Managing Information Technology

28 Part I • Information Technology

Types of Computer Systems

We have covered the underlying structure of computers—
the six building blocks which make up all computers—and
the all-important stored-program concept. Now we want to
look at the differencesamong computers by exploring the
different types of computer systems available today. In our
discussion, we will indicate the primary uses of each type
of system as well as the major vendors. Our discussion
must begin with a significant caveat: Although there is
some agreement on the terms we will be using, there is no
such agreement on the parameters defining each category
or on the computer models that belong in each type.
Generally speaking, the boundaries between the cat-
egories are defined by a combination of cost, computing
power, and purpose for which a machine is built—but the
purposeis the dominant criterion. Listed in order of gener-
ally increasing cost and power, the categories we will use
are microcomputers, midrange systems, mainframes, and
supercomputers (see Table 2.1). You will note that the
ranges of cost and power in Table 2.1 are often overlap-
ping, which reflects the differences in purpose for which
the machines have been designed. Remember also that

MFLOPS (millions of floating point operations per sec-

ond) is only a very rough comparative measure of power.

Please note that the category boundaries in the

Table 2.1 are extremely fuzzy. The boundary between

microcomputers and midrange systems has been arbitrarily

set at $4,000, but the technology employed is quite similar

on both sides of this boundary (at least in terms of PCs and

the workstations subcategory of midrange systems). On

the other hand, the type of work done on these classes of

machines is quite different, as indicated in the table, so we

have chosen to separate them. As we discuss midrange sys-

tems, we will find that this category grew from two distinct

roots, but these subcategories now overlap so much in cost,

power, and applications that we have chosen to combine

them in a single category that stretches all the way from

microcomputers to the much larger mainframes and super-

computers. Moreover, some midrange systems use similar

technology to supercomputers—the primary difference

might be the number of parallel processors. Low-end

mainframes have significantly less power than high-end

midrange systems but have been designed for the widest

possible range of applications. Some sources use the term

TABLE 2.1 Types of Computer Systems

Category Cost MFLOPS Primary Uses

Microcomputers $200–$4,000 500–5,000 Personal computing

Client in client/serveraapplications

Web client

Small business processing

Midrange systems $4,000–$1,000,000 2,500–250,000 Departmental computing

Specific applications (office automation,

CADb, other graphics)

Midsized business general processing

Server in client/server applications

Web server, file server, local area network

server

Mainframes $500,000–$20,000,000 2,500–1,000,000 Large business general processing

Server in client/server applications

Large Web server

Widest range of applications

Supercomputers $1,000,000–$100,000,000 250,000–3,000,000,000 Numerically intensive scientific calculations

Very large Web server

aClient/server applications involve dividing the processing between a larger computer operating as a server and a smaller machine operating as a client;
this idea is explored in depth in Chapter 5.
bCAD is an abbreviation for computer-aided design, to be discussed in Chapter 5.