Chapter 2 • Computer Systems 41more depth in Chapter 14. ACT! by Sage (United
Kingdom), GoldMine (from FrontRange Solutions), and
Now Software’s Up-to-date & Contact are examples of
contact managementproducts to let the user track past and
potential customers.
Project scheduling software includes Microsoft
Office Project, Project KickStart Pro, and Tenrox Online
Project Management. Among the popular products for
image editingare Adobe Photoshop Elements, Corel
Paint Shop Pro Photo (Canada), and Serif PhotoPlus. For
video editing, three strong software products are Adobe
Premiere Elements, Corel Video Studio, and CyberLink
PowerDirector (Taiwan). Valuable utility productsinclude
Roxio Creator (to burn CDs and DVDs) and Roxio
BackOnTrack Suite (a PC backup solution).
The list of personal productivity software presented
here could certainly be extended with additional categories
and additional products, but the list provided should illus-
trate the richness of the offerings available.
Support Software
Support software has been designed to support applica-
tions software from behind the scenes rather than to
directly produce output of value to the user. There are
several types of support software, as shown in Figure 2.8.
We now want to take a systematic look at the various types
of support software, beginning with the all-important
operating system.
The Operating System
The most important type of support software is the operat-
ing system, which originated in the mid-1960s and is now
an integral part of every computer system. The operating
systemis a very complex program that controls the opera-
tion of the computer hardware and coordinates all the other
software, so as to get as much work done as possible with
the available resources. Users interact with the operating
system, and the operating system in turn controls all hard-
ware and software resources of the computer system.
How does the computer user tell the operating sys-
tem what he or she wants to have done? For a PC or a Mac,
the user finds and then clicks on an appropriate icon or
label to start a program or retrieve a data file. For a larger
machine, the user must provide instructions expressed in
the particular job control language (JCL)that is under-
stood by the operating system being used. This job control
language varies significantly from one operating system to
the next, both in terms of the types of instructions and the
detailed syntax. To run a payroll program, for example,
JCL is used to tell the operating system the name of the
program to be run, the names of the data files that are needed,
instructions for output of data, and the account number
to be charged, among other things.
There are two overriding purposes for an operating
system: to maximize the work done by the computer sys-
tem (the throughput) and to ease the workload of computer
users. In effect, the operation of the computer system has
been automated through the use of this sophisticated
program. The operating system is critical for all types of
computers, although it is perhaps more critical for large
computers where many programs may be running at the
same time and many peripheral devices are involved. On
large computers, for instance, the operating system—using
priority rules specified by the computer center manager—
decides when to initiate a particular job from among those
waiting in the input queue. The operating system decides
which job to print next, again based on priority rules. On
large machines, the operating system also controls the
inflow and outflow of communications with the various
terminals and microcomputers in its network. On both
large and small computers, the operating system stores and
retrieves data files, keeping track of where everything is
stored (a function sometimes shared with a database man-
agement system). Similarly, the operating system manages
the software library, keeping track of both support and
applications programs.
The advantage of letting the operating system per-
form all the previously mentioned tasks is that it can react
at electronic speed to select a job to run, select the appro-
priate software from the library, and retrieve the appropri-
ate data file. Thus, the powerful central processing unit
(CPU) can be kept as busy as possible, and the throughput
from the system can be maximized. Further, the operating
system can create a computing environment—in terms of
what computer users or operators see on their screens and
what they need to do to tell the operating system what they
want done—in which it is relatively easy to work.ADVANCED OPERATING SYSTEMS CONCEPTS^7
Operating systems often incorporate two important con-
cepts—multiprogramming and virtual memory—in order
to increase the efficiency of the computer’s operations. On
large computers, multiprogrammingis often employed
to switch among programs stored in memory in order to
overlap input and output operations with processing time.
In effect, this allows the computer to carry out several pro-
grams at the same time. On microcomputers, the term(^7) For a more complete description of the advanced operating systems con-
cepts introduced in this section, see the Companion Web site for this book
at http://www.pearsonhighered.com/brown and look for the “Advanced
Operating Systems Concepts” link.