System Analysis and Design

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Published by CFS Documentation CellCentre for Electronics Design and Technology of IndiaAn Autonomous Scientific Society under Department of Electronics,Govt. of India,New Delhi.

First Edition: 1999

TRADEMARKS: All brand name and product names mentioned in this book are trademarks or registered trademark of theirrespective companies.

Every effort has been made to supply complete and accurate information. However, CEDTI assumes no responsibility for itsuse, nor for any infringement of the intellectual property rights of third parties which would result from such use.

No part of this publication may be stored in a retrieval system, transmitted or reproduced in any forms or by any means,electronic, photocopy, photograph, magnetic or otherwise, without written permission of CEDTI.

CEDTI/CFS/99/6/2.1/R1

FOREWORD

The information technology and telecom sectors have suddenly opened up avenues,which require a very large specially trained manpower. These sectors are highly dynamic andneed training and re-training of manpower at a rapid rate. The growing gap of requirement ofthe industry and its fulfillment has created a challenging situation before manpower traininginstitutes of the country. To meet this challenge most effectively, Centre for Electronics Designand Technology of India (CEDTI) has launched its nation-wide franchising scheme.

Centre for Electronics Design and Technology of India (CEDTI) is an AutonomousScientific Society under the Govt. of India, Department of Electronics with its Headquarters atNew Delhi. It operates seven centres located at Aurangabad, Calicut, Gorakhpur, Imphal,Mohali, Jammu and Tezpur. The scheme will be implemented and coordinated by these centres.

The scheme endeavours to promote high quality computer and information technologyeducation in the country at an affordable cost while ensuring uniform standards in order tobuild a national resource of trained manpower. Low course fees will make this educationavailable to people in relatively small, semi urban and rural areas. State-of-the-art training willbe provided keeping in view the existing and emerging needs of the industrial and Govt.sectors. The examinations will be conducted by CEDTI and certificates will also be awardedby CEDTI. The scheme will be operated through all the seven centres of CEDTI.

The CEDTI functions under the overall control and guidance of the Governing Councilwith Secretary, Department of Electronics as its Chairman. The members of the council aredrawn from scientific, government and industrial sectors. The Centres have separate executivecommittees headed by Director General, CEDTI. The members of these committees are fromacademic/professional institutes, state governments, industry and department of electronics.

CEDTI is a quality conscious organisation and has taken steps to formally get recognitionof the quality and standards in various activities. CEDTI, Mohali was granted the prestigiousISO 9002 certificate in 1997. The other centres have taken steps to obtain the certification asearly as possible. This quality consciousness will assist CEDTI in globalizing some of itsactivities. In keeping with its philosophy of ‘Quality in every Activity’, CEDTI will endeavour toimpart state of the art – computer and IT training through its franchising scheme.

The thrust of the Software Courses is to train the students at various levels to carry outthe Management Information System functions of a medium sized establishment, manufactureSoftware for domestic and export use, make multimedia presentations for management andeffectively produce various manufacturing and architectural designs.

The thrust of the Hardware Courses at Technician and Telecommunication EquipmentMaintenance Course levels is to train the students to diagnose the faults and carry out repairsat card level in computers, instruments, EPABX, Fax etc. and other office equipment. AtEngineer and Network Engineer levels the thrust is to train them as System Engineers toinstall and supervise the Window NT, Netware and Unix Networking Systems and repairMicrocontrollers / Microprocessor based electronic applications.

An Advisory Committee comprising eminent and expert personalities from the InformationTechnology field have been constituted to advise CEDTI on introduction of new courses andrevising the syllabus of existing courses to meet the changing IT needs of the trade, industryand service sectors. The ultimate objective is to provide industry-specific quality education inmodular form to supplement the formal education.

The study material has been prepared by the CEDTI, document centre. It is based onthe vast and rich instructional experience of all the CEDTI centres. Any suggestions on theimprovement of the study material will be most welcome.

(R. S. Khandpur)Director General (CEDTI)

TABLE OF CONTENTS

UNIT CHAPTER NAME PAGE NO.

SECTION - A

1 System Concepts and the InformationSystem Environment 11

2 System Development Life Cycle 17

3 System Analysis 21

SECTION - B

4 System Design 29

5 File and Database Design 39

6 System Testing and Quality Assurance 45

PREFACE

Use of Computers, albeit, ‘Information Technology’ has grown tremendously over the last fewyears. It is no longer restricted to scientific applications only. Computers have become allprevasive. Today they affect every aspect of modern business and our personal life.

Computers can improve the performance of all sectors of economy. Therefore, the greatestchallenge of today is to increase business and industry productivity using the full potential ofcomputer-related technology. A systematic study and analysis of any system is an essentialpre-requisite before developing and designing an efficient application software for that system.It is important to master both the methods of system analysis and the skills and tools requiredfor designing the application software. Therefore, System Analysis and Design forms anessential part of any certificate course on Computer Programming.

This course material has been divided into two sections. Section “A” introduces the student tothe system concepts and familiarises him with the basic tools and techniques of system analysis.Life cycle concept consisting of study, design, development and operation has been elaborated.Stress has been laid on the ‘Top Down’ approach for System Analysis. It has been emphasizedthat business is an informaton system and that information is a resource to be managed.

“Section-B” prepares the student to perform activities essential to identifying a computer-based business information system problem and recommending a solution. The Design Phase,teaches the student to perform basic computer-based system design tasks. These tasks includegeneral system design, output design, input design, and file design, including an introductionto database management systems.

Assimilation exercises have been given at the end of each chapter to facilitate the students to

carry out the self check of the level of understanding achieved during the course of the study.

SECTION - A

COMPETENCY OBJECTIVES

The objective of this Section is to introduce the students to one of the most importantaspects of computer programming which is called as System Analysis and Design. At theend of this section, a student should be able to :-

v Logically analyse the importance of System and differentiate between its variousdiscrete components.

v Visualize the activities which complete the System Development Life-Cycleand appreciate the concepts of Operational Evaluation.

v Understand the basic concepts involved in System Analysis.v Analyze, construct and implement the Data Flow-diagrams.v Formulate the graphical representation in the form of decision trees, tables

etc.

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CHAPTER - 1

SYSTEM CONCEPTS ANDTHE INFORMATION SYSTEM ENVIRONMENT

WHAT IS SYSTEM?

System is an orderly grouping of interdependent components according to a plan to advise aspecified task. Its main characteristics are

Organisation Is arrangement of components to achieve objectivesInteraction Interaction refers to the manner in which each component functions

with other components of the system.Interdependence Interdependence means those parts of the organization or computer

systems depend on one another.Integration Integration is concerned with how a system is tied together. It is more

than sharing a physical part or location. It means that parts of thesystem work together within the system although each part performsa unique function. Successful integration will typically produce a betterresult as a whole rather than if each component works independently.

Central objective Central objective is the last characteristic of a system. Objectives maybe real or stated. Although a stated objective may be the real objective,it is quite common that organisation may set one objective and operateto achieve another. The important points is that users must be awareabout the central objective well in advance.

A decision to computerize an application is initiated by user analyzed and designed by analystsprogrammed and tested by programmer and run by operator.

SYSTEM CONCEPTS

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ELEMENTS OF SYSTEM ANALYSIS

SYSTEM CONCEPTS

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TYPE OF SYSTEM

PHYSICAL Systems are tangible entities that may be static or dynamicExample of static - Office desk, ChairExample of Dynamic - Programmed Computer.

ABSTRACT Systems are conceptual or non physical entities. They may be as straightforward as formulas of relationships among set of variables or models is theabstract conceptualization of physical system.

SYSTEM CONCEPTS

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OPEN & CLOSED SYSTEM (INFORMATION SYSTEM)

Open system continuously interact with environment. It interact inputs from and deliversoutput to outside.

Closed system is isolated from environment influence. In reality completely closed systemsare rare.

MAN MADE INFORMATION SYSTEM

Man made information system is a power structure to achieve company goals and classifiedas follows.

1. FORMAL INFORMATION SYSTEM

A Formal information system is based on the organisation represented by the organisationchart. The chart is a map of positions and their authority relationships, indicated by boxes andconnected by straight lines. It is concerned with the pattern of authority, communication andwork flow.

2. INFORMAL INFORMATION SYSTEM

An Informal information system is an employee-based system designed to meet personneland vocational needs and to help in the solution of work-related problems. It also funnelsinformation upward through indirect channels. In this way, it is considered to be a usefulsystem because it works within the framework of the business and its stated policies.

3. COMPUTER BASED INFORMATION SYSTEM

This third category of the information system mainly depend on the computer for handlingbusiness applications. System analysts develop several different types of information sys-tems to meet a variety of business needs. There is a class of systems known collectively asComputer Based Information System. Computer based information systems are of too manytypes. They are classified as:

l Transaction processing System (TPS)l Management Information Systems (MIS)l Decision support system (DSS)l Office Automation Systems (OAS)

The figure 1.2 shows the organisation chart of Computer Based Information System (CBIS)and figure 1.3 shows the hierachical view of CBIS.

SYSTEM CONCEPTS

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Transaction Processing System

A transaction processing system can be defined as a computer based system that capture,classifies, stores, maintains, updates and retrieves transaction data for record keeping andfor input to other types of CBIS. Transaction Processing system are aimed at improving theroutine business activities on which all organisations depend. A transaction is any event oractivity that affects the whole organisation The types of transactions that occur vary fromorganisation to organisation. Transaction processing system provide speed and accuracy andcan be programmed to follow routines without any variance.

EXAMPLE :- Placing orders, billing customers, hiring of employees and depositing chequesare some of the common transactions.

SYSTEM CONCEPTS

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Management Information Systems

Data processing by computers has been extremely effective because of several reasons. Themain reason being the huge amount of data relating to accounts and other transactions canrecord keeping and the automation of routine clerical process. However, in recent years in-creasing attention has been focussed on computer applications providing information for policymaking, management planning and control purposes. MIS are more concerned with manage-ment function. MIS can be described as information system that can provide all levels ofmanagement with information essential to the running of smooth business. This informationmust be as relevant timely, accurate, complete, concise and economically feasible must be asrelevant, timely, accurate, complete and concise as is economically feasible.

Decision Support Systems:

It is an information system that offers the kind of information that may not be predictable, thekind that business professionals may need only once. These systems do not produce regu-larly scheduled management reports. Instead, they are designed to respond to a wide rangeof requests. It is true that all the decisions in an organisation are not of a recurring nature.Decision support systems assist managers who must make decisions that are not highlystructured, often called unstructured or semi-structured decisions. A decision is consideredunstructured if there are not clear procedures for making the decision and if not all the factorsto be considered in the decision can be readily identified in advance.

Office Automation Systems:

Office automation systems are among the newest and most rapidly expanding computer basedinformation systems. They are being developed with the hopes and expectations that they willincrease the efficiency and productivity of office workers-typists, secretaries, administrativeassistant, staff professionals, managers and the like. Many organisations have taken the firststep toward automating their offices.

ASSIMILATION EXERCISES

1. What is the basic difference between “Systems Approach” and “Systems Analysis”?

2. What are the four basic elements in Systems Analysis?

3. What is a Computer Based Information System?

4. When is a decision considered to be unstructured?

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CHAPTER - 2

SYSTEM DEVELOPMENT LIFE CYCLE

System development, a process consisting of the two major steps of systems analysis anddesign, starts when management or sometimes system development personnel feel that anew system or an improvement in the existing system is required. The systems developmentlife cycle is classically thought of as the set of activities that analysts, designers and userscarry out to develop and implement an information system. The systems development lifecycle consists of the following activities:

l Preliminary investigationl Determination of system requirementsl Design of systeml Development of softwarel Systems testingl Implementation, evaluation and maintenance

PRELIMINARY INVESTIGATION

A request to take assistance from information system can be made for many reasons, but ineach case someone in the organisation initiates the request. When the request is made, thefirst system. (activity - the preliminary investigation begins). This activity has three parts:

l Request clarificationl Feasibility studyl Request approval

REQUEST CLARIFICATION

Many requests from employees and users in the organisations are not clearly defined. Therefore,it becomes necessary that project request must be examined and clarified properly beforeconsidering system investigation.

FEASIBILITY STUDY

An important outcome of the preliminary investigation is the determination that systemrequested is feasible. There are three aspects in the feasibility study portion of the preliminaryinvestigation:


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(i) Technical Feasibility: Can the work for the project be done with current equipment, existingsoftware technology and available personnel? If new technology is needed, what is thelikelihood that it can be developed?

(ii) Economic Feasibility: Are there sufficient benefits in creating the system to make thecosts acceptable? Or, are the costs of not creating the system so great that it is advisableto undertake the project?

(iii) Operational Feasibility: Will the system be used if it is developed and implemented? willthere be resistance from users that will undermine the possible application benefits?

The feasibility study is carried out by small group of people who are familiar with informationsystem techniques, understand the parts of the business or organisation that will be involvedor affected by the project, and are skilled in the system analysis and design process.

REQUEST APPROVAL

It is not necessary that all requested project are desirable or feasible. Some organisationsreceive so many project requests from employees that only a few of them can be pursued.However, those projects that are feasible and desirable should be put into a schedule. Insome cases, development can start immediately, although usually systems staff membersare busy on other ongoing projects. When such situation arises, management decides whichprojects are most urgent and schedules them accordingly. After a project request is approved,its cost, priority, completion time, and personnel requirements are estimated and used todetermine where to add it to any existing project list. Later on, when the other projects havebeen completed, the proposed application development can be initiated.

DETERMINATION OF SYSTEM REQUIREMENTS

At the heart of system analysis is a detailed understanding of all important facts of the businessarea under investigation. The key questions are:

l What is being done?l How is it being done?l How frequently does it occur?l How great is the volume of transactions or decisions?l How well is the task being performed?l Does a problem exist?l If a problem exists, how serious is it ? What is the underlying cause?

To answer the above question, systems analysts discuss with different category of persons tocollect the facts about the business process and their opinions of why things happen as theydo and their views for changing the existing process. During analysis, data are collected onthe available files, decision points and transactions handled by the present system. Sometools are used in analysis like data flow diagrams, interviews, on-site observations and


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questionnaires. Detail investigations also require the study of manuals and reports. Once thestructured analysis is completed, analyst has a firm understanding of what is to be done?

DESIGN OF SYSTEM

The design of an information system produces the details that clearly describe how a systemwill meet the requirements identified during systems analysis. systems specialists often referto this stage as logical design, in contrast to the process of developing program software,which is referred to as physical design.

Systems analysts begin the design process by identifying reports and other outputs systemwill produce. Then the specific data on each are pinpointed. The systems design also describesthe data to be input, calculated or stored. individual data items and calculation proceduresare written in detail. Designers select file structures and storage devices, such as magneticdisk, magnetic tape or even paper files. Procedures they write tell how to process the dataand produce the output. The documents containing the design specifications portray the designin many different ways-charts, tables, and special symbols. The detailed design information ispassed on to the programming staff for the purpose of software development. Designers areresponsible for providing programmers with complete and clearly out lined softwarespecifications.

DEVELOPMENT OF SOFTWARE

Software developers may install purchased software or they may develop new, custom designedprograms. The choice depends on the cost of each option, the time available to developsoftware and the availability of programmers. Generally it has been observed that programmersare part of permanent professional staff in a big organisation. In smaller organisation, withoutprogrammers, outside programming services may be hired or retained on a contractual basis.Programmers are also responsible for documenting the program, providing an explanation ofhow and why certain procedures are coded in specific way. Documentation is essential to testthe program and carry on maintenance once the application has been installed.

SYSTEM TESTING

During systems testing, the system is used experimentally to ensure that the software doesnot fail. In other words, we can say that it will run according to its specification and in the wayuser expect. Special test data are input for processing, and the result examined. A limitednumber of users may be allowed to use the system so that analyst can see whether they try touse it in unforeseen ways. It is desirable to discover any surprises before the organisationimplements the system and depends on it.

IMPLEMENTATION, EVALUATION AND MAINTENANCE

Implementation is the process of having system personnel check out and put new equipmentinto use, train users, install the new application and construct any files of data needed to useit. This phase is less creative than system design. Depending on the size of the organisation


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that will be involved in using the application and the risk involved in its use. system developersmay 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 parallel way to compare the result. In stillother situations, system developers stop using the old system one day and start using thenew one the next.

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

(i) Operational Evaluation: Assessment of the manner in which the system functions,including ease of use, response time, overall reliability and level of utilization.

(ii) Organizational Impact: Identification and measurement of benefits to the organisation insuch areas as financial concerns, operation efficiency and competitive impact.

(iii) User Manager Assessment: Evaluation of the attitudes of senior and user manager withinthe organisation, as well as end - users.

(iv) Development Performance: Evaluation of the development process in accordance withsuch yardsticks as overall development time and effort conformance to budgets andstandards and other project management criteria.

Maintenance is necessary to eliminate errors in the working system during its working life andto tune the system to any variations in its working environment. Often small system deficienciesare found as a system is brought into operations and changes are made to remove them.System planners must always plan for resource availability to carry out these maintenancefunctions. The importance of maintenance is to continue to bring the new system to standards.


ASSIMILATION EXERCISES

1. Why is it so critical to manage System Development ? Explain.

2. What are the activities which complete the system development life cycle?

3. In preliminary investigation, three types of feasibility are usually studied. Name those.

4. What are the areas of operational evaluation?

5. Why is maintenance of a system necessary?

6. What important information does the user’s request form provides ? Why is to so importantin the initial investigation? Explain in detail.

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CHAPTER - 3

SYSTEM ANALYSIS

System Analysis is a detailed study of the various operations performed by a system and theirrelationships within and outside the system. One aspect of analysis is defining the boundariesof the system and determining whether a candidate system should consider other relatedsystems.

STRUCTURED ANALYSIS

Structured analysis is set of techniques and graphical tools that allow the analyst to developa new kind of system specifications that are easily understandable to the user. In brief, Thestructured analysis has following attribute.

1. It is logical rather than physical. The elements of system do not depend on vendor orhardware.

2. The process is partitioned so that we have a clear picture of the progression from gen-eral to specific in the system flow.

3. It calls for a rigorous study of the user area - a commitment that is often taken lightly inthe traditional approach to system analysis.

4. It is graphical study which is conceptually easy to understand presentation of the appli-cation.

5. Certain tasks that are normally carried out late in the system development life cycle aremoved to analysis phase. For example, user procedure are documented during analysisrather chain later in implementation

TOOLS OF STRUCTURED ANALYSIS

To keep a blue print (like that of architect) as a starting point for system design, there areseveral tools such as

l Data Flow Diagram (DFD)l Data Dictionaryl Decision Treesl Decision Table

DATA FLOW DIAGRAM

DFD is a way of expressing system requirements in a graphical form A DFD, also known asa bubble chart has the purpose of clarifying system requirements and identifying major trans-formations that will become programs in system design. The DFD does not depend on hard-

SYSTEM ANALYSIS

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ware, software, data structure and file organisation. DFD describes what data flow (logically)rather than how they are processed.

In DFD, there are four symbols:

Square Defines source (originator) or destination of data

Arrow Identifies data flow. It is a pipe line through which information flow.

Circle Represent a process that transforms

or Incoming data flow(s) into outgoing data flow(s)Bubble

Open or Represents a Data store or Data at rest.Rectangle

RULES FOR CONSTRUCTING DFD’s

l Processes should be named and numbered for easy reference. Each name should berepresentative of process.

l Direction of flow is from top to bottom and from left to right..l Arrows should not cross each other .l Squares, circle must be named.

DATA DICTIONARY

Data Dictionary is a structured repository of data about data. It is a set of rigorous of all DFDdata elements and data structures.

ADVANTAGES

Documentation : It is a valuable reference in any organisation

l Improving analysts/ user communication by establishing consistent definitions of vari-ous elements, terms and procedures.

l An important step in building a data base. Most DBMS have a data dictionary as astandard feature.

MAJOR SYMBOLS

= Equivalent to+ And[ ] or / either( ) Optional entry

RULES: Four rules govern the construction of data dictionary entries:

1 Words should be defined to stand for what they mean and not the variable names bywhich they may be described in the program.

SYSTEM ANALYSIS

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2 Each word must be unique; we cannot have two definitions of the same name.3 Aliases or synonym are allowed when two or more entries show the same meaning and

it should be used only when absolutely necessary.4 Self defining words should not be decomposed.

LOGICAL DATA DESCRIPTION HIERARCHY

DATA ELEMENTS DESCRIPTION WITH EXAMPLE

Name POCharacteristics File no.Control information date of origin etc.Physical location in terms of record,

file or data base,

DATA STRUCTURES FOR BOOK DETAIL

DATA STRUCTURES : BOOK DETAILData Elements Author name

Title of book additionISBN (International Standard Book No.)LOCN (Lib of Cong. No)Publisher nameQuantity order

IN SUMMARY

l A data dictionary is an integral component of structured specifications.l Without data dictionary, DFD lacks. rigor and without, DFD data dictionary is of no use.

Therefore, correction between the two is important.

DECISION TREES:

A decision tree helps to show the paths that are possible in a design following an action ordecision by the user. Once the data element are defined in the data dictionary, we begin tofocus on the processes

Example : Book - Order

SYSTEM ANALYSIS

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Book stores get discount of books acquired from publishers, we can expect one lower-levelprocess to verify the discount.

DISCOUNT POLICY

Book store gets trade discount of 25%; for orders from libraries and individuals 5% allowed onorder of 6- 19 copies per book title,

10% on 20 - 4915% on 50 or more

DECISION TREE

For above referred example, shall be as under

Type of Customer Size of Order Discount

Book store 6 or more - 25%less than 8 - Nil

Discount Policy50 or more - 15%

Libraries 20 - 49 - 10%or 6 - 19 - 5%Individuals less than 6 - Nil

DECISION TABLES

Major draw back of a decision tree is the lack of information in its format to tell us what othercombinations to test.

l A decision table is a table for contingencies for defining a problem and actions to betaken

l It is a single representation of relationships between conditions and actions

TITLE : DateAuthor: SystemComments:

Condition Stub Condition Entry

Action Stub Action Entry

EXAMPLE : DECISION TABLE FOR BICYCLE ASSEMBLY:

SYSTEM ANALYSIS

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TITLE : Bicycle Assembly DATE :Author: System:Comments : More than one carton of parts needs to be assembled

1 2 3 4

1. Last Carton? y y n n2. Hand Brakes? y n y n

1. Open Container . . x x2. Stack Parts . . x x3. Assemble whells . . x x4. Finish assembly . . x x5. End of assembly operations x x . .

SYSTEM ANALYSIS

DECISION TABLE FOR BICYCLE ASSEMBLY

Where Y= Yes, N = No, X = Response to the answer entered in the condition entry quadrant

So, according to the decision table we have sit decision and therefore provides each decision(answer) immediately.

Rules for constructing a decision table

l A decision should be given a name, shown in the top left of the table.l The logic of the decision table is independent of sequence in which the condition rules

are written, but the action takes place in order in which the events occur.l Standardized language must be used consistently.l Duplication of terms or messages should be eliminated where possible.

In brief we can summarize the tools for system analysis as :

DFD - May be used at low or high levels of analysis and provide good system documenta-tion. The user often finds it confusing

DATA DICTIONARY

May be used at high or low level of analysis but it does not provide functional details, and it isnot acceptable to many non technical users.

DECISION TREE

Used to verify logic and in problems that involve complex decision resulting in limited numberof action

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SYSTEM ANALYSIS

DECISION TREE & TABLE

Are best suited for dealing with complex branching routines such as calculating discounts orsales commission or inventory control procedures.

EXAMPLE

Figure 3.1 shows the decision tree for printing the accounts payable check. Trees can beeasily read by non technical users who find decision table too complex. users readily graspbranches, forks, and out comes.

ASSIMILATION EXERCISE

1. Illustrate the difference between input/output analysis and system flowcharts. When iseach tool used ?

2. What are data flow diagrams? How do they differ from structure charts ?

3. Why is it important that the analyst learns about an organization’s policies and objectives?

4. What traditional information-gathering tools are available for the analyst? Explain eachtool briefly.

5. What kinds of data should be recorded ? Why ?

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SECTION - B

COMPETENCY OBJECTIVES

The objective of this Section is to introduce the students to one of the most importantphases in System Analysis and Design. At the end of this section, a student should be ableto :-

v Visualize the requirement for System Design to meet the Design objectives.v Work upon the various Design methodologies and utilize them effectively to

generate efficient results.v Understand the factors that have to be considered in the Form Design.v Formulate and use the File Organization and Database Design effectively in

their practical implementation.v Perform the System Tests and checks for the sub-standard performance levels

or the other factors which lead to the system failure.v Appreciate the importance of Quality and achieve the goal of Quality Assurance

in System Life-Cycle.

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l System design is a solution, a how to approach the creation of a new system.l System design goes through logical and physical stages of development.l Logical design review the present physical system, prepare input and output specifications

makes security and control specifications details the implementation plan and preparesthe logical design walk through

l Physical design produces actual program S/W, file, and a working system.

DESIGN OBJECTIVES

Practicallity - System must be stable & operated by person of average intelligenceCost - Desirable to aim for system with minimum cost flexibility/ portabilitySecurity - Include security feature to the system developed.

LOGICAL DESIGN

l Review the current physical system - its data flow, file content . etc.l Prepares output specification - i.e. determines the format ,content and frequency of

reports including terminal specification and location.l Prepares input specification format, content and most of the input functionsl Prepares edit, security and control specification- This includes specifying rules for edit

correction backup procedures and controls that ensure processing and file integrity.l Specifies implementation plan.l Reviews benefits, costs, Target dates and system constraints.

PHYSICAL DESIGN

It consisting of

# Design the physical system* Specify input/output media* Design database and specify backup procedures* Design physical information through system and physical design walk through

CHAPTER - 4

SYSTEM DESIGN

SYSTEM DESIGN

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# Plant system implementation* Prepare a conversion schedule and target date.* Determine training procedure course and time table

# Devise a test and implementation plan and specify any new Hardware/Software.

# Update benefit, cost conversion date and system constraints (legal financial,hardware etc.)

DESIGN METHODLODOGIES ATTEMPT TO DO THE FOLLOWING

* Improve productivity of analyst and programmer.* Improve documentation and subsequent maintenance and enhancements* Cutdown drastically on cost overruns and delays.* Improve communication among the user, analyst, designer and programmer.* Standardize the approach to analysis and design* Simplify design by segmentation

SYSTEM DESIGN

FilesMatrices

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STRUCTURED DESIGN

Structured design is a data flow based methodology.

l System specifications are then used as a basis for graphical representation action i.e.DFD.

l From DFD, next step is definition of modules and their relationship to one another calledstructured chart, using a data dictionary and other structured tools.

l Structured design partitions a program into small independent modules.

STRUCTURE CHART

Graphic tool for representing hierarchy and it has three elements

= a module

Connection means one module has calledanother represented by a vector linking themodules.

Were O, P and Q are coupled

Couple is represented by an arrow with circulartail. It representes data elements moved from onemodule to another.

FORM DRIVER METHODOLOGY

HIPO is a form driver technique used to document the information.

l It consists of hierarchy chart and an associated set of input/process/output charts.l It describes the data input and output from process and defines the data flow com-

position. It was developed by IBM with following objectives.t Provides a structure by which the function of a system can be understood.t State the functions to be performed by the program rather than specifying the

program statements to be used to perform the function.

A

B C

A

B C

O Q

P

SYSTEM DESIGN

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t Provide a visual description of input to be used and output to be produced foreach level of diagram.

PROCEDURE FOR GENERATING HIPO DIAGRAMS

l Begin at the highest level of abstraction and define the inputs to the system and O/P from it in aggregate terms.

l Identify the processing steps by those that convert I/P into O/Pl Document each element using HIPO diagram notation and associated tree like

structure.l Identify sub processes and their respective inputs and outputs. Continue decompo-

sition until the process cannot be decomposed any further.

Aids available for drawing HIPO diagrams are

HIPO Worksheet GX 20-1970HIPO Template GX 20 - 197Contains symbols for HIPO

HIPO package format consists of VIOC (Visual Table of Constant) shows the structure ofdiagram and relationships of functions in a hierarchical manner. It also has a legend to showhow symbols are to be used.

Overview diagrams describes major functions and reference the detail diagram needed toexpand the functions adequately.

Input Process OutputContains Contains Data item createdData items members by process stepused by process steps and functions

to be performed.

Detail Diagram contains an extended description section that amplifies the process step andreference the code associated with each step process.

SYSTEM DESIGN

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I/P DESIGN - Is the process of converting user originated inputs to a computer basedformats.

INPUT DATA - Goal of designing I/P data is to make data entry as easy, logical and freefrom errors as possible, In entering the data, operators need to know.

- allocated space for each field- field sequence- format in which data fields are entered e.g. filling out data field is required through

the edited format mm/dd/yy

SOURCE DOCUMENT

Initiate the processing cycle as soon as they are entered on the system. Sources may beentered into the system from punch cards, diskettes or even directly through keyboards there-fore source document may be evaluated in terms of

- its continued use in the proposed system- extent of modification for the proposed system &- replacement by an alternative source document.

A source document should be logical and easy to understand e.g. date of birth

Ist May 1963May 1 19635/1/63 (American)1/5/63 (European)

source document should specify mmddyy

INPUT MEDIA & DEVICES

These are as follows :Punch CardsCRT ScreenOCR (Optical Character Recognition)Mark sensing readerMICR translates special fonts printed in magnetic ink on checks and Direct computer

input through keyboard.

VALIDATION TEST :- A system can employ any of nine common validation tests:

1. Class Test NumericAlphabetic

2 Sign Test Determines weather algebraic value of numeric date is <, > or= to zero

SYSTEM DESIGN

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3. Reasonableness Test Rejects data that should never occur4. Sequence Test Ensures that data appears in a certain order mmddyy5. Range Test Determines that data falls within upper & lower limit

e.g. month between 1- 126. Presence Test Ensures that data are present to allow further processing (Drug

No.)7. Code Test Data values must match one of the several acceptable prede-

termined values (year 91 - 93,94 etc)8. Combination Test A certain group of data elements must be present at the same

time and must be correct drug no., dosage, date and patientno. must all appears

9. Date Test Requires two digit month, day, and two digit year no.

GUIDE LINES FOR DATA ENTRY SCREENS

- Keep screen simple- Make screen easy to read.- Position the cursor to the first field in which user will enter the data- Use same color for similar elements e.g. red for error, green for money etc.- Use consistent method for signaling error messages.- Place error messages in the same place on every screen.- Include passwords to tighten security- Use same format throughout the project.- provide help or tutorials for technical terms or procedures.

OUTPUT DESIGN

Computer O/P is the most important and direct source of information to the user. Efficientintelligent O/P design should improve the system relationships with the user and help indecision making. A major form of output in hardcopy from the printer. Print outs should bedesigned around the output requirements of the user. Following guidelines apply to any re-port.

* Information should be clear and accurate, yet concise and restricted to relevantdata

* Report should have titles, date, descriptive headings for columns of data num-bered pages and so on.

* Report should be in a logical arrangements so that users can easily locate whatthey need.

* The report should come on an output medium that best suits the user’s need (stock-broker - CRT, Manager Printout)

SYSTEM DESIGN

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INTERNAL REPORTS

Manager & other decision making within organisation use internal report to track performanceand to make variety of business judgements,

EXTERNAL REPORTS

Circulate among customers, clients, stockholders vendors, Govt. agencies and others outsidean organisation. Since the report present company’s image outside the world, they mustmake company well organised, stable and professional.

OUTPUT DEVICES

Printer- Selected in respect of- Amount of O/P work per week per month (device speed)- Quality of output- Existing printer’s available

List Requirements- Except for customers, reports need not be elegant, most would circulate internally- 12000 page per month printouts i.e. 4,80,000 lines.- Organisation does not need a plotter that could draw graphs- Payroll forms could be oversized (132 character).

Paper

Important consideration cost, no. of copies needed based on these factors, analysts select:

- Weight & bond of paper- Plain paper or preprinted paper

CRT- Appearance of materials on the screen monochrome color.- Screen size (diagonal measure in inches 14") VGA, SVGA etc.

DESIGN OF OUTPUT REPORTS

Most reports contain all or some of the following design elementsReprot heading - Title of reportPage Heading - Page number, Date, Time, etc.Control Heading - Captions & titles that separate one group of data from another.Column Heading - Heading is given in each column.Detail Line - Details about each column heading is givenControl Footing - Appearing at bottom of the Page

SYSTEM DESIGN

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FORM DESIGN & CONTROL

Form is a tool with message. It is the physical carrier of data or information

order, instruction,authorizes i.e.applied for P.O.

Action form - Achieves results Sales Slip etc.Goes from one place to another

Represent i.e. library recordsMemory Form - historical data

Data generally used forreference in a file

- Summary picture of project i.e. balance sheetReport Form - Provides info about job details & report trial balance sheet

- Used by manager with authority etc.to effect change

FACTORS TO BE CONSIDERED IN FORM DESIGN

l Size and shape of the form should be such that it is convenient for handlingl Max. readability & use physical factors - color type of paperl each of data entryl Carbon paper as form copies, one time carbon, carbon backed paper, no. of car-

bon required paper

SYSTEM DESIGN

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ADVANTAGES DISADVANTAGES

SEQUENTIAL Simple to design easy to program Records cannot be added atvariable length record best use of middle.storage space

INDEXED Records can be added at middle Unique key require slow SEGMENT Processing can be carried out processing

Sequentially or randomly

INVERTED LIST Used in application requestingspecific data on multiple keys.

RANDOM Records can be inserted or updated inmiddle of file better control over recordallocation.

SYSTEM DESIGN


1. In your own words, describe the process of system design.

2. Distinguish between the following:

a. Logical and physical design

b. Coupling and cohesion

3. What design methodologies are used in system design ?

4. Define structured design. How is it related to a DFD ?

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CHAPTER - 5

FILE & DATA BASE DESIGN

ABOUT FILE

File is a particular group of information collected at a common place, making information easyto retrieve and store with day to day basis.

To learn about files we need to define basic terms of the file hierarchy

BYTE

A byte is an arbitrary set of eight bits that represent a character. It is the smallest address-able unit in today’s computer.

DATA ITEM

One or more bytes are combined into a data item to describe an attribute of an object. Forexample, if the object is an employee one attribute may be sex, name, age or social securitynumber. A data item is sometimes referred to as a field. A field is actually a physical space ontape or disk, whereas a data item is the data stored in the field.

RECORD

Collection of related data items. There are two types of records

(i) Logical record(ii) Physical record

A logical record maintains a logical relationship among all the data items in the record. It isthe way the program or user sees the data. In contrast, a physical record is the way data arerecorded on a storage medium. To illustrate, Figure 5.1 shows a programmer who required afive - record file in a particular sequence (A,D,C,B,S). The programmer does not know aboutthe physical “map” on the disk. the software presents the logical records in the required se-quence. This capability is unique to data base design.

FILE & DATABASE DESIGN

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FILE

Collection of related records. It characteristics are

(i) Activities(ii) Volatility

File activity specifies the percentage of actual records processed in a single run. If a smallpercentage of records is accessed at any given time, the file should be organized on disk fordirect access. In contrast, if a fair percentage of record is affected regularly, then storing thefile on tape would be more efficient and less costly. File volatility addresses the properties ofrecord changes. File records with substantial changes are highly volatile, meaning that diskdesign would be more efficient than tape.

DATABASE It is a set of interrelated files for real time processing. It contains thenecessary data for problem solving and can be used by several usersaccessing data concurrently.

TYPE OF FILE File can be permanent files containing reference data used in pro-cessing transactions, updating master files or producing O/P. Thesefiles store data in tabular form.

REPORT This type of file gives relevant information from the data base file afterthe processing of the data. If the report file information is to be usedfor internal use only the relevant option is shown. But if report is to beused externally all the information in a beautiful format is given to theuser.

BACKUP Copy of master, transaction or table file that is made to ensure a copyis available if anything happens to the original.


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FILE ORGANISATION

Sequential - Record can be added only at the end of the file. It is not possible to insert a recordin the middle of file without rewriting. The file

- No address or location assignments in.- Simple to design

INDEXED SEQUENTIAL

- Having address or location assignments- Permits next and economical use of sequential processing techniques when activ-

ity rate is high.- Sequential- Have multiple index for a given key


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INVERTED LIST

- Records are not necessarily stored in sequence .- Have single index for each key type.

Defined on keys and separate index is maintained for each

DIRECT ACCESS

Data are placed randomly

- record need not be in sequence become they are updated directly and rewrittenback in the same location

- New records are added at the end of file or specific location based on S/W com-mands

DATA BASE DESIGN

- A Database can be thought of as set of logically related files organised to facilitateaccess by one or more application program and to minimize the data redundancy.

OBJECTIVE OF DBASE

- To make information access easy quick, inexpensive and flexible for the user- Controlled redundancy- Data independence- Lower cost- Accuracy and integrity

Following figure shows the total Data Base Mangement System.

This block diagram shows the collection of data1. for various cities in north, south, east, and west2. pin code of cities.3. peoples living in these cities4. .....5. .........and many more information as per users need.

The use of DBMS package (such as ORACLE, FOXPRO dBASE) are to be used for process-ing of data as per user need.


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1. Illustrate the hierarchy making up a database.

2. Explain the difference between:

a. Logical and physical record.

b. Data item and field

c. File activity and file volatility.

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CHAPTER - 6

SYSTEM TESTING AND QUALITY ASSURANCE

What is system testing?

System testing is executing a program to check logic changes made in it and with the intentionof finding errors- making the program fail proof. Testing is essential to the success of thesystem

In system testing, performance and acceptance standards are developed. Substandardperformance or service interruptions that result in system failure are checked during the test.The following performance criteria are used for system testing.

1. Turn around time is the elapsed time between the receipt of the input and the availabilityof the output.

2. Backup relates to procedures to be used when the system is down.3. File protection pertains to storing files in separate area for protection against fire, flood,

or natural disaster.4. The human factor applies to the personnel of the candidate system

TYPE OF SYSTEM TESTS

System testing consists of the following steps.

1. Program(s) testing2. String testing.3. System testing.4. System documentation5. User acceptance testing.

PROGRAMS TESTING

A program represents the logical elements of system. Program testing checks for two types oferrors: syntax errors and logic errors. A syntax error is a program statement that violates oneor more rules of the language in which it is written. These errors are shown through errormessages generated by the computer. A logic error on the other hand deals with incorrectdata fields, out-of-range items, and invalid combination.

SYSTEM TESTING & QUALITY ASSURANCE

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STRING TESTING

Program are invariably related to one another and interact in a total system. Each program istested to see whether it conforms to related programs in the system. Each portion of thesystem is tested against the entire module with both test and live data before the entiresystem is ready to be tested.

SYSTEM TESTING

System testing is designed to uncover weaknesses that were not found in earlier tests. Thisincludes forced system failure and validation of the total system as it will be implemented byits user(s) in the operational environment.

SYSTEM DOCUMENTATION

All design and test documentation should be finalized and entered in the library for futurereference. The library is the central location for maintenance of the new system. It verifies thatthe system’s procedures operate to system specification and that the integrity of vital data ismaintained . Performance of an acceptance test is actually the user’s show. User motivationand knowledge are critical for the successful performance of the system.

QUALITY ASSURANCE

Quality assurance defines the objectives of the project and reviews the overall activities sothat errors are corrected early in the development process. Steps are taken in each phase toensure that there are no errors in the final software.

GOAL OF QUALITY ASSURANCE IN SYSTEM LIFE CYCLE

The goal of this stage is to define the factors that contribute to the quality of the candidatesystem. Several factors determine the quality of a system:

1. Correctness The extent to which a program meet system specification anduser objectives.

2. Reliability The degree to which the system performs its intended functionsover a time.

3. Efficiency The amount of computer resources required by a program toperform a function.

4. Usability The effort required to learn and operate a system.5. Maintainability The ease with which program errors are located and corrected.

6. Testability The effort required to test a program to ensure its correctperformance.

7. Portability The ease of transporting a program from one hardwareconfiguration to another.

8. Accuracy The required precision in input editing, computations, andoutput.

9. Error tolerance Error detection and correction versus error avoidance.10. Expandability Ease of adding or expanding the existing data base11. Access control Control of access to the system and extent to which that access

can be and audit audited.


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12. Communicativeness How descriptive or useful the inputs and outputs of the systemare.

LEVELS OF QUALITY ASSURANCE

There are three levels of quality assurance:

1. System Testing2. System Validation3. Certification

SYSTEM TESTING

In the system testing the common view is to eliminate program errors. This is extremely difficultand time-consuming, since designers cannot prove 100 percent accuracy. Therefore, all thatcan be done is to put the system through a “fail test” cycle- determine what will make it fail. Asuccessful test, then is one that finds errors. The test strategies discussed earlier are used insystem testing.

SYSTEM VALIDATION

System validation checks the quality of the software in both simulated and live environments.First the software goes through a phase (often referred to as alpha testing) in which errorsand failures based on simulated user requirements are verified and studied. The modifiedsoftware is then subjected to phase two (called beta testing) in the actual user’s site or a liveenvironment. The system is used regularly with live transactions. After a scheduled time,failures and errors are documented and final correction and enhancements are made beforethe package is released for use.

SYSTEM CERTIFICATION

The third level of quality assurance is to certify that the program or software package iscurrent and conforms to standards. With a growing trend towards purchasing ready-to-usesoftware, certification has become more important. A package that is certified goes through ateam of specialists who test, review and determine how well it meets the vendor’s claims.Certification is actually issued after the package passes the test certification, however, doesnot assure the user that it is the best package to adopt; it only attests that it will perform whatthe vendor claims.

TRENDS IN TESTING

Automated tools and software aids are used for testing. Tools are as under

1. FUNCTIONAL TESTER

The functional tester is of great value when minute hardware problems are disguised assoftware bugs. For Example, hardware faults are usually repeatable, whereas software bugsare generally erratic. Problems arise when the delicate interaction between hardware andsoftware cause a hardware problem to appear as an erratic software bug. A functional testerdetermines immediately that the problem is in the hardware. This saves considerable timeduring testing.


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2. DEBUG MONITOR

Another software aid is the debug monitor. It is a computer program that regulates and modifiesthe applications software that is being tested. It can also control the execution of functionaltests and automatically patch or modify the application program being tested.

The use of these tools will increase as systems grow in size and complexity and as theverification and insurance of reliable software become increasingly important.

ROLE OF THE DATA PROCESSING AUDITOR

The data processing (DP) auditor should be involved in most phases of the system life cycle,especially system testing. In the past, auditors have audited system after they have beeninstalled. Then the cost is often too prohibitive to go back and modify the system to incorporateadequate control. Therefore audit control must be built into the system design and tested withthe cooperation of both the analyst and the DP auditor. The auditor’s role is to judge thecontrols and make recommendations to the system team in charge of the project. The userdepartment should participate in reviewing the control specification for the system to ensurethat adequate control has been provided.

THE AUDIT TRAIL

An important function of control is to provide for the audit trail. In designing tests the auditor isconcerned about the changing nature of the audit trail.

Some of the following changes in the audit trail confront the auditor

1. Source documents are no longer used by the system after they are transcribed onto amachine-readable medium.

2. Files stored on tape or disk can be read only be a computer, which limits the auditingfunction.

3. Processing activities are difficult to observe, since most of them are within the system.

MAINTINING OF AUDIT TRIAL

One way to maintain a viable audit trail is to keep a detailed file of the transactions as theyoccur. The file can then be the input for an audit program that extracts the transactions forselected accounts and prints them so that auditor can trace the status of an account in detail.



1. Why do we test systems ? How important is testing ? Elaborate.

2. A variety of tests are used to test systems. Discuss three such tests.

3. What types of test data are used in system testing ?

4. Specify the purpose of system testing. What performance criteria are used for sys-tem testing? Discuss.

Documents

System Analysis and Design