Information Technology Reference
In-Depth Information
SUMMARY
Principle
Systems and application software are critical in help-
ing individuals and organizations achieve their goals.
connect mainframes and personal computers to share
resources. Linux is the kernel of an OS whose source code is
freely available to everyone. Several variations of Linux are
available, with sets of capabilities and applications to form a
complete OS, for example, Red Hat Linux. z/OS and HP-UX
are OSs for mainframe computers. Some OSs, such as Palm
OS, Windows Mobile, Windows Embedded, Pocket PC, and
variations of Linux, have been developed to support mobile
communications and consumer appliances.
Utility programs can perform many useful tasks and often
come installed on computers along with the OS. This software
is used to merge and sort sets of data, keep track of computer
jobs being run, compress files of data, protect against harmful
computer viruses, and monitor hardware and network per-
formance. Middleware is software that allows different sys-
tems to communicate and transfer data back and forth. A
service-oriented architecture (SOA) uses modular application
services to allow users to interact with systems, and systems
to interact with each other.
Software consists of programs that control the workings of
the computer hardware. The two main categories of software
are systems software and application software. Systems
software is a collection of programs that interacts between
hardware and application software, and includes operating
systems, utility programs, and middleware. Application
software can be proprietary or off the shelf, and enables
people to solve problems and perform specific tasks.
An operating system (OS) is a set of computer programs
that controls the computer hardware to support users'
computing needs. An OS converts an instruction from an
application into a set of instructions needed by the hardware.
This intermediary role allows hardware independence. An OS
also manages memory, which involves controlling storage
access and use by converting logical requests into physical
locations and by placing data in the best storage space,
including virtual memory.
An OS manages tasks to allocate computer resources
through multitasking and time-sharing. With multitasking,
users can run more than one application at a time. Time-
sharing allows more than one person to use a computer
system at the same time.
The ability of a computer to handle an increasing number
of concurrent users smoothly is called scalability, a feature
critical for systems expected to handle a large number of
users.
An OS also provides a user interface, which allows users
to access and command the computer. A command-based
user interface requires text commands to send instructions;
a graphical user interface (GUI), such as Windows, uses icons
and menus.
Software applications use the OS by requesting services
through a defined application program interface (API).
Programmers can use APIs to create application software
without having to understand the inner workings of the OS.
APIs also provide a degree of hardware independence so that
the underlying hardware can change without necessarily
requiring a rewrite of the software applications.
Over the years, several popular OSs have been developed.
These include several proprietary OSs used primarily on
mainframes. MS-DOS is an early OS for IBM-compatibles.
Older Windows OSs are GUIs used with DOS. Newer versions,
such as Windows Vista and XP, are fully functional OSs that
do not need DOS. Apple computers use proprietary OSs such
as the Mac OS and Mac OS X. UNIX is a powerful OS that can
be used on many computer system types and platforms, from
personal computers to mainframe systems. UNIX makes it
easy to move programs and data among computers or to
Principle
Organizations should not develop proprietary appli-
cation software unless doing so will meet a com-
pelling business need that can provide a competitive
advantage.
Application software applies the power of the computer to
solve problems and perform specific tasks. One useful way of
classifying the many potential uses of information systems is
to identify the scope of problems and opportunities addressed
by a particular organization or its sphere of influence. For
most companies, the spheres of influence are personal,
workgroup, and enterprise.
User software, or personal productivity software, includes
general-purpose programs that enable users to improve their
personal effectiveness, increasing the quality and amount of
work that can be done. Software that helps groups work
together is often called workgroup application software, and
includes group scheduling software, electronic mail, and
other software that enables people to share ideas. Enterprise
software that benefits the entire organization can also be
developed or purchased. Many organizations are turning to
enterprise resource planning software, a set of integrated
programs that manage a company's vital business operations
for an entire multisite, global organization.
Three approaches to developing application software are
to build proprietary application software, buy existing pro-
grams off the shelf, or use a combination of customized and
off-the-shelf application software. Building proprietary soft-
ware (in-house or on contract) has the following advantages:
The organization will get software that more closely matches
