system analysis and design_nidhi

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System Analysis and DesignQ-1 What is system? Briefly explain various types of system.Answer:"A system is an orderly grouping of interdependent components linked together according to

a plan toachieve a specific objective."The following three points come to the surface.i. System is a group of components.ii. The components are interdependent.iii. The components are linked together to achieve a specific objective.Types of Systems

(i) Physical or abstract systems(ii) Open or closed systems(iii) Deterministic or probabilistic systems(iv) Man-made information systemsPhysical or Abstract Systems

Physical systems are tangible entities that may be static or dynamic in operation. Forexample, thephysical parts of a computer center are the office, desk and chairs that facilitate theoperation of thecomputer. They can be seen or counted. They are static.Abstract systems are conceptual or non-physical entities. They may be as straightforward as formulae of relationship among sets of variables or models.Open or Closed Systems

A system interacts with its environment through the interfaces located on the boundary. Asystem issaid to be an open system, if there exists an interaction between the system and its

environment. Ifthere is no interaction of the system with its environment, the system is said to be a closedsystem.Deterministic or Probabilistic Systems

A deterministic system is one in which the occurrence of all events is perfectly predictable.Anexample of such a system is a numerically controlled machine tool.Probabilistic system is one in which the occurrence of events cannot be perfectlypredicted. An example of such a system is a warehouse and its contents.Man-made Information Systems

These systems are developed by man to process information to produce useful information.Most of the

computer based systems come under this category railway reservation system, payrollpackages, salesmonitoring software._ formal information systems_ informal information systems_ computer based information system.Computer based information system. system depends mainly on the computer for handlingbusinessapplications.They are classified as:

_ Transaction Processing Systems (TPS)_ Management Information Systems (MIS)

_ Decision Support Systems (DSS).


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_ Office Automation Systems (OAS).CBIS in an Organizations ContextHIERARCHICAL VIEW OF CBIS

Q-2 (a) What is SDLC? What are its stages?

Answer: SDLC stands for system development life cycle. The analyst must progress fromone stage toanother stage, answering key question & achieving results in each stage.STAGE KEY QUESTION RESULT

1. Recognition of needPreliminary survey/

initial investigationWhat is the problem oropportunity?Statement of scope andobjectives Performance criteria2. Feasibility study

_ Evaluation ofexisting system andprocedures_ Analysis ofalternativecandidate systems_ Cost estimatesWhat are the user'sdemonstrable needs?Is the problem worth solving?How can the problem beredefined?Technical/behavioral feasibilityCost/benefit analysis Systemscope and objectiveStatement of new scope andobjectives3. Analysis_ Detailed evaluationof present system_ Data collectionWhat must be done to solve theproblem?

What are the facts?Logical model of systemi.e.,data dictionary, data flowdiagram Pertinent data

4. Design_ General designspecifications_ Detailed designspecifications Output Input

Procedures_ Program


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construction_ Testing Unit testing Combined moduletesting User acceptancetestingIn general, how must theproblem be solved?Specifically, how must theproblem be solved?What is the system (processing)flow?Does the user approve thesystem?How well do individualprograms/modules test out?

How ready are programs foracceptance test?Design of alternative solutionsFinal Cost/benefit analysisHardware specificationsCost estimatesImplementation specificationsImplementation scheduleApproval of system by userProgramsTest plansSecurity, audit and operating

proceduresActual hardware useFormal System test5. Implementation_ User training_ File/systemconversionWhat is the actual operation?Are user manuals ready?Are there delays in loadingfiles?Training program

User-friendly documentation6. Post-implementation andmaintenance_ Evaluation_ Maintenance__ EnhancementsIs the key system running?Should the system be modified?User requirements metUser standards metSatisfied userQ-2 (b) Write several models used to analyze system.Ans There are three models used to analyze system:-


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Waterfall Model for System DevelopmentPrototyping Model

The Spiral Model

Waterfall Model for System Development

In this model, All the steps are followed by each other. An activity starts only when thepreviousactivity has been completed. For example, as per the waterfall model, maintenance phase isstartedonly when the implementation phase has been completed.

Problem

Identification

Feasibility

Study

System

Analysis

System Design

& Coding

Im plementation

Maintenance

Feedback

Waterfall Life Cycle ModelPrototyping

If prototyping is used, the changed requirements are known by the developers at everyiteration. Sinceinformation collection is done at each iteration, new or changed requirements are updatedevery time.

When the final prototype is ready, what do we do with it? We can do two things:_ The prototype can be used as it is, since, it is actually a fully working model._ The prototype can be partially or fully reconstructed. This is done to suit the needs ofimplementing on a specific platform, environment etc.Analyze prototype

Input , processing,

output

Identify us er

requirements

Post

implementation

Implement

prototype

Final

conversion

MaintenanceRevise through

iterative process

Prototyping ModelThe Spiral Model

The spiral model is divided into a number of framework activities, also called task regions.There aresix task regions:_ Customer/user communication: Establish effective communication between developer anduser._ Planning: Define resources, timeliness and other project related information._ Risk analysis: Uses both technical and management risk._ Engineering: Build one or more representations of application.

_ Construction and release: Construct, test, install and provide user support._ Customer evaluation: User provides feedback based on evaluation of software.


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Spiral ModelQ-3 What is System Analyst? Elaborate on the multifaceted role of a system Analyst.Answer:System Analyst:- A system analyst is a person who does all this he identifies activities andobjectivesand determines a procedure to achieve the objectives. The analyst is a person with uniqueskills andput to use these skills to bring together the efforts made by different people in anorganization toachieve business goals.Role of System Analyst:-

(a) System Analyst as an Agent of ChangeIn the role of change agent, the system analyst may select various styles to introducechange to the user organization. when drastic changes are required, it may be necessary toadopt theimposer style. No matter what style is used, the goal is the same; to achieve acceptance ofthe

candidate system with a minimum of resistance.(b) Investigator and MonitorThe role of the investigator is the role of the monitor. To undertake and successfullycompletea project, the analyst must monitor programs in relation to time, cost and quality. Of theseresources,time is the most important. If time "gets away", the project suffers from increased costs andwastedhuman resource.(c) Role of ArchitectAs an architect, the analyst also creates a detailed physical design of the candidate system.He/She aids the user in formalizing abstract ideas and provides details to build the end

product thecandidate system.(d) PsychologistIn system development, it is very important to understanding people thoughts, behavior,be aware of people's feelings and be prepared to get around things in a graceful way. Theart oflistening is important in evaluating responses and feedbacks.(e) System Analyst as Salespersonselling the system to the user. However, selling the system, actually takes place at each stepinthe system life cycle. Sales skills and persuasiveness, then, are crucial to the success of thesystem.

(f) Analyst as MotivatorIt becomes obvious during the first few weeks after implementation and during times, whenturnover results in new people being trained to work with the candidate system.(g) Politician

As much as a politician must have the support of his/her constituency, similar is the analyst'sgoal to have the support of the user's staff. He/She represents their thinking and tries toachieve theirgoal through computerisation.Q-4(a) What do you understand by project selection? Outline the procedure adopted inprojectselection.Answer:Project Selection:- Project selection is not a choice for system analyst but has to analyzedifferent


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requests of different persons from the organization or outside the organization, who aresomehowrelated to the system.The project has to be identified before it can be solved. The basis for an alternative systemisthe recognition of a need for improving an information system or a procedure.The idea for change originates in the environment or within the firm due to any of thefollowingreasons:speed of processing needed to be improvedincreased workloadto cut down on cost of processingrequirement of increased accuracy/reliability of output reports generatedsecurity of processingIt involves following steps:-(i) Project RequestsThere are mainly four primary sources of project requests. The requesters

inside the organization are: Department Managers, Senior Executives andSystem Analysts.(ii) Managing Project Review and SelectionAs the requests come from various departments, someone has to decide whichrequest to pursue and the other to reject.(iii) Preliminary InvestigationThis step involve determine the size of the project, assess costs and benefits ofalternative approaches etc. this phase also check for feasibility analysis ofproject.Q-4 (b) What do you mean by feasibility analysis? Explain economic, technical considerationinfeasibility analysis.

Answer:Feasibility Analysis:- Feasibility Analysis refers to testing capability of a project to find out,whatthe most optimal solution to the problem will be, given the objectives of the problems &constraintsidentified for solving the problem.Economic Feasibility:- It is the most important study that determines the cost & benefits ofthe proposed system & compares with the budget. The cost of the project should notoutweigh thebudget.Technical Feasibility:- During this study, the analyst identifies the existing computer systemof

the concerned department & determines whether these technical resources are sufficient fortheproposed system or not.

Cost/Benefit Analysis:- Cost & benefit Analysis is performed to ascertain, whether the costsin thesystem match with the benefits it will provide. The various kinds of costs incurred in thedevelopmentand implementation of the system include:_Hardware Costs incurred in purchase of hardware, i.e., computer and its peripherals._Personnel Costs include the salaries of the EDP staff, as well as the perks of personnelinvolvedin the development of the system.


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_Facility Costs include expenses incurred in the preparation of the physical site. Thisincludesflooring, wiring, lighting, etc._Operating Costs include all costs associated with the day to day operation of the system._Supply costs include variable costs that increase with increased use of paper, ribbon,disks,etc.System Requirement SpecificationsThe very first step in a system, for the purpose of selection is understandthe requirements within the framework of the organizations objectives.It include flowcharts, input-output requirements, file structure & cost. The specifications mustalsodescribe each aspect of the system clearly, consistently & completely.It also describes the information that is input & output from the system.Conversion:- It means, charging from one system to another.It involves:- (1) Creating computer files(2) Installing Hardware

(3) Training the operating staffFact-Finding:- Fact-finding is the formal process of using research, interviews,questionnaires,sampling and other techniques to collect information about systems, requirements andpreferences. Itis also called information gathering or data collections.During these phases that the analysis learns about the vocabulary, problems, opportunitiesconstraints,requirements, and priorities of a business and a system.How to do Fact-Finding?

For fact-finding, the system analyst does the following:1. Sampling of written (existing) documents

2. On-site observations3. Interview4. Questionnaires5. Research and site visits.6. Rapid Applications Development (RAD)7. Joint Application Development (JAD).8. Observes the current system9. Gather forms and documents currently in use10. Determines the flow of data through the system, and11. Clearly defines the system requirements.

Data Flow Diagrams (DFD):- A DFD, serves the purpose of clarifying system requirements

andidentifying major transformations that will become programs in system design.A DFD, is a representation of various processes and the input and output in each process.Graphical description of a systems data and how the processes transform the data is knownas DataFlow Diagram (DFD).Symbols Used in DFDs_ A square defines a source or a destination of system data. (External entity)._ An arrow identifies data flow data in motion. It is a pipeline through which informationflows._ A circle or a bubble (some people use an oval bubble) represents process that transformsincoming data flow(s) into outgoing data flow(s)._ An open rectangle is a data store data at rest or a temporary repository of data.

Proc ess 1

Sourc e


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Pro cess 2

Des tin ation

Da ta Flow 1 Da ta Flow 4

D ata Flow 2

Data Flow 3

D ata Flow 5

D ata Store

Sample DFDData Dictionary:- A data dictionary is a catalog a repository of the elements in a system.

The majorelements are data flows, data stores and processes. The data dictionary stores details anddescriptionsof these elements.Data Flows:EMP_NO: Char (6)EMP_MASTER4GETEMP_DETEMP_NO EMP_DET

Emp_details: EMP_NA+EMP_ADD+EMP_DOBData Stores:

EMP_RECORD: EMP_NO+EMP_NA+EMP_ADD+EMP_DOBProcess:Do while.not.eof EMP_MASTERopen EMP_MASTERgo topget EMP_DETIf analysts want to know, how many characters are in a data item, and by what other namesit isreferenced in the system, they should be able to find the answers through data dictionary.Components of a Data DictionaryIt contains two types of components are :- data elements and data structures.Data Element:- . Data elements are building blocks for other data in a system. The data

element entryconsists of the following items:_ Data Name_ Data Description: Brief description of what the data element represents_ Aliases or additional names for the data element_ Length or size of the element_ Data Values: It is the list of possible values for the data elementExampleData Name : Part_ColorData Description : This is the color of the part of the machinery and is ordered time to timefrom local vendorAliases : P_Colour, ColorLength : Text of Length 15Data Values : May take one of the following values. Red, Orange, Yellow, Blue,Purple, PinkData Structure:- It is a set of data items that are related to one another.These are built on four relationships of components:-a) Sequence Relationship: Defines the components that are always included in a particulardatastructure; a concatenation of two or more data items.b) Selection (Either/Or) Relationship: Defines alternative data items included in a datastructure.c) Iterational (Repetitive) Relationship: Defines the repetition of a component, zero or more

times.


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d) Optional Relationship: A special case of iteration; data elements may or may not betreatedzero or one time.Decision Analysis

It is a method, which breaks down a problem into parts and allows the user to focus separately on the

critical issues.

Following are the different ways for decision analysis.Decision Tree

Decision tree is a tool where actions need to be taken depending on a number of conditions.If thegroup of conditions has a specific value, a certain action is taken. In such cases, decisiontrees areused. It is a diagram that presents conditions and actions sequentially and thus shows whichconditionsare considered first, which second and so on.ActionConditionAction

ConditionActionConditionActionActionConditionActionConditionAction

The Decision Tree SequenceConditionActionOver $10,000 Take 3% discount frominvoice total

$5,000 - $10,000 Take 2% discountfrom invoice totalWithin ten daysBelow $5,000 Pay full invoice amountPay full invoiceamount

Decision Tree for Discount Authorization.More than 10 days

Decision Table:- A decision table is a matrix of rows and columns, rather than a tree, thatshowsconditions and actions.This method has been used in analysis of business functions, suchas inventorycontrol, sales analysis, credit analysis and transportation control and routing.

Characteristics of a Decision TableIt is made up of four sections: condition statement, condition entries, action statements andactionentries.CONDITIONS DECISION RULES

Condition Condition EntriesAction Action EntriesStatementGENERAL FORM OF A DECISION TABLECondition Decision Rules

1 2 3 4C1. Patient has basic health Y N Y NinsuranceC2. Patient has social health N Y Y N


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insuranceActions

A1. Pay amount of office call XA2. Pay nothing X XA3. Pay full amount of service XCLINIC PAYMENT DECISION TABLESystem design :- It is a transition from a user-oriented document to a document oriented toaprogrammer or data base personnel. It goes through logical & physical design with emphasison thefollowing:-(1) Preparing Input/Output specifications.(2) Preparing security and control specifications.(3) Specifying the implementation Plan.(4) Preparing a logical design walk through before implementation.(5) Review benefits, costs, target dates and system constraints.Objectives:-

Specify the logical design elementsSystem design involves description of detailed design that describes thefeatures of an information system: input, output, files, and databases and procedures.

Support business activities

It supports the business activity for which it is developed. It should alwaysbe secondary to the results the system is intended to produce.

Ensure that system features meet user requirements

The information system meets user needs if it accomplishes the following:- Performs the right procedures properly. Presents information and instructions in an acceptable and effective fashion.

Produces accurate results. Provides an acceptable interface and method of interaction. Is perceived by users as a reliable system.___ Easy to useIt is very easy to use because of some technical features of systemreliability, accuracy and processing speed are secondary to the human aspects of asystem design.___ Provide software specificationsThe specifications state input, output and processing functions & algorithms usedto perform them.___ Confirm to design standardsAs a result, it should be no surprise to learn that well managed

information system groups also maintain systems development standards. System designspecifications are developed within these standards.File design:- Files are the heart of computer application. Constructing, files we mustunderstand the basic types of files used to describe the file hierarchy.Types of file:- Files in which the records are collected and maintained.(1) Master File:- Master files are the most important type of files. It is very significantbecausethey contains the records for maintenance of the organizations business.(2) Transaction File:- A transaction is a temporary file used for two purposes. First of all, it isused to accumulate data about events as they occur.Secondly, it helps in updating master files to reflect the result of currenttransactions. For e.g:- recording of sales.

(3) Table file:- Table files are permanent files containing reference data used in processingtransactions, updating master file or producing output. As the name implies, these files


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store reference data in tabular form.

system analysis and design_nidhi

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