system development life cycle

System development life cycle objectives of study:

System development life cycle objectives of study Explaining the various stages of SDLC Understanding the concept of system investigation Describing system analysis Explaing the methods of system design Explaining system testing, system implemtation and system maintaineances.

System analysts:

System analysts SDLC is a set of activities carried out by the system analysts and developers to develop an information system System analyst is responsible for designing or modifying the existing information system to improve the efficiency in functioning of an organization. System analyst deal with all aspects of an organization and its operations such as planning, monitoring, testing, accounting, forecasting, coordination, scheduling.

Following questions are considered in order to apply the steps of SDLC in the new information system:

Following questions are considered in order to apply the steps of SDLC in the new information system Do we have support from management ? Is this an appropriate time for project commitment ? Does the information systems help the organization to achieve its goal / Do we have adequate resources and expertise for the implementation of the information system ? Is the development of information system worthwhile ?

System Investigation:

System Investigation Defining the problem: The system analyst identifies the problem and prepares a written statement of objectives and scope of the new system. The problem in a system may occur due to following reasons: If the existing system is not working properly If the existing system is unable to handle the workload. If the existing system is not cost-effective. If the system is not accurate and reliable. If the system is not secure.

Feasibility studies:

Feasibility studies Feasibility Study: It is to assess alternative systems so that most feasible system for the system development process can be designed. Consider the following questions to perform feasibility study. Does the present system meet the required business needs ? What are the risks involved in the present system ? Does the expanding business will allow it to cope with extra workload or not.

Following are the main categories to assess the feasibility of proposed system:

Following are the main categories to assess the feasibility of proposed system Organizational Feasibility is to determine whether the system can be implemented successfully in an organization or the system is not effecting the working of an organization in a negative way. It also determines if the proposed system meets the organizational goals or not. Economic Feasibility deals with the cost that can incur while implementing the system. The questions raised by the system analyst in the system investigation such as: 1.The cost of conducting a full system investigation. 2. The cost of hardware and software required for implementing the new system application. 3. The benefits of the new system such as reduced costs, improved customer service and improved utilization of resources.

Technical Feasibility:

Technical Feasibility It examines whether the proposed system is technically suitable with the available hardware, software and other technical resources. It also involves whether or not the end users have enough experience of using that technology. The following questions considered for developing the system: 1. Is the proposed technology capable of managing the data required by the new system ? 2. Does the proposed system provides adequate responses regardless of number of users using the system / 3. Is the proposed system flexible enough to be expanded in the organization ? 4. Does the proposed system provide security, accuracy, reliability and accessibility ?

Operational Feasibility:

Operational Feasibility It is based on the ability of the management, customers and suppliers to operate, use and support a proposed system. The following questions are considered for evaluating operational feasibility. Is there sufficient support from the management, employees, customers and suppliers for the implementation of new system? Is current system compatible for the new business strategy and acceptable to the users ? Whether or not the users are involved in planning and development of the new system ?

Legal feasibility & Scheduled feasibility:

Legal feasibility & Scheduled feasibility Legal feasibility verifies whether or not the system abides all the laws and regulations of the organization and all the software policies. Scheduled feasibility evaluates whether the system is able to complete its tasks within the given time of development or not. The following questions can be arised : 1. Is the system being developed as per the business rules, regulations, laws and union agreements ? Is the system legally feasible ? Is the system schedule feasible ? Are the end users actively participating in the development of information system ?

2.System Analysis: Objectives::

2.System Analysis: Objectives: To Know how a system currently operates. To identify the user’s requirment in the proposed system. Requirements of a system can be determined by tools like: Information Gathering tools * Interview * Questionnaire * Record Review * Observation

QUESTIONNAIRE: :

QUESTIONNAIRE: Acquiring information of the questions before conducting the interview. Gaining information regarding the questions in order to prove facts found in the interview. Acquiring information on: 1. What users feel about the current system ? Is there any problem remaining unsolved ? What do people expect from a new or modified system ?

INTERVIEW:

INTERVIEW It is the method of collecting information in which there is a face to face conversation with people of the concerned department . It can be of two types formal or informal and the questions can be of two types structured or unstructured. The analyst must plan the interview and must know the following issues in advance. 1. Whom to interview ? 2. When to interview ? 3. What to ask ? Where to hold the interview ? How to begin the interview ? How to conclude the interview ?

RECORD REVIEW:

RECORD REVIEW It refers to review of the documentation of information system to establish quantative information regarding volumes, frequencies, trends and ratios. Documentation of information system includes written policy manuals, regulations and standard operating procedures used by the organization as a guide for managers and other employees.

OBSERVATION::

OBSERVATION: It allows analyst to gather information which they cannot obtain by any other fact-finding methods. They can get first hand information through observation whereas by reviewing the documents, they get secondary information. Nowadays electronic observation and monitoring methods are used as information gathering tools because of their speed and efficiency.

b. Structured Analysis Tools:

b. Structured Analysis Tools DATA FLOW DIAGRAM DATA DICTIONARY DECISION TREES STRUCTURED ENGLISH DECISION TABLES

DATA FLOW DIAGRAM :

DATA FLOW DIAGRAM It is the graphical representation of the logical flow of data in a system. It is used to represent input and output of data in a system and is represented by arrows. There are two types of DFD’s 1 . Physical DFD : It provides details about the hardware, software, applications and people involved in the implementation of the system. 2. Logical DFD : It is the implementation of independent view of a system that focuses only on the flow of data between processes or activities.

RULES TO CONSTRUCT DFD:

RULES TO CONSTRUCT DFD Each process involved in system should be named and numbered or easy reference. Name of each process should be symbolic. The flow of information in DFD should be from top to bottom and from left to right. When a process is divided into several lower level processes, each low-level should be numbered. The names of the data stores, sources and destination should be in the upper case.

DATA DICTIONARY:

DATA DICTIONARY It serves as a common database for programmers and used in controlling all tasks of the system. There are four main components. 1. Data element : It is a field which cannot be further classified. For ex in an Inventory system an Invoice Number and Amount Due are data elements which cannot be classified further. 2. Data structure : It is a group of data elements as its fields. For ex Customer Data have First name, Middle name, Last name, address and State. 3. Data flow 4. Data Store

DECISION TREE:

DECISION TREE It is the method for defining complex relationships between the branches of a system. In a decision tree, a square node indicates an action and circle node indicates a condition. At each step of software development, all possible alternatives of a decision tree are determined. This process continues until the main objective of developing the decision tree is not obtained.

Structured English:

Structured English In this decisions are made using If, Then, Else, Repeat, Until ad Do statements. It is intended to reflect the logical hierarchy of a program. While using structured English following rules should be: Express all logic in terms of sequential structures, decision structures. Use keywords such as If, Then, Else, Do, Do-While etc. Underline the words or phrases defined in a data dictionary in order to signify that they have a special meaning.

Decision Table:

Decision Table It is a matrix containing rows and columns that are used to define relationships between the data elements of rows and columns that are used to define relationships between the data elements of a program. It consists of two parts, stub and entry. The stub is further divided into upper quadrant and lower quadrant. The upper quadrant known as condition stub and lower quadrant known as action stub. The entry also subdivided into upper quadrant as condition entry and lower quadrant as action entry.