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System

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System

System (from Greek Word systma,)is an organized relationship amongfunctioning units or components.

System is an orderly grouping ofinterdependent components linkedtogether according to a plan toachieve a specific objective.

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Characteristics Of Systems

Organization: Implies the Structure and order. It is thearrangement of components to achieve objectives

Interaction: Refers to the manner in which eachcomponent functions with other components of thesystem. (Ex computer)

Interdependence : Means that parts of the organizationdepends on one another.

Integration : It is concerned with how a system is tiedtogether.

Central Objective : Each system works to achieve acommon objective

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Elements Of a System

Inputs :- material or information thatenters a system

Outputs : - Outcome of Processing

Process : - Involves actualtransformation of input into output

Contd

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Elements Of a System contd

Control :- It is a decision makingsubsystem that controls the pattern ofactivities governing input, process and

output (Ex OS)

Feedback :- Control in dynamic system isachieved by feedback. It may be positive

(reinforce performance) or negative (needaction)

Contd

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Elements Of a System contd

Environment : - Is thesuprasystem within which anorganization operates.

Boundaries :- Limits that identify itscomponents , processing and its

interrelationship (Ex ATM onlyWithdraw)

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Types Of System

Physical or abstract systems

Open or closed systems

Man made systems

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Physical System : - Are tangiblesystems . Ex : - computer system

Abstract System :- are conceptual ornonphysical entities . Ex: Model ,Formula

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Open System :- Interacts with itsenvironment

Closed System :- Do not Interactwith its environment . Is isolatedfrom environmental influences

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ManMade Information System : - Aninformation system (IS) is typically considered to bea set of interrelated elements or components thatcollect (input), manipulate (processes), anddisseminate (output) data and information andprovide a feedback mechanism to meet anobjective.

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Major Information Systems are :-

Formal Information System

Informal Information System

Computer Based Information System

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Formal Information System : - Is Basedon the organization represented by theorganization chart. It is concerned with the

pattern of authority and Communication

Informal Information System :- It is anemployee based system designed to meet

personnel needs and to solve work relatedproblems

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Computer-based Information System : - AnInformation System is an organized combination ofpeople, hardware, software, communication networks andthe data resources that collects, transforms and

disseminates information in a organization.

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INFORMATION

TECHNOLOGY

Hardware

Software

Databases

Networks

Other related

components

are used to build

INFORMATIONSYSTEMS

Payroll

System

Inventory

System

Marketing

System

Customer

Service

System

IS Vs IT

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Systems Development LifeCycle (SDLC)

SDLC is the process of creating or altering systems,and the models and methodologies that people use todevelop these systems.

System life cycle is an organizational process ofdeveloping and maintaining systems.

It helps in establishing a system project plan, becauseit gives overall list of processes and sub-processes

required for developing a system.

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Steps of SDLC (Waterfall Model)Need

Recognition

Feasibility

Study

Requirement

Analysis

System

Design

Coding &Testing

Implemen-

-tation

Maintenance

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Need Recognition

What is the problem ?

One must know the problem before it issolved.

It leads to preliminary survey or

initial Investigation to determinewhether an alternative system cansolve the problem.

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Feasibility Study

Depending on the results of the initialInvestigation , the survey is expanded toa more detailed feasibility Study

It is a user oriented overview of theproposed information systems purpose

and feasibility.

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Types Of Feasibility

Economic Feasibility : - Involves questions suchas whether the firm can afford to build theinformation system , whether benefits exceedscosts.

Technical Feasibility :- - Involves questions suchas whether the technology needed for theinformation system exists & whether the firm has

enough experience using that technology

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Organizational Feasibility : - Involvesquestions such as whether the informationsystem has enough support to beimplemented successfully

If the IS appears to be feasible , this phase

produces a functional specification(Formal Proposal)

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Formal Proposal consists of :-

Statement of the problem

Summary of findings & recommendations

Details of findings

Recommendations & conclusions

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Analysis

Analysis is a detailed study of the variousoperations performed by the system and theirrelationships within and outside the system

It is a process of collecting factual data,understand the processes involved, identifyingproblems and recommending feasiblesuggestions for improving the systemfunctioning.

It determines whether or not a candidatesystem should consider other related systems?

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This involves studying the business processes,gathering operational data, understand theinformation flow, finding out bottlenecks andevolving solutions for overcoming the weaknesses

of the system so as to achieve the organizationalgoals.

System Analysis also includes subdividing of

complex process involving the entire system,identification of data store and manual processes.

DFD , Interview & Questionnaire are tools used in

analysis

Analysis Contd..

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System Design

Based on the user requirements and the detailedanalysis of the existing system, the new systemmust be designed.

System designing is the most crucial phase in thedevelopments of a system.

The design process translates requirements into arepresentation of the software that can be assessedfor quality before coding begins.

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Design

Design focuses on four distinctattributes of a program:

Data structure Database(Fields / types) Software architecture (Function Hierarchy)

Interface representations(Forms ,reports, Screens)

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Coding

The design must be translated into a machine-readable form.

The system design needs to be implemented tomake it a workable system.

This demands the coding of design into computerunderstandable language, i.e., programminglanguage.

This is also called the programming phase

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Testing

The testing process focuses on thelogical internals of the softwareensuring that all statements have been

tested

Conduct tests to uncover errors and

ensure that defined input will produceactual results that agree with requiredresults.

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Testing

Unit Testing :- Test Each Program separately

System testing:- Test the functioning of the system asa whole. Ex:- Performance Test , Stress Test

Acceptance Testing :- User Acceptance Testing(UAT) is a process to obtain confirmation by the clientthat the modification or addition meets mutuallyagreed-upon requirements. It is one of the final stages

of a project and often occurs before a client or customeraccepts the new system. Types : Alpha Test(developer site) & Beta Test (Customer Site)

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Implementation

Is the process of putting the systeminto operation in an organization.

It includes training and conversion

Training : - Is the process of

Ensuring that system participantsknow what they need to know aboutsystem

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Conversion : - Different types ofconversions are : -

Direct

Pilot

Parallel

Phased

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Direct Conversion :- involves animmediate conversion to the new system.

This method can appear cheaper but is full ofproblems.

If the new system is not working right it maymean loss of data which may have hugeimplications depending on the type of data.

It is not recommended

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Parallel Conversion: Involves the old andnew system working side by side.

Some operations are gradually implementedinto the new system while the old system isstill running.

After all the operations have been carried out

under the new system and the new system hasbeen debugged then the old system isdiscontinued.

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Phased Conversion: This involves thegradual implementation of the new system.

As the various operations are tried on thenew system , the old is discontinued inthose operations

Ex : If the system is introduced by

functions , a new payroll system mightbegin with hourly workers , then addsalaried Employees

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Pilot Conversion: Involves implementingthe new system in only a small part of theorganization such as single department .

If there are any problems with the newsystem then the old system is still there asa backup.

When it starts working smoothly it isinstalled in he rest of the organization

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Maintenance

Both users and technical specialistsdetermines how well it has met its objectivesand decide whether any revision is requiredor not .

Software will undoubtedly undergo changeafter it is delivered to the customer

software must be adapted to accommodatechanges in its external environment orbecause the customer requires functional orperformance enhancements.

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Strengths of SDLC

Oldest and Most Widely Used

Simple

Step-by-step process

Ensures consistency on sequence ofphases and how they are followed.

Distinct milestones and deliverablesfor each phase

Supports project management

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Weakness of SDLC

Inflexible because real projects rarely followthe sequential flow that the model proposes

It is often difficult for the customers to state all

requirements explicitly.

The customer must have patience to wait tovalidate the software product in the latephases. (until programs are implemented)

Difficult to respond to changing customerrequirements

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The Prototyping Model

Often, a customer defines a set of general objectivesfor software but does not identify detailed input,processing, or output requirements.

In other cases, the developer may be unsure of theefficiency of an algorithm, the adaptability of anoperating system, or the form that human/machineinteraction should take.

In these, and many other situations, aprototypingapproachmay offer the best solution.

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Prototype

L isten tocustomer

Customer

test-drives

Prototype

Build/revise

Prototype

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Types of prototyping

Throwaway prototyping :- Also called close ended prototyping orRapid Prototyping .

Throwaway refers to the creation of a model that will eventually bediscarded rather than becoming part of the final delivered software.

After preliminary requirements gathering is accomplished, a simpleworking model of the system is constructed to visually show the userswhat their requirements may look like when they are implemented intoa finished system.

The method used in building it is usually quite informal, the most

important factor being the speed with which the model is provided.

The most obvious reason for using Throwaway Prototyping is that it canbe done quickly

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Evolutionary prototyping :- builds a very robustprototype in a structured manner and is constantly refined .

The Evolutionary prototype, when built, forms the heart ofthe new system, and the improvements and further

requirements will be built.

When developing a system using Evolutionary Prototyping,the system is continually refined and rebuilt.

Evolutionary Prototypes have an advantage over ThrowawayPrototypes in that they are functional systems. Althoughthey may not have all the features the users have planned,they may be used until the final system is delivered.

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Incremental prototyping :- Thefinal product is built as separateprototypes. At the end the separate

prototypes are merged in an overalldesign.

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Good to deal with the following cases:

Customer can not provide the detailedrequirements

Very complicated system-user interactions

Use new technologies, hardware andalgorithm

Develop new domain application systems

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Drawbacks

Insufficient analysis: The focus on alimited prototype can distract developersfrom properly analyzing the complete project.

User confusion of prototype and finishedsystem: Users can begin to think that aprototype, intended to be thrown away, is

actually a final system that merely needs tobe finished or polished

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Developer attachment to prototype:Developers can also become attached toprototypes they have spent a great deal ofeffort producing it.

Excessive development time of theprototype: A key property to prototyping isthe fact that it is supposed to be done quickly.

If the developers lose sight of this fact, theyvery well may try to develop a prototype thatis too complex. When the prototype is thrownaway the time spent is wasted