consider the entire book as a
more complete response.
Conceptually, computers may be considered as simple, elegant
machines, despite the web of wires and circuits you might see if you
open up the body of your computer. When computers perform a
task or process information, they rely on only a few fundamental
parts of their system. The connections among those components are
simple, and data flow easily among the various pieces.
In practice, this simple picture of a computer is complicated by
the need to address serious constraints, such as cost and speed. To
be useful, a computer must be affordable; expensive technology
might allow the construction of fancy or powerful computers, but
such machines would not be helpful if they cost too much. Similarly,
computers must work fast enough to meet our needs. We may not
care if computers take a few minutes to print our papers, but we
would not use them if the printing took weeks or months.