Information Systems Software
5.1 Software Overview
Computer hardware is virtually useless without computersoftware. 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 twomajor types of programs: system software and application software.
System Software
Systems software are programs that manage theresources of the computer system and simplify applications programming. They includesoftware such as the operating system, database management systems, networking software,translators, and software utilities.
Application Software
Application software are programs that directthe performance of a particular use, or application, of computers to meet the informationprocessing needs of end users. They include Aoff-the-shelf@ software such as word processing and spreadsheetpackages, as well as internally or externally developed software that is designed to meetthe specific needs of an organization.
Software trends have been away from custom-designedone-of-kind programs developed by the professional programmers or end users of anorganization toward the use of Aoff-the-shelf@ software packages acquired by end users fromsoftware vendors.
Two types of packages are available:
1. Vertical packages - assistusers within a specific industry segment. Examples include packages that help to manageconstruction projects, keep track of inventory of hospitals, or fast-food outlets.2. Horizontal packages - canperform a certain general function, such as accounting, or office automation, for a rangeof businesses.Relationships between Hardware and Software Components[Figure 5.1][Slide 5-3]
Figure 5.1 is an excellent tool to use to explainthe relationship that exists between computer systems hardware, systems software, andapplication software. This Aonion-skin@ model indicates that the outer layers rely on thefacilities furnished by the inner ones.
5.2 Operating Systems
The most important system software package for anycomputer is its operating system. Every computer system runs under the control of anoperating system. Operating systems for computers that are shared by many users areconsiderably more complex than operating systems for personal computers.
What Does an Operating System Do?
The operating system is the software thatcontrols 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 computerto executing several programs concurrently on the same processor by having one of theprograms using the processor while others are performing input or output.
Multiprogramming requires that the active parts of theprograms competing for the processor be available in main memory. Virtual memoryis the seemingly expanded capacity of the main memory of the computer, and achieved bykeeping in the main memory only the immediately needed parts of programs, with thecomplete programs kept in secondary storage.
Modes of Computer System Operation
Operating systems enable the system they manage tooperate in various modes. These include batch processing, time sharing, and real-timeprocessing.
Batch processing Processing programs ortransactions in batches, without a user'sinteraction.
Time Sharing Systems providing interactiveprocessing by allocating a short time slice for the use of the server to each user inturn.
Real-time Processing Systems that respond to anevent within a fixed time interval; used for example, in manufacturing plants or tocollect 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, multiprocessingoperating systems have been designed to allocate the work to the multiple processors.These systems also support multiprogramming, which allows many programs to compete for theprocessors.
Operating Systems for Personal Computers
The operating systems of personal computers which arededicated to a single user are vastly simpler than the operating systems running largermachines, to which hundreds or thousands of users may have simultaneous access. Oneimportant 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 onmicrocomputers
- 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 systemthat 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 auser interacts with the computer system. It allows the end user to communicate with theoperating system so they can load programs, access files, and accomplish other tasks. Thethree main types of user interfaces are:
1. Command drive 2. Menu drive 3. Graphical User Interface (GUI)
The most popular graphical user interface is thatprovided by Windows 95. The Windows environment has become a standard platform forcomputers.
The Goal of Open Systems
A drive is to use open systems in organizationalcomputing, so that the software and hardware of any vendor can operate with those of anyother, 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 computersystem to another.
Scalable application: is one that can be moved withoutsignificant reprogramming.
Interoperability: means that machines of variousvendors and capabilities can work together to produce needed information.
5.3 Personal Productivity Software
Personal productivity software is the most commonapplications software. Run on personal computers, these programs assist the user in acertain range of tasks. Taken together with professional support systems and systemssupporting groupwork, personal productivity software is a potent enabler of today'sknowledge work.
Functions of Personal Productivity Software [Figure5.3][Slide 5-4]
Personal productivity software enhances itsuser's performance on a specific range of common tasks. This software supports databasemanagement and analysis, authoring and presentation, and activity and notes tracking. Allthese are software applications. Data management is supported by database managementsystems, while spreadsheet software assists in data analysis. For the needs of authoringand presentation, users employ the applications software for word processing, desktoppublishing, presentation, and multimedia authoring. Personal information managementsoftware is used to track activities and personal notes. Communications software enablesthe user to connect to a telecommunications network in order to exchange information withother users or systems. Web browsers are used to access the resources of the Internet'sWorld Wide Web.
Spreadsheets
Electronic spreadsheet packages are programsthat are used for analysis, planning, and modelling. They provide electronic replacementfor more traditional tools such as paper worksheets, pencils, and calculators. In aworksheet of rows and columns are stored in the computer's memory and displayed on thevideo screen. Data and formulas are entered into the worksheet and the computer performsthe calculations based on the formulas entered. A spreadsheet package can also be used asa decision support tool to perform what-if analysis.
Database Management
Database management packages facilitate thestorage, 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, networkconnectivity, and the ability to present graphical output, as well as to performspreadsheet-type computations.
Word Processing
Word processing packages are programs thatcomputerize the creation, edition, and printing of documents by electronically processingtext data. Word processing is an important application of office automation. Wordprocessing is the most popular authoring and presentation activity. In fact, it is themost common personal computing application.
Desktop Publishing
Organizations use desktop publishing software toproduce their own printed materials like newsletters, brochures, manuals, and books withseveral type styles, graphics, and colors on each page. The components required to set upa 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 provideinformation in a graphical form that helps end users and mangers understand businessproposals and performance and make better decisions about them. It is important to notethat presentation graphics does not replace reports and displays of numbers and textmaterial.
Multimedia Authoring Software
Multimedia authoring software enables its usersto design multimedia presentations. Using these packages, you can develop attractivecomputer-based training (CBT) courseware or customer presentations. This software hassuperior graphic imagery, computer animation, and motion video which may be combined withhigh-fidelity sound in combination with the text.
Hypermedia are electronic documents thatcontain multiple forms of media, including text, graphics, video, voice messages, or otherunits of information such as worksheets. In the hypermedia method of information delivery,linkages may be established among various items in a large multimedia document. Theselinkages enable the user to move from one topic directly to a related one, instead ofscanning the information sequentially. Hypertext is a methodology for the construction andinteractive use of text databases. By definition, hypertext contains only text and alimited amount of graphics.
Personal Information Management
Personal Information management (PIM) packagesare tools that help knowledge workers track tasks, people, projects, commitments, andideas. These packages help end users store, organize, and retrieve text and numerical datain the form of notes, lists, clippings, tables, memos, letters, reports, and so on.
Communications Software and Web Browser
Communications software enables the user toconnect to a telecommunications network in order to exchange information with other usersor 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 toa telecommunications network is to gain access to the resources of the Internet. Webbrowsers are rapidly becoming one of the most popular categories of software packages. A browseris a program that enables its user to access electronic documents in included in theInternet's World Wide Web, a collection of interlinked hypermedia databases distributedamong remote sites.
5.4 Programming Languages and their Translators[Figure 5.8][Slide 5-5]
Much of the applications software used in anorganization needs to be programmed or customized. Programming languages are the languageswhich computer programs are written int. A programming language allows a programmer or enduser to develop the sets of instructions that constitute a computer program. Theselanguages have evolved over four generations and can be grouped into five majorcategories:
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 ofprogramming 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 ofmachine languages. They were developed to reduce the difficulties in writing machinelanguage programs. Assembly language is also a low-level language (refers to machineresources, such as registers and memory addresses), it is also specific to a computermodel or a series of models.
An assembly language program is translated into amachine language by a simple translator called an assembler. Assemblylanguages are used today only when tight control over computer hardware resources isrequired, 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 generationprogramming languages. These languages provide statements, each of which is translatedinto several machine-language instructions. High-level languages include COBOL (businessapplication programs), BASIC (microcomputer end users), FORTRAN (scientific andengineering 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 whatneeds to be done rather than detailing steps to doing it. 4GLs include a variety ofprogramming 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 tothe fifth generation. The following types of programming languages are likely to influencethe 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 helpprogrammers develop computer programs. For example, programming language translators areprograms that translate other programs into machine language instruction codes thatcomputers can execute. Other software packages called programming tools help programmerswrite programs by providing program creation and editing facilities. Languagetranslator programs (language processors) are programs that translate other programs intomachine language instruction codes the computer can execute. These programs allow you towrite your own programs by providing program creation and editing facilities.
Programming language translator programs are known by avariety of names.
Assembler: translates the symbolic instructioncodes of programs written in an assembler language into machine language instructions.
Compiler: translates (compiles) high-level languagestatements (source programs) to machine language programs.
Interpreter: translates and executes each programstatement 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 thatare more nonprocedural and conversational than prior languages. The use offourth-generation languages permits a severalfold increase in productivity in informationsystems development.
Categories of Fourth-Generation Languages and theirRole in End-User Computing
The distinguishing feature of 4GLs is that they specifywhat is to be done rather than how to do it. Characteristics of 4GL'sinclude:
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 databasesdirectly. 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 aninformation systems professional to produce a report without detailing all the necessarysteps, 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 specifyan 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 tobuild programs of software objects, in order to tie data elements and the procedures oractions 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-orientedprogramming are:
1. Objects 2. Classes 3. Inheritance
Objects: are the basic components of which programs arebuilt. In software, a program component that models a real-world object by encapsulatingdata 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, classeslower in the hierarchy inheriting properties (attributes and methods) of the classeshigher 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.
