5 Information Systems Software

Chapter 5

Information Systems Software

5.1 Software Overview

Computer hardware is virtually useless without computer
software. Software is the programs that are needed to accomplish the input, processing,
output, storage, and control activities of information systems.

Computer software is typically classified into two
major types of programs: system software and application software.

System Software

Systems software are programs that manage the
resources of the computer system and simplify applications programming. They include
software such as the operating system, database management systems, networking software,
translators, and software utilities.

Application Software

Application software are programs that direct
the performance of a particular use, or application, of computers to meet the information
processing needs of end users. They include Aoff-the-shelf@ software such as word processing and spreadsheet
packages, as well as internally or externally developed software that is designed to meet
the specific needs of an organization.

Software trends have been away from custom-designed
one-of-kind programs developed by the professional programmers or end users of an
organization toward the use of Aoff-the-shelf@ software packages acquired by end users from
software vendors.

Two types of packages are available:

1. Vertical packages – assist
users within a specific industry segment. Examples include packages that help to manage
construction projects, keep track of inventory of hospitals, or fast-food outlets.

2. Horizontal packages – can
perform a certain general function, such as accounting, or office automation, for a range
of businesses.

Relationships between Hardware and Software Components
[Figure 5.1][Slide 5-3]

Figure 5.1 is an excellent tool to use to explain
the relationship that exists between computer systems hardware, systems software, and
application software. This Aonion-skin@ model indicates that the outer layers rely on the
facilities furnished by the inner ones.

5.2 Operating Systems

The most important system software package for any
computer is its operating system. Every computer system runs under the control of an
operating system. Operating systems for computers that are shared by many users are
considerably more complex than operating systems for personal computers.

What Does an Operating System Do?

The operating system is the software that
controls all the resources of a computer system. For example it:

1. Assigns the needed
hardware to programs

2. Schedules programs for
execution on the processor

3. Allocates the memory
required for each program

4. Assigns the necessary
input and output devices

5. Manages the data and
program files stored in secondary storage

6. Maintains file
directories and provides access to the data in the files

7. Interacts with the users

 

Multiprogramming is the capacity of a computer
to executing several programs concurrently on the same processor by having one of the
programs using the processor while others are performing input or output.

Multiprogramming requires that the active parts of the
programs competing for the processor be available in main memory. Virtual memory
is the seemingly expanded capacity of the main memory of the computer, and achieved by
keeping in the main memory only the immediately needed parts of programs, with the
complete programs kept in secondary storage.

Modes of Computer System Operation

Operating systems enable the system they manage to
operate in various modes. These include batch processing, time sharing, and real-time
processing.

Batch processing Processing programs or
transactions in batches, without a user’s
interaction.

Time Sharing Systems providing interactive
processing by allocating a short time slice for the use of the server to each user in
turn.

Real-time Processing Systems that respond to an
event within a fixed time interval; used for example, in manufacturing plants or to
collect data from several pieces of equipment in a laboratory.

With the move toward multiprocessors, in which several
(or even many) processors are configured in a single computer system, multiprocessing
operating systems have been designed to allocate the work to the multiple processors.
These systems also support multiprogramming, which allows many programs to compete for the
processors.

Operating Systems for Personal Computers

The operating systems of personal computers which are
dedicated to a single user are vastly simpler than the operating systems running larger
machines, to which hundreds or thousands of users may have simultaneous access. One
important capability an operating system can offer in a personal computing environment is multitasking:
the ability to run several tasks at once on behalf of a user.

The most popular microcomputer operating systems are:

Windows 95 – Windows 95 is an advanced operating system

– graphical user interface

– true multitasking

– network capabilities

– multimedia

DOS – is an older operating system which was used on
microcomputers

– is a single user, single-tasking operating system

– can add a GUI interface and multitasking capabilities
by using an operating environment such as Microsoft Windows

OS/2 Warp – graphical user interface

– multitasking

– virtual memory capabilities

– telecommunications capabilities

Windows NT – multitasking network operating system

– multiuser network operating system

– installed on network servers to manage local area
networks with high-performance computing requirements

UNIX     – popular operating system
that is available for micros, minis, and mainframe computer systems

– multitasking and multiuser system

– installs on network servers

MacIntosh System 7 – multitasking

– virtual memory capabilities

– graphical user interface

User Interface

A user interface is a combination of means by which a
user interacts with the computer system. It allows the end user to communicate with the
operating system so they can load programs, access files, and accomplish other tasks. The
three main types of user interfaces are:

1. Command drive

2. Menu drive

3. Graphical User Interface
(GUI)

The most popular graphical user interface is that
provided by Windows 95. The Windows environment has become a standard platform for
computers.

The Goal of Open Systems

A drive is to use open systems in organizational
computing, so that the software and hardware of any vendor can operate with those of any
other, calls for an operating system that would run on any hardware platform. The term Aopen system@
is used as the opposite of proprietary systems of a specific manufacturer.

In open systems, organizations want portability,
scalability, and interoperability of applications software.

Portable application: can be moved from one computer
system to another.

Scalable application: is one that can be moved without
significant reprogramming.

Interoperability: means that machines of various
vendors and capabilities can work together to produce needed information.

5.3 Personal Productivity Software

Personal productivity software is the most common
applications software. Run on personal computers, these programs assist the user in a
certain range of tasks. Taken together with professional support systems and systems
supporting groupwork, personal productivity software is a potent enabler of today’s
knowledge work.

Functions of Personal Productivity Software [Figure
5.3][Slide 5-4]

Personal productivity software enhances its
user’s performance on a specific range of common tasks. This software supports database
management and analysis, authoring and presentation, and activity and notes tracking. All
these are software applications. Data management is supported by database management
systems, while spreadsheet software assists in data analysis. For the needs of authoring
and presentation, users employ the applications software for word processing, desktop
publishing, presentation, and multimedia authoring. Personal information management
software is used to track activities and personal notes. Communications software enables
the user to connect to a telecommunications network in order to exchange information with
other users or systems. Web browsers are used to access the resources of the Internet’s
World Wide Web.

Spreadsheets

Electronic spreadsheet packages are programs
that are used for analysis, planning, and modelling. They provide electronic replacement
for more traditional tools such as paper worksheets, pencils, and calculators. In a
worksheet of rows and columns are stored in the computer’s memory and displayed on the
video screen. Data and formulas are entered into the worksheet and the computer performs
the calculations based on the formulas entered. A spreadsheet package can also be used as
a decision support tool to perform what-if analysis.

Database Management

Database management packages facilitate the
storage, maintenance, and utilization of data in a database that is shared by many users.
Microcomputer DBMs enables the users to:

1. Create and maintain a
database

2. Query a database with a
query language

3. Prepare formatted
reports

In addition, packages offer security features, network
connectivity, and the ability to present graphical output, as well as to perform
spreadsheet-type computations.

Word Processing

Word processing packages are programs that
computerize the creation, edition, and printing of documents by electronically processing
text data. Word processing is an important application of office automation. Word
processing is the most popular authoring and presentation activity. In fact, it is the
most common personal computing application.

Desktop Publishing

Organizations use desktop publishing software to
produce their own printed materials like newsletters, brochures, manuals, and books with
several type styles, graphics, and colors on each page. The components required to set up
a modest desktop publishing system include: a high-resolution display, a laser printer,
desktop publishing software, and perhaps a scanner.

Presentation Software

The goal of presentation graphics is to provide
information in a graphical form that helps end users and mangers understand business
proposals and performance and make better decisions about them. It is important to note
that presentation graphics does not replace reports and displays of numbers and text
material.

Multimedia Authoring Software

Multimedia authoring software enables its users
to design multimedia presentations. Using these packages, you can develop attractive
computer-based training (CBT) courseware or customer presentations. This software has
superior graphic imagery, computer animation, and motion video which may be combined with
high-fidelity sound in combination with the text.

Hypermedia are electronic documents that
contain multiple forms of media, including text, graphics, video, voice messages, or other
units of information such as worksheets. In the hypermedia method of information delivery,
linkages may be established among various items in a large multimedia document. These
linkages enable the user to move from one topic directly to a related one, instead of
scanning the information sequentially. Hypertext is a methodology for the construction and
interactive use of text databases. By definition, hypertext contains only text and a
limited amount of graphics.

Personal Information Management

Personal Information management (PIM) packages
are tools that help knowledge workers track tasks, people, projects, commitments, and
ideas. These packages help end users store, organize, and retrieve text and numerical data
in the form of notes, lists, clippings, tables, memos, letters, reports, and so on.

Communications Software and Web Browser

Communications software enables the user to
connect to a telecommunications network in order to exchange information with other users
or systems. The software provides the following capabilities:

1. Sending and receiving
electronic mail

2. File transfer. You can
download a program or a data file from a remote computer to your own workstation or upload
a file to the remote computer.

3. Terminal emulation –
enabling the personal computer to act as a terminal when required in a particular
application.

4. Sending and receiving a
fax

More and more frequently, the reason for connecting to
a telecommunications network is to gain access to the resources of the Internet. Web
browsers are rapidly becoming one of the most popular categories of software packages. A browser
is a program that enables its user to access electronic documents in included in the
Internet’s World Wide Web, a collection of interlinked hypermedia databases distributed
among remote sites.

5.4 Programming Languages and their Translators
[Figure 5.8][Slide 5-5]

Much of the applications software used in an
organization needs to be programmed or customized. Programming languages are the languages
which computer programs are written int. A programming language allows a programmer or end
user to develop the sets of instructions that constitute a computer program. These
languages have evolved over four generations and can be grouped into five major
categories:

1. Machine languages

2. Assembler languages

3. High-level languages

4. Fourth generation
languages

5. Object-oriented
languages

Machine Languages:

Machine languages are the most basic level of
programming languages. They were the first generation of machine languages.

Disadvantages of machine languages:

1. Programs had to be written using binary codes
unique to each computer.

2. Programmers had to have a detailed knowledge of the
internal operations of the specific type of CPU they were using.

3. Programming was difficult and error-prone

4. Programs are not
portable to other computers.

 

Assembler Languages:

Assembler languages are the second generation of
machine languages. They were developed to reduce the difficulties in writing machine
language programs. Assembly language is also a low-level language (refers to machine
resources, such as registers and memory addresses), it is also specific to a computer
model or a series of models.

An assembly language program is translated into a
machine language by a simple translator called an assembler. Assembly
languages are used today only when tight control over computer hardware resources is
required, such as in certain systems programs, particularly those for real-time computing.

Advantages:

1. Uses symbolic coded instructions which are
easier to remember

2. Programming is simplified as a programmer does not
need to know the exact storage location of data and instructions.

3. Efficient use of
computer resources is outweighted by the high costs of very tedious systems development
and by lock of program portability.

Disadvantage:

1. Assembler languages are unique to specific types
of computers.

2. Programs are not
portable to other computers.

High-Level Languages (procedural)

High-level languages are the third generation
programming languages. These languages provide statements, each of which is translated
into several machine-language instructions. High-level languages include COBOL (business
application programs), BASIC (microcomputer end users), FORTRAN (scientific and
engineering applications), and more popular today are C, C++, and Visual Basic.

Advantages:

1. Easier to learn and understand than an assembler
language as instructions (statements) that resemble human language or the standard
notation of mathematics.

2. Have less-rigid rules, forms, and syntaxes, so the
potential for error is reduced.

3. Are machine-independent programs therefore programs
written in a high-level language do not have to be reprogrammed when a new computer is
installed.

4. Programmers do not have to learn a new language for
each computer they program.

 

Disadvantages:

1. Less efficient than assembler language programs
and require a greater amount of computer time for translation into machine instructions.

 

Beyond High-Level Programming Languages

The fourth-generation languages (4GLs) specify what
needs to be done rather than detailing steps to doing it. 4GLs include a variety of
programming languages that are more nonprocedural and conversational than prior languages.

Advantages:

1. Simplified the programming process.

2. Use nonprocedural languages that encourage users and
programmers to specify the results they want, while the computers determines the sequence
of instructions that will accomplish those results.

3. Use natural languages that impose no rigid
grammatical rules

Disadvantages:

1. Less flexible that other languages

2. Less efficient (in terms of processing speeds and
amount of storage capacity needed).

A number of languages could lay claim to belonging to
the fifth generation. The following types of programming languages are likely to influence
the development of such a new paradigm:

1. Object-oriented
programming (OOP) languages tie data elements and the procedures or actions that will be
performed on them, together into objects. Examples include Smalltalk, C++, Visual Basic,
Java, Turbo C++, C++, Object C+

2. Languages that
facilitate parallel processing in systems with a large number of processors.

3. Functional languages
(such as LISP), based on the mathematical concept of computation as an application of
functions.

4. Limited subsets of
natural languages which can be processed thanks to the progress in artificial
intelligence.

Advantages:

1. OOP languages are easier to use and more
efficient for programming the graphics-oriented user interface required by many
applications.

2. Programmed objects are reusable.

Translators: Compilers and Interpreters

A variety of software packages are available to help
programmers develop computer programs. For example, programming language translators are
programs that translate other programs into machine language instruction codes that
computers can execute. Other software packages called programming tools help programmers
write programs by providing program creation and editing facilities. Language
translator programs (language processors) are programs that translate other programs into
machine language instruction codes the computer can execute. These programs allow you to
write your own programs by providing program creation and editing facilities.

Programming language translator programs are known by a
variety of names.

Assembler: translates the symbolic instruction
codes of programs written in an assembler language into machine language instructions.

Compiler: translates (compiles) high-level language
statements (source programs) to machine language programs.

Interpreter: translates and executes each program
statement one at a time, instead of first producing a complete machine language program,
like compilers and assemblers do.

5.5 Fourth-Generation Languages: (4GL’s)

4GL’s include a variety of programming languages that
are more nonprocedural and conversational than prior languages. The use of
fourth-generation languages permits a severalfold increase in productivity in information
systems development.

Categories of Fourth-Generation Languages and their
Role in End-User Computing

The distinguishing feature of 4GLs is that they specify
what is to be done rather than how to do it. Characteristics of 4GL’s
include:

1. The languages are
nonprocedural

2. They do not specify the
complete procedure for accomplishing the task (this is filled in by the software
translator for the 4GL).

3. About one-tenth of the
number of instructions are required in 4GL as compared to procedural languages. [Figure
5.12]

4. Principal categories of
4GLs are query languages, report generators, and application generators – Figure 5.13
[Slide 5-6]

5. Query languages and
report generators make it unnecessary to develop certain applications by providing direct
access to a database. Application generators make it relatively easy to specify in
nonprocedural terms a system for such access.

6. 4GLs also have software
generators for producing decision support and executive information systems.

Three categories of 4GLs are:

1. Query language

2. Report generators

3. Application generators

Query Languages

Query languages enable end users to access databases
directly. Characteristics of query language include:

1. Used online for ad-hoc
queries, that is, queries that are not predefined

2. Result of the query is
generally not formatted since it is displayed in a default format selected by the system
itself.

3. Interaction is usually
simple, only very simple computations are involved.

4. Most query languages
also make it possible to update databases. With many query languages, it is possible to
request a graphical output to a query.

Six primary styles for querying a database:

1. Form fill-in

2. Menu selection

3. Command-type query
language, such as SQL

4. Query by example (QBE)

5. Direct manipulation

6. Restricted natural
language

Query languages are appropriate for:

1. Automatic teller
machines

2. Electronic kiosks

Report Generators

A report generator enables an end user or an
information systems professional to produce a report without detailing all the necessary
steps, such as formatting the document.

Characteristics of report generators include:

1. Offer users greater
control over the content and appearance of the output than a query language.

2. Specified data may be
retrieved from the specified files or databases, grouped, ordered, and summarized in a
specified way, and formatted for printing as desired.

Application Generators

An application generator makes it possible to specify
an entire application, consisting of several programs, without much detailed coding.
Characteristics of application generators include:

1. Most generators produce
(generate) code in a procedural language. This code may then be modified to meet the
precise needs of the application.

2. Generators targeted
toward end users are simple to use. They are targeted to a limited application domain.
They produce the code mostly from a specification of the structure of files and databases
and from the given layouts of screens and reports. The requisite processing is specified
in terms natural to the end users.

3. A screen-painting
facility makes it possible to specify the graphical user interface for the system under
development.

4. Powerful application
generators require the expertise of information systems professionals, and are
general-purpose tools. They often may run on mainframes and minicomputers.

5. Application generators
are increasingly integrated into computer-aided software engineering (CASE) environments.

 

Advantages:

1. Simplified the programming process.

2. Use nonprocedural languages that encourage users and
programmers to specify the results they want, while the computers determines the sequence
of instructions that will accomplish those results.

3. Use natural languages that impose no rigid
grammatical rules

 

Disadvantages:

1. Less flexible that other languages

2. Programs written in 4GLs are generally far less
efficient during program execution that programs in high-level languages. Therefore, their
use is limited to projects that do not call for such efficiency.

 

5.6 Object-Oriented Languages

The idea of object-oriented programming (OOP) is to
build programs of software objects, in order to tie data elements and the procedures or
actions that will be performed on them, together into objects. Examples include Smalltalk,
C++, Turbo C++, Object C+, Java.

Characteristics of OOP include:

1. OOP, objects combine
(encapsulate) the data with the operations that act on the data.

2. OOP support class
definition and inheritance, creating objects as instances of classes, sending messages to
the methods in these objects during program execution, and other features of OOP.

3. OOP simplifies design of
multimedia systems and of graphical user interfaces.

Three fundamental concepts of object-oriented
programming are:

1. Objects

2. Classes

3. Inheritance

Objects: are the basic components of which programs are
built. In software, a program component that models a real-world object by encapsulating
data and instructions that work with these data.

Class: is a template from which objects are created.
Classes can be defined in a hierarchy.

Inheritance: in object-oriented programming, classes
lower in the hierarchy inheriting properties (attributes and methods) of the classes
higher in it.

Advantages:

1. OOP languages are easier to use and more
efficient for programming the graphics-oriented user interface required by many
applications.

2. Saves much programming, since inheriting properties
means programmed objects are reusable.