Chapter 5

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.

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 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.

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 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 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 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 (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 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.

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.

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.

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.

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.

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.

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

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.

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.

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

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.

 

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.

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.