Unit 1 SYSTEM DEVELOPMENT CONCEPT

Unit 1: SYSTEM DEVELOPMENT CONCEPT

Information System

The word 'system' is widely used. It has become fashionable to attach the word 'system' to add a contemporary flair when referring to things or processes. People speak of exercise systems, investment systems, delivery systems and information systems. In terms of computer, in this section, we will discuss general system's concepts of analyzing and designing information systems.

The word 'system' is derived from the Greek word system, which means an organized relationship among the functioning units or components. In our daily life, we come into contact with transposition of a system, the communication system, the accounting system, the production system, the economic system and the computer system for over three decades. We are more concerned with computer systems.

Note: An information system is an organized combination of people, hardware, software, communication networks and data resources that collects, transforms and disseminates information in an organization.

A system can be categorized into the following groups.

·         Physical or abstract systems

The physical system is tangible entities that may be static or dynamic, e.g. building whereas the abstract system is conceptual entity, e.g. company.

·         Open or closed systems

An open system is a system which continuously interacts with its environment. The interaction can take the form of information, energy or material transfers into or out of the system boundary, depending on the discipline which defines the concept. An open system should be contrasted with the concept of an isolated system which exchanges neither energy, matter nor information with its environment.

A closed system refers to software in which the specifications and detail of implementation (typically source code) are kept secret, as opposed to open source system.

·         Deterministic or probabilistic systems

A deterministic system is a conceptual model of the philosophical doctrine of determinism, applied to a system for understanding everything that has and will occur in the system, based on the physical outcomes of causality. In a deterministic system, every action or cause, produces a reaction or effect and every reaction, in turn, becoming the cause of subsequent reactions.

A deterministic system has a single result or a set of results given a set of input parameters, while a probabilistic system will have results that vary. Often, a probabilistic system (also called stochastic model, process or system) is solved with the Monte-Carlo method. In this case, a computer program uses a pseudo-random number generator to provide values of the attributes in the system, which may vary.

The program provides an assessment of the uncertainty of results. Typically, a large number of runs (also called trials or iterations) are made. Summary statistics may include the value that occurs most frequently (mode), the mean value, and low and high range, for instance, the 10% and 90% percentile. The standard deviation and histogram of results may also be part of the summary information. There is no single standard presentation as this will depend on the application.

The alternative Monte-Carlo methods are to solve the problems using the mathematics of probability. This can be very complicated to do in some cases. Monte-Carlo method is available in Excel as functions. For example, and between () for uniform discrete distribution and rand () for uniform continuous distribution from 0.

·         Man-made information systems

The systems developed and engineered by human are a man-made system. In this section, we are more concerned about man-made information systems, which are further classified as:

1. Formal Information System

This system defines very clearly about the workflow system, communication flow-down, and the authority. The information flows in terms of policies, goals, strategies, rules and regulations from the top level management to the bottom level of management. The information also flows from the bottom level management to the top level in terms of feedback, results of work done, etc.

2. Informal Information System

The informal information system should be employee based and cater to their development and solve their work related problem. Employee co-operation and the knowledge of the informal communication should help one to get good informal information systems in place.

3. Computer-based Information system

The third category of an information system depends mainly on the computer for handling business applications. System analysts develop several different types of information system to meet a variety of business needs. There is a class of systems collectively known as Computer Based Information Systems.

As we have different types of transportation system such as highway systems, railway systems, and airline systems; computer-based information systems are also of too many types. They are classified as:

1.     Transaction Processing Systems (TPS)
A Transaction Process System (TPS) is a type of information system that collects, stores, modifies and retrieves the data transaction of an enterprise. A transaction is any event that passes the ACID (Atomicity, Consistency, Isolation, and Durability) test in which data is generated or modified before storing in an information system.

2.     Management Information System (MIS)
A Management Information System (MIS) is a system or process that provides the information necessary to manage an organization effectively. MIS and the information it generates are generally considered essential components of prudent and reasonable business decisions.

3.     Decision Support Systems (DSS)
Decision Support System (DSS) is computerized information system that helps in the decision-making process of an organization. In other words, DSS are a specific class of computerized information system that supports business and organizational decision-making activities.It helps to analyze the business information and data for making better and suitable decisions.

4.     Office Automation Systems (OAS)
Office automation refers to the varied computer machinery and software used to digitally create, collect, store, manipulate and relay information needed to office for accomplishing basic tasks and goals. Raw data storage, electronic transfer and the management of electronic business information comprise the basic activities of an office automation system. Office automation helps in optimizing or automating existing office procedures. The backbone of office automation is a LAN, which allows users to transmit data, mail and even voice across the network.

Sub System and Super System

Every system except the super system is a part of larger system. The super system contains all the other systems. Since every system is a part of larger system, it is also a subsystem of the larger system. For example, a sales department is a sub-system of an organization. In larger systems, each sub-system is interlinked and forms closed deterministic system.

System Study

The system study may be defined as a study of the operations of a set of connected elements and of the interconnections between these elements. It is a step-by-step process used to identify and then develop specific improvements in an organization's information system. It shows clearly that one cannot ignore any part or element of a system without first finding out the effect that element has on the operation of the system as a whole.

System is a collection or arrangement of entities or things, related or connected in such a way that they form a unity on the whole. In system, the entities are designed and controlled by people, the entities are generally arranged so that they interact to accomplish one or more objectives. For example, the entities of an educational system consist of students, faculty, administrators, textbooks, buildings, equipment and many other entities. The entities of the system interact (e.g. faculty teach students, students read textbooks, administrators schedule classroom facilities), and ultimately, the primary objective of the system, learning is accomplished. Anything external to the system is referred to as the environment of the system.In any system, a number of entities are interrelated. The following transformation process exemplifies the interwoven relationships among many entities.

INTRODUCTION TO SYSTEM ANALYST

Information system analysts are people who are involved in analyzing, designing, implementing and evaluating computer-based information systems to support the decision making activities and operations of an organization. They are ostensibly a boundary spanner between computers and management as illustrated in the following circle graph.

As the graph shows, system analysts must understand the technology, the organization and the skill of their trade. To refine this future, the key ingredients that makes a good system analyst are:

1.     Understanding and commitment to the organization

2.     People skills

3.     Conceptual skills and

4.     Technical skills

A system analyst is information specialist. To be a system analyst, one must be knowledgeable about the technical aspects of analyzing, designing and implementing computer-based systems. A system analyst is a person who conducts a study, identifies activities and objectives and determines a procedure to achieve the objectives.

Designing and implementing systems to suit organizational needs are the functions of the systems analyst. One plays a major role in seeing the business benefits from computer technology. An analyst is a person with unique skills. One uses these skills to coordinate the efforts of different types of persons in an organization to achieve business goals.

Responsibility of System Analyst

A system analyst carries out the following jobs:

·         The first and perhaps the most difficult task of system analyst is problem definition. Business problems are quite difficult to define. It is also true that problems cannot be solved until they are precisely and clearly defined.

·         Initially, a system analyst does not know how to solve a specific problem. One must consult managers, users and other data processing professionals in defining problems and developing solutions. One uses various methods for data gathering to get the correct solution of a problem.

·         Having gathered the data relating to problems the system analyst analyzes those data and thinks of the plan to solve it. One may not come up personally with the best way of solving a problem but pulls together other people’s ideas and refines them until a workable solution is achieved.

·         Systems analyst coordinates the process of developing solutions. Since, many problems have a number of solutions, the system analyst must evaluate the merit of such proposed solution before recommending one to the manager.

·         System analysts are often referred to as planners. A key part of the system analyst job is to develop a plan to meet the management objectives.

·         When the plan has been accepted, a system analyst is responsible for designing it so that management’s goal could be achieved. System design is time-consuming, complex and requires precise task.

·         System must be thoroughly tested. The system analyst often coordinates the testing procedures and helps in deciding whether or not the new system is meeting standards established in the planning phase.

Characteristics of System Analyst

·         Knowledge of People:Since, a system analyst works with others so closely, he or she must understand their needs and what motivates them to develop systems properly.

·         Knowledge of Business Function:A system analyst must know the environment in which he or she works. One must be aware of the peculiarities of management and the users at this installation and realize how they react to systems analysis. A working knowledge of accounting and marketing principles is a must since so many systems are built around these two areas. One must be familiar with one’s company’s product and services and management’s policies in areas concerning them.

·         Knowledge of Data processing Principles:Most systems today are computer based. The system analyst must be fully aware about the potential and limitations of computers.

·         Ability to Communicate:As a coordinator, a system analyst must communicate properly with people of different levels within an organization. A system analyst must listen carefully to what others say and integrate the thoughts of others into the system's development process.

·         Flexibility:System analysts must be flexible in their thinking and they often do not get their own way. Different fractions in an organization have conflicting needs and most systems are the result of compromise. The analyst’s goal is to produce the system that will be the best for this organization. This requires an open mind and flexibility in one’s ideas.

·         An Analytical Mind:It takes an unusual person to see through problems facing by an organization and develop solutions that will work. System analysts often find themselves with more data than they can cope with. It requires an analytical mind to select pertinent data and concentrate on them in defining problems and forming solutions.

·         Well Educated with Sharp Mind:Systems analyst is called upon to work with people at all levels virtually in every aspect of business. They must know how to work with all of them and gain their confidence. Analysts must have the sharp mind to learn quickly how people do their jobs and develop ways for them to do it better.

# Specialization of Basic Data Processing Positions

In large software development project, various specialists are employed to solve problems of different nature. Targeting to different divisions, a number of system analysts work together. Various system analysts and their job descriptions are given below:

# Position Description

In the software development organizations, there are various positions and job descriptions. The basic data processing and information system personnel are as follows:

Development Personnel	Position Description
System Analyst	Analyzes, design, implements and evaluates computer-based processing systems to process transactions and provide informations to meet organizational requirements.
Programmer	Design codes tests and debugs computer programs which are consistent with systems design specifications.
Computer Operator	Monitors and controls the operations of computer equipment.
Data Entry Operator	Operator microprocessor terminal to directly enter data into a computer system.
Production Controller	Records, maintains and control information on the receipt and processing of a transaction, and the subsequent distribution of generated reports.

 

# Programming

It is necessary for a user to understand the mechanism of preparing the programs and how they differ from software that we use. A program is prepared using programming language. For writing a particular program or solution for a problem, the programmers choose a suitable programming language.

A programming language is set of codes for writing programs. It contains statements, commands, built-in functions, data declaration mechanisms, repetition mechanism, giving an output of processing and much more that makes it a programming language.

# Characteristics of Good Programming

Now, we have come to know how the program should look like and how it could be prepared. We also discussed various methods of development programs. But, for a long programmer, a program must be very effective. A good program possesses the following characteristics:

1.     It should be portable. It means the software can support various platforms.

2.     It should be easily understandable by the users and must form the menu driven system.

3.     It should be very efficient in calculations and use.

4.     It should be structural. Various programs should have been broken into separate programs.

5.     It should be flexible so that small changes which are necessary could be made by writing small module instead of writing an entire program.

6.     The program should be documented at the user level and programmer level in easily understandable language.

# System Development Life Cycle (SDLC)

System Development Life Cycle (SDLC), which is also known as Application Development Life Cycle, is a term used in system that describes the process of planning, creating, testing and deploying an information system.

All organizations have several types of information systems. At any point of time, varying degrees of these information systems may be computer based. For example, an organization’s payroll information system may be computer based, but its strategic planning information system may be processed manually.As the time passes, organizational processes change. The organization’s information systems must change in response to the changing needs of an organization. When this occurs, management usually initiates some form as systems development life cycle (SDLC) to address the problem.

# System Development Life Cycle Models

During software development or system development for organizations, a common process framework is established, defining a small number of framework activities that are applicable to all software projects, regardless of their size complexity. For a better paradigm of a software process, several models are designed and implemented. It is the choice of system analyst which model is used to achieve the goal. The different models are:

·         Linear Sequential Model or Classic or Waterfall Model

We are going to discuss waterfall model or linear sequential or classic mode in this section. The original waterfall model was proposed by Winston Royce. Although, it made provisions for feedback loops, the vast majority of an organization that applies this process model treats it as if it was strictly linear. The various steps are illustrated by the following diagram.

·         Prototyping Model

The prototyping Model is a System Development Method (SDM) in which a prototype (an early approximation of final system or product) is built, tested and then reworked as necessary until an acceptable prototype is finally achieved from which the complete system or product can now be developed.

This model works best in scenarios where not all of the project requirements are known in detail ahead of time. It is an iterative, trial-and-error process that takes between the developers and the users.

·         Incremental Model

Incremental model is an evolution of waterfall model. The product is designed, implemented, integrated and tested as a series of incremental builds. It is a popular model software evolution used by many commercial software companies and system vendor.

Incremental software development model may be system vendor.

1.     Software requirements are well defined, but realization may be delayed.

2.     The basic software functionality is required early.

·         Spiral Model

The spiral model is a system development life cycle methodology that combines feature of prototyping with the waterfall methodology. The spiral model is often favored for large, complex projects.

Iterates cycle of these project phases:

1.     Requirements definition

2.     Risk analysis

3.     Prototyping

4.     Simulate, benchmark

5.     Design, implement, test

6.     Plan next cycle (if any)

Steps in the spiral model include:

1.     The new system requirements are defined. This usually involves interviewing a number of users representing all the end users of the system.

2.     A preliminary system design is created.

3.     An initial prototype of the new system is constructed from the preliminary design. This is usually a scaled-down system and represents an approximation of the final product’s characteristics.

4.     After evaluating the strengths, weaknesses and risks of the first prototype, a second prototype is developed and tested.

5.     If the risk considered is being too great, the client may choose to terminate the project at this point. Risk factors to be considered include development cost over runs, operating-cost miscalculations, etc.

6.     Subsequent prototypes are developed until the customer is satisfied, until the customer get assured that the latest prototype represents the desired product.

7.     The system is constructed based on the final prototype.

8.     The final system is evaluated and tested. Routine maintenance is carried out continually to prevent large-scale failures and to minimize downtime.

When to use Spiral Model

1.     When creating a prototype is appropriate.

2.     When costs and risk evaluation is important.

3.     For medium to high-risk projects

4.     Long –term project commitment unwise because of potential changes to economic priorities

5.     Users are unsure of their needs

6.     Requirements are complex

7.     New product line

8.     Significant changes are expected (research and exploration)

Since, there are possibilities of repetition in the system development as a new problem may arise. This situation can be represented diagrammatically below:

# New Problems or Opportunities Arise:

The initial step of system development cycle is the identification of new problems. In some cases, it can be considered as new opportunities. For example, a wholesale distributor receives customer complaints concerning late deliveries of goods. These late delivery result in loss of customer goodwill. The action is necessary to implement. To clearly understand the exact nature of the problem requires a thorough analysis and understanding of the existing system.

# Analyze and Document Existing Systems:

In the above example, the management may initiate a project team or task force to analyze the existing order-processing system. This project is headed by a team leader called system analyst. Analysis of the existing system consists:

1.     Review workflow

2.     Define decision making associated with workflow

3.     Review current information available to support decision-making

4.     Isolate deficiencies of the information system

# Design Information Requirements:

As soon as the deficiencies in the information system have been determined, solutions to those deficiencies can be designed. It is important that the solutions relate to improving workflow and the decisions being made must be related to the solutions. In other words, solutions should improve productivity.

# Design Technology and Personnel Requirements:

The design of information and processing requirements establishes the criteria for identifying alternative means for solution achievement. That is, the previous step defines what is desired. This step defines how to do it.

Variable technologies and personnel are identified that, if included in the system, it can be structured to support the solution defined in the previous step. Generally, several alternatives offering varying degrees of solution achievement are available.

# Develop, Test and Validate System:

At this point, the desired solutions and the means of achieving them have been identified. Specifically, inclusion and structure decisions are established for the information and technology of the new system. The actual structuring or development and testing of the system are now possible. This step consists of installing an additional hardware or software required and coding and testing computer programs where necessary.

# Implement System:

After a new system has been developed and tested, conversion from the old system to the new system is required. The actual implementation process can be expressed in terms of the continum that ranges from parallel to discrete. In a parallel system, the old and new systems are concurrently processed until the new system stabilizes. The parallel implementation reduces risk when implementing a new system.

# Evaluate and Maintain System:

After a new system has been implemented, it is important to review how effectively and efficiently the solutions to the new problems and opportunities have been achieved. Evaluation, therefore, consists of accessing the degree of variation between planned and actual system performance.

 

# SYSTEM DEVELOPMENT PROCEDURE

System development procedure is a process consisting of the major steps of system analysis and design. It starts when management or sometimes system development personnel felt that a new system or an improvement in the existing system is required.

The systems development lifecycle is classically thought of as the set of activities that analysts, designers and users carry out to develop and implement an information system. The System development life cycle consists of the following activities.

1.     Problem Definition ( Preliminary Investigation/Recognition)

2.     System Analysis (Determination of the System requirements)

3.     System Design

4.     Programming Analysis (Development of software)

5.     Program Preparation and Testing

6.     System Implementation

7.     System Evaluation

8.     System Maintenance

 

1. Problem Definition (Preliminary Investigation)

To create a new program of the system or to improve or modify an existing one, people have to recognize that a problem or need exists at the very beginning. This problem or need may result from changing operation conditions.

Managers, employees of departments are affected by changing conditions, and data processing personnel often participate in requirements sessions, until the problem has been defined and specified study goals have been outlining.

These goals should then be put in writing and approved by all concerned employees. This step cannot be bypassed. In this session, the requests are clarified and then, technical feasibility, economic feasibility, operational feasibility studies are made.

After a project request is approved, its cost, priority, completion time and personnel requirements are estimated and used to determine where to add it to any existing project list.

Problem definition is not a single task. It integrates various components which need to be detailed and processed using suitable tools. The major functional definitions include need technical feasibility, economical feasibility, behavioral feasibility study, etc.

2. System Analysis (Determination of the System Requirements)

After the users and specialists have identified the need for specific changes, a study team gathers and then analyzes data about current processing operations. At least one member usually represents (the person has a knowledge of the information needs) the departments affected by the study.

Another is a system analyst – Information specialist who’s knowledgeable about the technical aspects of analyzing, designing and implementing computer based processing systems. And a third may be an author who can see that proper accuracy and security controls are built into a new system. The following are the major issues of system analysis:

1.     Data collection

2.     Flow Chart preparation (a system study)

3.     Analyzing the findings.

At this level, the programmers, the designers and system analyst sit together and perform the major tasks such as entity analysis, functional analysis, preparing data flow diagram (DFD), designing data dictionary, etc. The major activities related to the system analysis is the feasibility study.

The details of feasibility studies are:

·         Technical Feasibility – determines whether project is technically feasible

·         Economical Feasibility – determines whether project is financially healthy

·         Operational Feasibility – determines whether the project can be operated successfully.

3. System Design

System design is the process of creating alternative solutions to satisfy the study goals, evaluating the choices and then drawing up the specifications for the chosen alternative. Design begins after the study team has analyzed the current procedure. Since, many factors have a bearing on the design process, it can be a challenging task.

It must be considered how changes made in one application department will affect related applications. After analyzing the current system and studying the flowchart, the study team prepares alternative way also. The job of the designers is to decide if the benefits and possible savings expected from design alternative outweigh the costs.

System analyst begins the design process by identifying reports and then other outputs system will produce. Then, the specific data on each are pinpointed. The system design also describes the data to be input, calculated or stored. Individual data items and calculation procedures are written in detail. Designers select file structures and storage devices, such as magnetic disk, magnetic tape, etc.

The procedures, they write say how to process the data and produce the output. Designers are responsible for providing programmers with complete and clearly outlined software specifications.

The system design is not a single task. The functional system design should have elaborative –Output design, Input design, Files design and storing mechanism inside the computer system, data and program processing and general program flow design.

4. Programming Analysis (Development of Software)

After top managers give their approval to create custom made software, the design specifications provide the input for the programming analysis phase of the study process. Programming analysis is the process of breaking down the design specification into the specific input/output, text manipulation/calculation, logic / comparison and storage/ retrieval operations which are required to satisfy the study goals.

Analysis tools such as program flowcharts (is the detailed program showing how individual processing steps will be performed within the computer to convert input data into the desired output) is used.

During programming analysis or software development phase, the programmers and designers prepare the flowcharts, write the pseudopodia in structured English and select the programming language for wiring the program code.

5. Program Preparation and Testing

The detailed input/output, text manipulation/ calculation, logic/ comparison, and storage/retrieval operations identified during the programming analysis stage provide the input for program preparation. One or more programmers concert these operations into a program of instruction written in a language and form acceptable to the computer hardware.

During system testing, the system is used experimentally to ensure that the software does not fail. In other words, we can say that it will run according to its specifications and in the way users expect. Especially, test data are input for processing and the results examined.

Before the program is delivered to the market, the system designers use the program in a virtual system which testifies the system and helps draw inferences for system conversion.

After the program preparation is completed, the new system must be checked for errors and tested before it can be used on a routine basis. When the software appears to be running properly, changeover is made. During this period, those who prepare input data and use output results must cooperate with data processing specialists if the new system is to be successful.

Finally, systems and programs, that have been successfully implemented are usually subject to continual change. A first class maintenance effort requires the co-operation of those people served by the system / program and those responsible for maintaining it. Of course, the need for a major change could trigger a new system study i.e. big change in current system evolves a new system.

Elimination of errors, adding modules, removing unnecessary modules, maker more user-friendly, etc. are some considerations of maintenance of a software product.

6. System Implementation

Implementation is the process of having systems personnel check out and put new equipment into use, train users, install the new application and construct any files of data needed to use it. This phase is less creative than system design.

Depending on the size of the organization that will be involved in using the application and the risk involved in its use, system developers may choose to test the operation in only one area of the firm with only one or two persons.

Sometimes, they will run both old and new system in a parallel way to compare the results. In still other situations, system developers stop using the old system one day and start using the new one the next.

7. System Evaluation

Evaluation of the system is performed to identify its strengths and weaknesses. The actual evaluation can occur along any of the following dimensions.

1.     Operational Evaluation

2.     Organizational Impact Evaluation

3.     User Manager Assessment Evaluation

4.     Development performance Evaluation

8. System Maintenance

Maintenance is necessary to eliminate errors in the working system during its working life and to tune the system to any variations in its working environment. Often small system deficiencies are found as a new system is brought into operations and changes are made to remove them.

From the above, we can conclude that the following steps determine the software development sequence.

 

# Concept of System Design Tools (Application Modeling Techniques)

System analysis can be complex and confusing work. The analyst should be able to deal with a large amount of highly detailed and often conflicting information. The analyst needs a way to organize the information, determine where there are gaps in understanding and identify areas of conflicting. Modeling techniques provide solutions for the system analyst.

The modeling techniques used in system development are:

• Context diagram
• Data Flow Diagram (DFD)
• E-R diagrams

 

Pseudo code and Algorithm

Programming Tools

During programming analysis and system design, the programmers, system engineers and system designers work together to build a successful program or a computer-based information system. Various ideas, components and program modules are integrated to accomplish the task.

System analysts and designers perform the following tasks during these steps.

1.     Selection of programming language

2.     Selection of the programming tools

3.     Design and virtual testing of the program.

The programming tools give the idea how the flow should take place in order to accomplish a task. Several programming tools are used in this context. Some of the most common programming tools are:

1.     Pseudo code

2.     Algorithm

3.     Flowchart

Pseudo code

Pseudo code is a combination of two words: Pseudo and Code. 'Pseudo' means imitation and 'code' refer to instruction written in the programming language. Pseudo code is not a real programming code. It is the generic way of describing an algorithm without using any specific programming language-related notations.

The features of pseudocode are:

·         It uses plain english statements.

·         It emphasizes on the design of the computer program.

·         It uses structured english.

·         It is detailed and readable to draw an inference.

·         It enables the programmers to concentrate on the algorithms.

The pseudo code cannot be compiled. It cannot be executed and there are no real formatting or syntax rules for writing pseudo codes.

It is simply an important step in producing the final code. Some important terms used in pseudo code for different activities are:

·         Input: Read, Obtain, Get and Prompt

·         Output: Print, Display, and Show

·         Computer: Computer, Calculate, and Determine

·         Initialize: Set and Initialize

·         Add one: Increment

The two major constructions in pseudo code structures are: Sequence and Selection (decision). Sequence indicates the continuous flow of the program, whereas selection uses logical comparison or conditional check for making decisions.

Example:

…………… IF (condition> THEN List of Actions ELSE List of Different Actions END IF ……………… …………………

Example:

READ A, B, AND C IF A is greater than C THEN DISPLAY A ELSE DISPLAY C END IF ELSE IF B is greater than C THEN DISPLAY B ELSE DISPLAY C END IF END IF STOP

Example:

INITIALIZE Count to zero DO WHILE Count is greater than or equal to 10 ADD 1 to Count PRINT Count ENDDO STOP

Advantages of Pseudo code:

1.     Since, it is language independent, it can be used by most programmers.

2.     It helps to design in plain natural language.

3.     It is easier to develop the program from pseudo code than with a flowchart.

4.     It is easy to translate to the programming language.

5.     Its simple structure and readability makes it easier to modify as well.

Disadvantages of Pseudo code:

1.     It does not provide the visual representation of the program logic.

2.     There are no accepted standards for writing pseudo code.

Algorithm

An algorithm is defined as a finite sequence of explicit instructions that produces an output with the set of input values. The steps in the algorithm are never ambiguous. It terminates after a finite number of steps.Algorithms can have repetitions and logical decisions until a specific task is completed. Algorithms are not computer programs. They cannot be executed by the computer.

Properties of Algorithm

An algorithm must have the following properties.

1.     There should not be any ambiguity in instructions.

2.     The instructions should be specific to the task.

3.     The description of an algorithm must be finite. It cannot be open-ended.

4.     The algorithm must be general enough for writing programs.

5.     As far as practicable, program codes should not be included in algorithms.

Example: Write an algorithm to make a telephone call.

Step 1: Remember or read the telephone number. Step 2: Lift the receiver Step 3: Is there a dial tone? If yes, then dial telephone, go to step 4. { If no, then put down the receiver. Go to step 2} Step 4: Speak Step 5: Put down the receiver.

Example: Write an algorithm to find the largest number among three input numbers.

Step 1: Start Step 2: Read 3 numbers say: A, B, C Step 3: Find the largest number between A and B and store it in MAXAB Step 4: Find the largest number between MAXAB and C and store it in MAX Step 5: Display MAX Step 6: Stop

Write the algorithm to calculate the interest on principle amount in N number of Years.

Step 1: Start Step 2: Read principle, Rate and Time Step 3: Multiply principle * Rate * Time Step 4: Divide by 100 Step 5: Write the answer Step 6: Any more calculations? { If yes, then go to step 2 If No } Step 7: Stop

Write algorithm to calculate the total and average marks of 10 students for 7 subjects.

Step 1: Start Step 2: Subject = 1 Step 3: Input mark for this Subject Step 4: Add marks and store into a variable Step 5: Are all subjects (7 subjects) done? { If No, then increase the subject number and go to step 3. If yes, then go to step 6 Step 6: Print the sum Step 7: Find average (divide by 7) Step 8: Print the sum and average Step 9: Are all (10 students done)? { If No, then increase the student number and go to step 2 If yes, then go to step 9} Step 9: End

 

 

Flowchart

INTRODUCTION

A flowchart is a diagram showing a sequence of events that describes the activities necessary to the solution to a problem. It is drawn using a set of conventional symbols. The symbols are connected by the arrowhead that indicates the order in which activities will occur. The different types of symbols that are used in flowchart are:

Features of Flowchart

Flowcharts have some basic features. The basic of a flowchart is its origination from where it begins.

·         Origination: Flowchart starts from the source of the collection of data. The data are the information to the computer. The original documents or manuscripts are the source documents that are the sources of information. The data goes to the second step.

·         Input: The data information is given to the computer so that the computer understands. The input section of the flowchart shows a process of getting data and instruction through a suitable device.

·         Processing: The data is processed by the computer for which instructions are necessary. The processed results are stored or used in further calculations. The processing symbols contain the information about the processing mechanism.

·         Output: The output of the processing may go for further processing cycle or the next step while data are processed in the computer.

·         Storage: The data is stored in the disks. The data and information are stored in the computer’s memory for further reference.

Types of Flowchart

The major two types of flowcharts are:

1.     System flowchart and

2.     Program flowchart

1. System Flowchart

System flowcharts give the direction of a program so that programs or modules are controlled. They display all the codes to be used in the main program and different modules. Such flowcharts give detail information to the programmer. This is like a processing machine. For example, information processing cycle, manufacturing industry, etc.

The above structure is a master block diagram of system flowchart. Each and every item is sub-divided into different modules and every module consists of numerous programs.

2. Program Flowchart

A flowchart which is used to process or solve a problem through a program is called program flowchart. The natures of problem differ from time to time. Use of different signs and symbols for developing different programs represent program flowchart. So, the size of a program determines flowchart.

Advantages of Flowchart

1.     They are clear graphical representations of the various paths that must be followed to perform the acts to accomplish the goal of the program.

2.     They provide help to make later modifications.

3.     It is very convenient to write algorithm and flowchart followed by the program codes instead of writing the programs directly.

4.     The advancement result of the algorithm is flowchart.

5.     Flowcharts enable to read the program very easily.

6.     With the help of flowchart, programs can be written in any language.

Disadvantages of Flowchart

1.     Flowcharts are new to the beginning programmer.

2.     It is a time-consuming task for the programmer.

3.     It is a tedious task to make modifications in flowchart after completing the program when required.

4.     Sometimes, the flowcharts are not clear to another programmer except the one who had designed it.

Flowchart Structures

Flowcharts can be very simple where few symbols can depict the logic. They can be complex too. There are three constructs of a flowchart. They are:

1.     Sequence:where the information can flow in straight line

2.     Selection:where the decision is made according to some predefined condition.

3.     Repetition:where the logic can repeat in a loop, i.e., where a sequence of steps is repeated until the desired output is obtained.

Flowchart Examples

1.     Write an algorithm and flowchart to make a telephone call.

Algorithm

Step 1: Remember or read the telephone number. Step 2: Lift the receiver Step 3: Is there a dial tone? If yes, then dial telephone, go to step 4. { If no, then put down the receiver. Go to step 2} Step 4: Speak Step 5: Put down the receiver.

Flowchart

2.   Algorithm and flowchart to calculate the interest of principal amount in N number of years.

Algorithm

Step 1: Start Step 2: Read principle, Rate and Time Step 3: Multiply principal * Rate * Time Step 4: Divide by 100 Step 5: Write the answer Step 6: Any more calculations? { If yes, then go to step 2 If No } Step 7: Stop

Flowchart

3.  Write an algorithm, flowchart and program to find the total and average marks of 10 students for 7 subjects and print the result.

Algorithm

Step 1: Start Step 2: Subject = 1 Step 3: Input mark for this Subject Step 4: Add marks and store into a variable Step 5: Are all subjects (7 subjects) done? { If No, then increase the subject number and go to step 3. If yes, then go to step 6 Step 6: Print the sum Step 7: Find average (divide by 7) Step 8: Print the sum and average Step 9: Are all (10 students done)? { If No, then increase the student number and go to step 2 If yes, then go to step 9} Step 9: End

Flowchart

Program Structures

A program is initiated with a declaration of data types, definition of function procedures, subprograms or sub-procedures. As soon as the program is initiated, the data types are declared in the program. After the data are defined, the data are processed in different order. The order at which the program codes are written can be classified in the following categories.

1.     Sequence

2.     Control Structures

3.     Selection

4.     Repetition

Sequence: When a program is written in linear fashion, the program is in a sequence. The program initiates at a certain level and continues till the last command or statement. Such fashion is useful when the program is small and less logical.

Control structures: The program which contains certain logic, jumps from one point to another and certain repetition possesses control structures. The control structures mostly used are:

1.     use of goto ... statement

2.     use of on … goto … statement

3.     user of if … then, if … then … else statement

4.     use of embedded if …else if … else if … else … end if statement.

Selections: A selection is choosing options. The program provides different options. The user can choose an option as required. The common statements used for this activity are:

1.     Select

2.     Case

3.     Switch

These statements provide choices for menu driven programs. Although the syntax and users in the different programming language are similar, we cannot rule out the variation. Therefore, the reader will have to consult the necessary manual referred to the particular programming language for the complete idea of these selections.

Repetitions (Loops): When a program goes through a loop for certain times repeatedly, it is known as repetition. There are two types of loops. They are; finite loop and infinite loop. The infinite loop stops after executing certain program codes or repetitions.

An infinite loop never ends. The loops are constructs of programs. The first value that initiates program loop is called initial value and the last value reached in a finite loop is known as a sentinel value. When the sentinel value is obtained, the program stops looping. The different methods of creating loops are:

1.     Do loop

2.     While loop

3.     For loop

 

·        Context Diagram

In keeping with the top-down approach to requirement determination, the first graphic that is produced using structured technique is the context diagram. It gives a broad overview of the information system environment including the data flows into and out of the system.

Context Diagrams serve three important purposes

1.     Context diagrams support a data-oriented approach to system design.

2.     Context diagrams help to investigate the output and process requirements of the organization.

3.     Context diagrams defines the boundaries of the proposed system.

Levels of Context Diagram

There are three levels of context diagrams:

1.     Level 1: A user-level diagram describes one functional area’s operational activity.

2.     Level 2: A combined user-level diagram provides an overall view of the activities of related user groups.

3.     Level 3: An organizational level diagram reflects a consolidated view of the activities of the organization.

Context diagram for order processing

Problem Narrative

The customer sends a list of items required, which is processed by the customer handling department. A copy of the list is sent to the stores. Based on the item price, an estimated value of goods is prepared and sent to the client. At the end of the month, consolidated list of the customer requests are prepared and sent to the manager of the sales department.

Draw the context diagram based on above narrative.

·        Data Flow Diagram

A Data Flow Diagram (DFD) is a pictorial representation of the path which data takes from its initial interaction with the system until it completes any interaction. The diagram will describe the logical data flows without detailing the movements of any physical items.

The DFD also gives insight into the data that is used in the system. It does not show a sequence of steps. It shows only what the different processes in a system are and what data flows between them. Preparing context diagram is a preliminary step in creating a data flow diagram (DFD).

Based on context diagram, data flow diagrams identify the major data flows within the system boundaries, the process and the data storage.

Levels of Data Flow Diagram

The complexity of business system means that it is impossible to represent the operations of any system by means of single data flow diagram. At the top level, an overview of the different systems in any organization is shown by way of context analysis diagram. When exploded into DFD, they are represented by:

Level 0: System Input and output

Level 1: Subsystem level data flow – Functional Level

Level 2: File level detail data flow

The input and output data were shown should be consistent from one level to the next.

Level 0: System Input/output: A level-0 DFD describes the system-wide boundaries detailing inputs to and outputs from the system and major processes. This diagram is similar to the combined user-level context diagram.

Level 1: Subsystem level data flow: A level-1 DFD describes the next level of detail within the system detailing the data flows between subsystems, which make up the whole.

Level 2: File level detail data flow: A level-2 DFD details the files to which the data is applied in the system and from which data is obtained. Each individual process is shown in detail.

Order Tracking System

Level 0

Level 1

Level 2

Entity Relationship Diagrams (E-R Diagram)

Entity Relationship Diagrams (ERD) are graphic illustration used to display object or events within a system and their relationships to one another. E-R diagrams model data is much the same way as DFD's model processes and data flows.

Purpose of ER Diagram

1.     Verify accuracy and thoroughness of data design, current and new, with users.

2.     Organize and record organizational data entities, relationships and scope through decomposition and layering.

3.     Enhance the overall communication between development project team member’s system technicians, management and users with the use of graphic models.

4.     Generally, simplify and bolster the creative data design process.

·        Decision Tree

Decision Tree provide a graphic representation of decision logic that helps non-computer people easy to understand. The principles for the development of decision tree are relatively forward.

1.     Identify all conditions

2.     Find out values these conditions may take or assume

3.     List all possible outcomes

Decision Tree are graphical representations of the decision table. These are also available and aid the construction of decision tables.

A decision tree helps to show the paths that are possible in a decision following an action or decision by the user. A decision tree helps prefer the easier-to-follow mapping of a complex design. This mapping should show branch point forks, but not the details of the user dialogue.

Example:Decision trees help designer visualize how the user will move through the design to reach the desired location.

Decision Tables

Using decision tables, decision trees conditions and outcomes are listed in the form of two-dimensional tables. A decision table, as compared to a decision tree, checks all the possible combinations that might arise for all conditions.

General Format of Decision Tables

List of conditions	Columns representing logical combinations of conditional value
Lit of outcomes	Resulting outcome for each set of conditions

Decision table is a tabular method for describing the logic of the decisions to be taken. Decision table accompanies the flowcharts defining the possible contingencies that may be considered with the program and appropriate course of action for each contingency.

Decision tables can be divided into four parts:

1….Condition-Stub:
It consists of a list of all the conditions that are to be taken account of. Condition entries that complete the condition statements. They are tabular representation of the combination of the conditions that are to be satisfied, for each of particular action, that is given a “Y” of “N” or ___x____’ mark is placed to indicate whether a particular condition is to be considered or ignored.

2….Action-Stub:
It consists of all the possible actions that are to be taken.

3……Action-Entries:
Action entries are entries that complete the action statements.

4……Data-Dictionaries:
Data dictionary defines each term called data element, encountered during the analysis and design of the new system. Data elements can describe files, data flows or processes. For example, you want to print the vendor’s name and address at the bottom of the cheque. The dictionary might define vendor’s name and address as flows:

Vendor_name +

Street +

City +

State +

Phone +

Fax +

Email

This identification becomes a part of the data dictionary that ultimately will list all key terms used to describe various data flows and files.

Major Symbols:

The symbols used white preparing data dictionaries are:

= equivalent to

+ and

[] either/or

() optional entry

.