SDC

 

CHAPTER 1

SYSTEM DEVELOPMENT CONCEPT

1. System : 

A system is a set of components that work together to perform a specific task. It accepts input then processes it and gives the required output.

 

 

2.            Information system :

Information system is a system which collects data and processes it to generate meaningful information. The major components of an information system are input, people, process, hardware, software, data and output.

 

Components of Information system:

1. Hardware: hardware refers to the physical layer of the information system. It includes computers, networks, scanners, digital capture devices, and other technology-based infrastructure.

 

2.            Software: software refers to the logical layer of information system that makes hardware function properly. It includes system software (OS, device driver, etc.) and application software.

 

3.            Data: data is raw facts, figures, and measurements, etc. which are used as input for the system. It may be alphabets, digits, figures and other symbols.

 

4.            Processes: processes, or procedures, describe the tasks that users, managers, and IT staff members perform.

 

5.            People: people refer to users who interact with information systems. The users within the organization include managers, technicians, sales representatives, corporate officers, etc. are called internal users and the users outside the organization include customers, suppliers, etc. are called external users.

 

2.1 Types of information system :

 

a.            Transaction Processing System(TPS)

b.             Management Information system (MIS)

c.             Decision Support System (DSS)

d.            Executive Information System (EIS)

a.            Transaction Processing System(TPS)

It is a type of operational level (low level) system. It is a computerised system that records the daily routine transactions necessary to conduct business.

 

2.  Management Information system (MIS)

It assists middle level management. It makes the use of the already processed transaction data, which is obtained from the TPS and generates information reports after processing data. 

 

3. Decision Support System (DSS)

It provides interactive support for the decision-making processes managers and other business professionals.

 

4. Executive Information System (EIS)

It provides critical information from many sources customized to the information needs of executives.

 

3. System Analyst :

            System analyst is a person who analyses systems and designs the system according to the requirement.

 

3.1. Characteristics of System Analyst

1. System analysts must have good knowledge of organization.
2. System analysts must have knowledge of computer systems.
3. System analysts must be good listeners with friendly behaviour.
4. System analysts must be able to present his communication skills.
5. System analysts must be able to find solutions to problems.
6. System analysts must have breadth of knowledge.

 

3.2 Roles of System Analyst

1. Change Agent :

            System analyst should change himself as per the requirement.

2.            Investigator and Monitor :

System analyst should  investigate and monitor to run the system

3.            Architect

            System analysts should create physical and logical design of a system.

4.            Psychologist :

            System analysts should read the minds of users and co-workers.

5.            Motivator : 

System analysts should motivate people.

6.            Defining and prioritizing the requirements.

System analysts should  define a requirement and manage them as per requirements.

7.            Analysis and evaluation

            System analysts should analyze and evaluate the user’s comment.

8.            Designing system

System analysts should design the system that can be easily understandable and flexible.  

4. System Development Life Cycle (SDLC)

            The process of developing a system by a set of predefined steps is called system development life cycle.

 

4.1 Importance and necessity of SDLC

The designing of system using SDLC is necessary due to following reasons:

1. The size of organizations is becoming larger.

2. Computer based processing enables the same data to be processed in many ways 
                based on needs.

3. Information and time is now of great importance.

4. Organizations having many branches.

5. Systematic distribution of organization.

 

4.2 SDLC Phase  (SADDTIM)

1. System Study ;

            System study studies the following  questions: 

`                       what is to be done in the future ?

                        How to do it ?

                        When to do it ?

                        Who is to do it ?

 

Feasibility study :

            The term ‘Feasibility’ means possibility to do something. In the development of software also, feasibility study is most because we cannot develop the software which is not possible for the human beings and which is not possible due to the technology and other many factors. So, before developing the software, the feasibility study should be completed. In this phase, usually the following factors should be considered:.

Types of feasibility study :

1.    Economic Feasibility: It determines the total cost of development, running or operation cost in the future and the profit percent of the organization with the project.

2.    Operational Feasibility : It is all about the problems that may occur during operation of the system after its development.

3.    Technical Feasibility : It is the study that the technical requirements of the developing system are available or not in the market.

4.    Behavior Feasibility : It concerns with the behavior of the users and the society towards the new system.

5.    Time Feasibility : It determines, whether the developing system can be completed or not within the deadline of time.

6.    Legal Feasibility : It concerns legal issues of the system. If the system is illegal, then the system designing is meaningless.

 

2.            System Analysis :

            It  is the detailed study of the various operations performed by the system. Like finding problems.

 

3.            System Design :

It is concerned with the final logical design of the complete system.

Tools :

·         Algorithm/Flowchart

·         Pseudo code / context diagram

·         Data Flow Diagram (DFD)

·         Entity Relationship diagram (ERD)

 

            Types of system design

            1. Top Down Approach

            2. Buttom-up Approach

 

Top-down approach : The complex module is divided into submodules. 

Bottom-up approach: Begin with small modules and then combine them in one.

 

4.            System development :

The process of converting design into a program is called system development.

In order to develop a system we need programming language like C, C++, JAVA, PYTHON, FORTRAN etc.

 

5.            System Testing :

The process of reducing bugs/errors from the system is called system testing.

Methods of system testing :

1.    White Box Testing

2.    Black Box Testing

 

5. System Implementation:

The way of carrying out a developed system into working condition is called system implementation.

 

6. System maintenance and review:

Correcting and upgrading the process of the system is called system maintenance.

Review means viewing the system meets its objectives or not. 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

5. System Development Model

5.1 The waterfall Model

What is Waterfall Model? Describe with a figure.

 

This is the oldest model of the system development. As the water flows from top to the downwards and never turns back until the force is applied, the system development process in this model also never turns back, after it is proceed.

 

 

 

 

The advantage of this model is that it is very easy to understand, as it follows the sequential linear similar to waterfall.

But the disadvantage of this model is that it does not allow to return back to the step once it is proceed, until the completion of all the development stages. The following figure illustrates this model:.

 

The different stage of waterfall model are given below:

i. Requirement Analysis and Definition

This is the first stage of the Waterfall model where the developer should identify the actual requirements of the given problem. When the problem is analyzed then the programmer should follow the next stage.

ii. System Design

In this stage of software development, developers are involved in identifying and describing the fundamentals of software system abstractions and their relationships. It establishes overall system architecture.

iii. Implementation and Unit Testing

In this stage, after designing the system, the set of programs or program unit involves verifying that each unit meets its specification or not. After unit testing, the system will be implemented.

iv. Integration and System Testing

The developed system is tested in order to ensure that the newly developed system is working properly or not. After testing, the software system is delivered to the customer.

v. Operation and Maintenance

The maintenance involves in correction of errors which were not discovered in earlier stages of the life cycle, improving the implementation of system units and enhancing the system service as new requirements are discovered. The hardware and software requires periodic maintenance so that the system works in proper condition.

 

Advantages :

1.     It is a simple model suitable for small size projects.

2.     It is less expensive.

Disadvantages :

1.     It is not suitable for large size projects.

2.     High amounts of risk and uncertainty. 

5.2 Prototyping Model

It is the repeating process of system development which is more appropriate for developing a new system where there is no clear idea of requirements, inputs and outputs. In this model, a prototype or a sample of the developing model is developed and reviewed. Gradually, the requirements are fulfilled in other stages. It is a repeating and trial process until the completion of a final software.

1. Identify the user needs: the system analyst interviews the user to obtain an idea of what is required from the system.
2. Develop a prototype: the system analyst, working uses one or more prototyping tools to develop a prototype.
3. Determine if prototype is acceptable: the analyst educates the user in prototype use and provides an opportunity from becoming familiar with the system.
4. Use the prototype: the prototype becomes the operational system.

Advantages:

1. Strong Dialogue between users and developers
2. Environment to resolve unclear objectives

 

Disadvantages :

1. No completion deadline.
2. Approval process and requirement is not strict

 

5.3 Spiral Model :

This is also one of the popular model of software development. In this model, a software model is prepared, sent in the market for testing and upgrade as the different versions. This model has the combined features of Waterfall model and Prototype Model. It is known as spiral because, the development process proceeds from the center to the outside of the circle as the different versions. One complete circle means one complete version.

1. Planning : The project is reviewed and a decision made whether to continue or not.
2. Risk Analysis : detailed analysis is carried out to identify project risk.
3. Software Development : After risk evaluation, a development model for the system is chosen.
4. User evaluation : feedback of user evaluates the project whether it meets user needs or not.

 

 

 

 

 

 

 

 

 

 

6. Concept of system Design Tools:

6.9. Context diagram

It is a system design tool, which is used to show the detail overview of the system interactions with it’s external environment .It is very similar to the DFD but it does not use the storage symbol, so it is known as 0 level DFD (Data Flow Diagram), too. 

6.10. Data Flow Diagram

It is also a system design tool and more advanced than the context diagram. It is very similar to the context diagram but it displays the storage also. So, all the symbols used in context diagram are same but it uses one more symbols for storage, which is the open rectangle.

 

6.11. Entity Relationship Diagram (ERD)

The diagrammatic representation of entities attributes and their relationship is described by ER diagram. The basic components of ER diagram are :

Entity ; any thing or object.

Attribute : Properties of entity

Relationship ; association of entities.

Lines ; connector of entities

 

6.4. Algorithm

It is a step by step instruction to solve a problem. 

 

6.5. Flowchart

It is a pictorial form of an algorithm

 

6.6. Pseudo code

It is a more simple form of algorithm.

 

.6.7 Decision Table

It allows us to identify the exact course of actions for given conditions in tabular form.

 

6.8 Decision Tree

It allows us to identify the exact course of action for given conditions in tree structure.

 

6.9 CASE Tools

Computer Aided Software Engineering tool is an automatic computer based program.

 

6.10 Unified Modelling language (UML)

UML stands for Unified Modeling Language, which is a designing tool of software development. It has become very popular and it has been used by the popular and leading software companies like Microsoft, IBM, Oracle, etc. It is especially used for the OOP (Object Oriented Programming). It uses the simple graphical notations to express the design of software projects. The development of UML began in late 1994. 

6.11 Use Case 

A use case in software engineering is a description of steps or actions between a user and a software system which leads the user towards something useful.

 

Documentation :

Documentation consists of the detail description about software requirements specification, feasibility report, software designing report, description about input-output and processing mechanism, source code, comments, manuals, guides and effective help desk.

 

Why documentation needed ?

1. It is a means for transfer of knowledge of system.
2. To help requirements of the organization.
3. To migration to a new software.

 

Internal Documentation

It is used by the system analyst and the programmer during development process.

 

External Documentation

It is used by the user during the running time of the software.