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Chapter 5 IT Infrastructure and Emerging Technologies 197

more apparent: The new PC makes it possible for a high-cost employee making
$100,000 a year to connect to all the company’s major systems and the public
Internet. The high-speed Internet service saves this employee about one hour
per day in reduced wait time for Internet information. Without this PC and
Internet connection, the value of this one employee to the firm might be cut
in half.

EVOLUTION OF IT INFRASTRUCTURE

The IT infrastructure in organizations today is an outgrowth of over 50 years
of evolution in computing platforms. There have been five stages in this
evolution, each representing a different configuration of computing power
and infrastructure elements (see Figure 5.2). The five eras are general-pur-
pose mainframe and minicomputer computing, personal computers, client/
server networks, enterprise computing, and cloud and mobile computing.
Technologies that characterize one era may also be used in another time
period for other purposes. For example, some companies still run traditional
mainframe systems or use mainframe computers as massive servers supporting
large Web sites and corporate enterprise applications.

General-Purpose Mainframe and Minicomputer Era:
(1959 to Present)
The introduction of the IBM 1401 and 7090 transistorized machines in 1959
marked the beginning of widespread commercial use of mainframe computers.
In 1965, the mainframe computer truly came into its own with the introduction
of the IBM 360 series. The 360 was the first commercial computer with a power-
ful operating system that could provide time sharing, multitasking, and virtual
memory in more advanced models. IBM has dominated mainframe computing
from this point on. Mainframe computers became powerful enough to support
thousands of online remote terminals connected to the centralized mainframe
using proprietary communication protocols and proprietary data lines.
The mainframe era was a period of highly centralized computing under the
control of professional programmers and systems operators (usually in a cor-
porate data center), with most elements of infrastructure provided by a single
vendor, the manufacturer of the hardware and the software.
This pattern began to change with the introduction of minicomputers pro-
duced by Digital Equipment Corporation (DEC) in 1965. DEC minicomputers
(PDP-11 and later the VAX machines) offered powerful machines at far lower
prices than IBM mainframes, making possible decentralized computing, custom-
ized to the specific needs of individual departments or business units rather than
time sharing on a single huge mainframe. In recent years, the minicomputer has
evolved into a midrange computer or midrange server and is part of a network.

Personal Computer Era: (1981 to Present)
Although the first truly personal computers (PCs) appeared in the 1970s (the
Xerox Alto, the MITS Altair 8800, and the Apple I and II, to name a few), these
machines had only limited distribution to computer enthusiasts. The appearance
of the IBM PC in 1981 is usually considered the beginning of the PC era because
this machine was the first to be widely adopted by American businesses. At first
using the DOS operating system, a text-based command language, and later the
Microsoft Windows operating system, the Wintel PC computer (Windows oper-
ating system software on a computer with an Intel microprocessor) became the
standard desktop personal computer. In 2012, there are an estimated 1.2 billion

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