System Analyses and Design

8/8/2019 System Analyses and Design

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SYSTEM

ANALYSIS

A ND DESIGN


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Chapter-1

SYSTEM CONCEPT

System ConceptA system is a way of thinking about the organization and their problems. It also involves a

set of techniques that helps in solving the problems.

The term system is derived from the Greek word systema which means an organized

relationship among functioning units or components. A system exists because it is designed

to achieve one or more objectives.

A system is an orderly grouping of the interdependent components linked together

according to a plan to achieve a specific objective. The word component may refer to the

physical parts, managerial steps or a subsystem in a multilevel structure. The components

may be simple or complex, basic or advanced. Each component is a part of the total system

and has to do its share of the work for the system to achieve the intended goal. This

orientation requires an orderly grouping of the components for the design of a successful

system.

The study of the system concept has three basic implications: -

1- System must be design to obtain a predetermined objective.2- Interrelationship and interdependency must exist among the system components.3- The objective of the organization as a whole must have a higher priority than the

objective of its subsystem. Another way to view system is as shown in the figure:


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Goal setting is one of the principles which exactly define but the system is supposed

to do.

System boundary defines the components that make of the system. The set of system

component can be changed during the system design. Anything outside the system

boundary is known as the system environment. Things outside the system study can affect

the system behavior. A system can be made of any number of subsystems. Each subsystem

carries out parts of the system function. Subsystems are important because they can help to

handle system complexity and thus improve the understanding of the system. Each

subsystem carries out some parts of the system objective.

Feedback is the identity of monitoring the current output and comparing it to the system

goal.

Feedback uses variation from a system goal to change system behavior.

Monitoring a system checks the e-mail to see if a system is meeting its goal.

Any variation from the goal are then feedback into the system and used to adjust it to

ensure that it meet its goal. To do this it is necessary to monitor the system to see if it is

meeting its goal.

Characteristics of a system

1-Organization: - Organization implies the structure and order. It is an arrangement of

components that helps to achieve the objectives. In the design of a business system for


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example: - the hierarchical relationship starting with the president on the top and leading

downward to the workers represents the organization structure. Such an arrangement

portrays a system- subsystem relationship defines the authority structure specifies the

formal communication and formalizes the chain of command.

2- Interaction: - Interaction refers to the manner in which each component function

with other components of the system. In an organization for example: - purchasing must

interact with production, advertising must interact with sale and payroll with personnel. In

a computer system a central processing unit must interact with the input device to solve a

problem. In turn the main memory holds program and data that the arithmetic unit uses for

the computation. The interrelationship between these components enables the computer to

perform.3-Interdependence: - It means that the parts of the organization or computer system

depend on one another. They are co-ordinate and linked together according to a plan. One

subsystem depends on another subsystem for proper functioning. The output of one

subsystem is the required input for another subsystem. This is called interdependence in

systems work.


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The above figure shows three levels of subsystem. Each of the top inner circles represents

the major subsystem of a production firm. The personal sub system, in turn, may be viewed

as a system that consists of subsystems such as benefits, health and safety, and employment

health and safety key. Personal sub system consists of lower level elements that areconsidered vital in personal operation. Each element may be represented by a computer

based package and is a part of human resource data base that provides information or

unemployment, insurance benefits and the like. In short no sub system can function in

isolation because it is dependent on the data (inputs) it receives from the other subsystem to

perform its required task. A decision to computerize an application is initiated by the user,

analyzed and designed by the analyst, programmed and tested by the programmer and done

by the computer operator.


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Task independence in a computer based sub system

4- Integration: - Integration is concerned with how a system is tied together. It is more

than a topic. It is more than sharing a physical part or location. It means that the parts of thesystem work together within the system even though each part performs a unique function.

Successful integration will typically produce a good affect and greater total impact than if

each component works separately.

5- Central objective: - The last characteristic of a system is central objective. Objective

may be real or stated. Although the real objective may be the real objective, it is not

uncommon for an organization to state one objective and operates to achieve another. The

important point is that users must know the central objective of a computer application

early in the analyses for successful design and conversion.


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Chapter-2

Elements of a System

Elements of a System

1- Outputs and inputs2- Processor3- Control4- Environment5- Feedback6- Boundaries and interface

Outputs and Inputs: - A major objective of a system is to produce an output that has value

to its user. Whatever the nature of the output (goods, services, information) it must be in

line with the expectation of the intended user. Inputs are the elements (material, human,resources and info) that enter the system for processing. Output is the outcome of the

processing. A system feeds on input to produce output in much the some way that a

business brings in human, financial and material resources to produce goods and services.

It is important to point out that determining the output is a first step in specifying the

nature, amount and regularity of the input needed to operate a system. For example: - in

system analyses the first concern is to determine the users requirement of a proposed

computer system. That is specification of the output that the computer is expected to

provide for meeting users requirement.

Organizations environment


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Organizations environment

Processor: - The processor is an element of a system that involves the actual

transformation of the input into the output. It is the operational component of a system.

Processor may modify the input totally or partially depending on the specification of the

output. Thus means that as the output specification changes so does the processing. In some

cases input is also modified to enable the processor to handle the transformation.Control: - The control element guides a subsystem. It is a decision making subsystem that

controls a pattern of activities governing input, processing and output. In an organizational

context management as a decision making body controls the inflow, handling and outflow

of the activities that affect the welfare of the business. In a computer system the operating

system and the accompanying software influence the behavior of the system. Output

specification determines what and how much input is needed to keep the system in balance.

In system analysis knowing the attitude of the individual who can control the area

for which a computer is being considered can make a distance between the success and

failure of the installation. Management support is required for securing control and

supporting the objective of the proposed change.


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Feedback: - Control in a dynamic system is achieved by feedback. Feedback measures

output against a standard in same form of cybernetic processor that includes

communication and control.

Feedback may be positive or negative, routine or informational. Positive feedback

reinforces the performance of the system. It is routine in the system. Positive feedback

generally provides a controller with the information for action. In system analysis feedback

is important in different ways. During analysis the user may be told that the problems in the

given application verify his or her initial concern and justify the need for change. Another

form of feedback comes after a system is implemented. The user informs the analyst about

the performance of the new installation this feedback often results in enhancement to meet

the user requirements.

Environment: - The environment is the supra system with which an organization

operates. It is the source of external elements that influence a system. In fact it often

determines how a style must function.

Boundaries and interface: - A system should be defined by its boundaries that the limits

that identify its components, processes and interrelationship when it interfaces with other

system.

Each system has boundaries that determine its sphere of influence and control. In system

analysis knowledge of a given system is crucial in determining the nature of its interface

with other systems for successful design.

Types of system

Systems have been classified in different ways. Common classifications are following: -

1- Physical or abstract2- Open or closed3- Man made information system

Physical or abstract system: - Physical systems are tangible entities. They may be static

or dynamic in operation. For example: - The physical parts of the computer system are the

offices, desks, chairs that facilitate operation of the computer. They can be seen or counted.


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They are static. In contrast a computer system is a dynamic system. Data, programs, output

and application changes as a user demand or the priority of the information changes.

Abstract systems are conceptual or non physical entities. They may be as straightforward as

formulae of relationship among sets of variable or models; the abstract conceptualization of

physical situation. A model is a representation of a real or planned system. The major

models are: -

1- Schematic model: - A schematic model is a two dimensional chart depicting systemlanguage.

2- Flow system model: - A flow system model shows the flow of the material, energyand information that hold the system together.

3- Static system model: - This type of model exhibits one pair of relationship such asactivity time or cost quantity.

4- Dynamic system model: - Business organizations are dynamic system. A dynamicmodel approximates the type or organization or application that analyst deals with.

Open or closed system: - This classification of system is based on their degree of

independence. An open system has many interfaces with its environment. It permits

interaction across its boundary. It receives input from and delivers output to the outside. An

information system falls into this category since it must adapt to the changing demand of

the user. In contrast a closed system is isolated from environmental influence. In reality a

completely closed system is rare. In system analysis organizations, computers and

applications are invariably open. Dynamic systems influenced by their environment.

Important Characteristics of Open System

1- Input from outside: - Open systems are self adjusting and self regulating. Whenfunctioning properly an open system reaches a steady state or equilibrium.

In a retail firm for example: - A steady state exist when goods are purchased and

sold without being either out of the stock or overstock. An increase in the cost of

the goods forces a comparable increase in prices or decrease in operating cost. This

response wills the firm its the steady state.


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2- Entropy: - All dynamic systems tens to run down over time result in entropy or lossof energy. Open system resist entropy by seeking new inputs or modifying the

processes to return to a steady state.

3- Process, output and cycles: - Open system produce useful output and operate incycles and following a continuous flow path.

4- Differentiation: - Open systems have a tendency towards and increasingspecialization of functions and a greater differentiation of their components. In

business roles of peoples and machines tens towards greater specialization and

greater interaction.

5- Equifinality: - The term implies that goals are achieved through differing course ofaction and a variety of paths. In more systems there is more stress on goals than on

paths to reach the goals. Understanding system characteristics help analyst to

identify their role and relate their activities to the attainment of the firms objective.

Man Made Information System: - An information system is the basis for the interaction

between the user and the analyst. It provides instruction commands and feedback. It

determines a nature of the relationship among decision makers. An information system may

be defined as a set of devices processors and operating system designed around user based

criteria to produce information and communicate it to the user for planning, control and

performance. The major information systems are formal, informal and computer based.

1- Formal Information System: - A formal information system is based on theorganization represented by the organization chart. The chart is the map of position

and their authority relationship indicated by boxes and connected by straight lines.

It is concerned with the pattern of authority, communication and workflow.

Information is formally disseminated in instructions, memos or reports from tap

management to the intended user in the organization. This structure also allows

feedback up the chain command for follow up. Policies are generalization that

specifies what an organization out to do. Policies are translated into directives, rules

and regulations and transmitted to lower level management for implementation. The

output represents employee performance.


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Categories of Information: - There are three categories of information related to manage a

level the decision manager make.

The first level is Strategic Information, which relates to long range planning policies that

are of direct interest to upper management. Information such as population growth tens in

financial investment and human resource changes would be off interest to top company

official who are responsible for developing policies and determining long range goals. For

ex: - DSS (decision support system).

The second level of information is Monitorial Information. It is of direct use to middle

management and department head for implementation and control. For example: - sales

analysis cash flow projection and annual financial statement. This information is of use in

short and intermediate range. It is maintained with the aid of MIS (management

information system).

The third information level is Operational Information which is short term; daily

information used operate department on enforce the day to day rules and regulations of the

business operation. For example: - daily employee absence sheet, overdue purchased orders

and current stock available for sale. Operational information is established by DPS (data

processing system).


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2- Informal Information System: - Informal information system is an employee basedsystem designed to meet personal and vocational needs and to help solve work

related problems. It is a useful system because it works within the frame work of

the business and its stated policies. Knowledge about the inner working of the

employee based system is useful during the exploratory face of the analysis.

Employee co-operation and participation are crucial in training users. Since

computer cant provide reliable information without user staff support, a proper

interface with the informal communication channels could mean the difference the

between the success and the failure of the system.

3- Computer Based Information System: - A third class of the information systemrealize on the computer for handling the business applications.

Management Information System (M I S): - The computer has a significantimpact on the technique used by management to operate the business. The level

of the manager in the organization is also a factor in determining the kind of

information needed to solve a problem. Lower level management needs

detailed internal information to make day to day relatively structured controlled

decisions higher level management. For whom the long range objectives are the

primary concerns requires summarized information from a variety of sources to

attain goals. In either case management action is based on information that isaccurate, complete, concise and timely. MIS has been successful in meeting

these information criteria quickly and responsibly. MIS is a person machine

system and a highly integrated grouping of information processing function

designed to provide management with a comprehensive picture of specific

information of specific operations. It is actually a combination of the

information systems.

Management information must be available early enough to affect a decision.

Operationally MIS should provide for file definition file management and updating

transaction and enquiry processing and one or more databases linked to an

organizational database.

A key element of MIS is the database- A not redundant correction of interrelated

data icons that can be processed through application, programs and available to


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many users. Sharing common data means that many programs can use the same

files or records. Information is accessed through a database management system

(DBMS).

The primary users of MIS are middle and top management, operational managers

and support staff. Middle and top management use MIS for preparing forecasts,

special request for analysis, long range plans and periodic reports. Operationalmanagers use MIS primarily for short range planning and periodic and exception

reports. The support staff finds MIS useful for the special analysis of information

and reports to help management in planning and control.

Decision Support System: - MIS provides limited support to top level management

for decision making. DSS advances the capabilities of MIS. It assists management

in making decisions.

Decision support system stands for

Decision- Infesises decision making in problem situation.

Support- Requires computer added decision situation enough structure to permit

computer support.

System- Combines the integrated nature of problem solving suggesting a combine

man , machine and decision involvement.


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DSS results from adding external data sources, accounting and statistical models

and interactive query capabilities. The outone is a system designed to serve all

levels of management and top level managements in particular with what if

unstructured problem situation.

Harvard Simon described decision making as a three phase continuous process,

model beginning with intelligence and moving forward decision and choice. The

process is invoked by the recognition of a problem. The resulting decision is then

directed at solving problems. The intelligence face of decision making involves the

awareness of a problem. It requires a closer look at the problem and thorough

evaluations of a variable and their relationship. A DSS can provide intelligence

through retrieval and statistical packages. The design face of decision making

focuses on the evaluation of decision alternative. During the space computer based

records or models may be used for decision design. The outputs of the model are

the basic for the choice face of decision making.


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Chapter-3

SYSTEM DEVELOPMENT LIFE CYCLE

Introduction

To understand system development we need to recognize that a candidate system has a life

cycle just like a living system or a new product. System analysis and design are keyed to

the system life cycle. The stages are shown in figure. The analyst must progress from one

stage to another methodically, answering key question and achieving results in each stage.

Recognition of need (initial investigation) -> feasibility studies-> analysis-> design->

program construction and testing-> implementation-> post implementation and

maintenance

1- Recognition of Need: - what is the problem? One must know what the problem isbefore it can be solved. The basis for a candidate system is recognition of the need

for improving an information system or a procedure. For example: - a supervisor

may want to investigate the system flow in purchasing or a bank president has been

getting complains about the long lines in the drive in. this need leads to a

preliminary survey or an initial investigation to determine whether an alternative

system can solve the problem.

2- Impetus for System Change: - The idea for change originates in the environmentor from within the firm. Environment based ideas originate from customers,

vendors, government sources and the like. For example: - new unemployment,

competitions, regulations may make it necessary to change the reporting processor

format and contents of various reports as well as file structure. Customers complain

about the delivery of the orders may prompt and investigation of the delivery


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schedule, the experience of truck drivers or the volume of orders to be delivered.

When investigated each of these ideas lead to a problem definition as a first step on

the system life cycle process.

Major Components of Change

3- Feasibility Studies: - Depending on the results of the initial investigation, thesurvey is expended to a more detailed feasibility is a test of a system proposal

according to its work ability, impact on the organization, ability to meet user needs

and affective use of resources, the objective of the feasibility study is not to solve

the problem but to acquire a sense of its scope. During the study, the problem

definition is crystallized and aspects of the problem to be included in the system are


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determined. Consequently, cost and benefits are estimated with greater accuracy at

this state. The result of the feasibility study is a formal proposal. This is simply a

report a formal document detailing the nature and scope of the proposed solution.

The proposal summarizes what is known and what is going to be done. It consists of

the following:

Statement of the Problem: - a carefully worded statement of the problem thatled to analysis.

Summary of Finding and Recommendation: - a list of the major findings andrecommendations of the study. It is ideal for the user who requires quick access

to the results of the analysis of the system under study.

Details of Finding: - an outline of the methods and procedures undertaken byexisting system followed by coverage of the objectives and procedures of the

candidate system.

Recommendation and Conclusion: - specific recommendation regarding thecandidate system, including personal assignments, cost, project schedule and

target dates. After the proposal is received by management, it becomes a formal

agreement that paves the way for actual design and implementation. This is a

crucial decision point in the life cycle.

4- Analysis: - Analysis is the detailed study of the various operations performed by thesystem and their relationships within an outside of the system. A key question is-

what must be done to solve the problem? One aspect of the analysis is defining the

boundaries of the system and determining whether or not a candidate system should

consider other related system. During analysis data are collected on the available

files, decision points and transaction ended by the present system. The tools used in

analysis are data flow diagrams, interviews, onside observations and questionnaires

are examples. The interview is a commonly used tool in analysis. It requires special

scales and sensitivity to the subjects being interviewed. Training experience and

commonsense are required for collection of the information needed to do the

analysis.


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Once analysis is completed, the analyst has a form understanding of what is to be

done. The next step is to decide how the problem might be solved. Thus in system

design we move from the logical to the physical aspects of the life cycle.

5- Design: - The most creative and challenging face of the system life cycle is systemdesign. The term design describes a final system and the process by which it is

developed. It refers to the technical specification that will be applied in

implementing the candidate system. It includes the construction of program and

program testing. The key question here is how the problem be solved.

The first step is to determine how the output is to be produced and in what format.

Samples of the output (& input) are also presented. The second is that the input data

and master files (database) have to be designed to meet the requirements of the

proposed output. The operational processing faces are handled through program

construction and testing, including a list of the program needed to meet the system

objectives and complete documentation. Finally details related to justification of the

system and an estimate of the impact of the candidate system on the user and the


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organization are documented and evaluated by management as a step toward

implementation.

The final report prior to the implementation face includes procedure flow chart,

record layouts, report layout and a workable plan for implementing the candidate

system. Information on personal, money, hardware, facilities and their estimated

cost must also be available. At this point projected cost must be close to actual cost

of implementation.

6- Implementation Face: -The implementation face is less creative than systemdesign. It is primarily concerned with user training side presentation and file

conversion. When the candidate system is linked to terminals or remote sides, the

telecommunication network can test of the network along with the system are also

included under implementation.

During the final testing, user acceptance is tested, followed by the user depending

on the nature of the system extensive user training may be required.

System testing checks the readiness and accuracy of system to access, update and

retrieve data from new lines. Once the program become available, test data are read

into the computer and process against the files proved by testing. If successful the

program is run with the live data. Otherwise a diagnostic processor is used to

locate and correct errors in the program.

7- Post Implementation and Maintenance: -After the implementation face iscompleted and the user staff is adjusted to the change created by the candidate

system, evaluation and maintenance begin. Like any system, there is an edging

process that requires periodic maintenance of hardware and software. If the new

information is inconsistent with the design specifications then changes have to be

made. Hardware also requires periodic maintenance to keep in tune with design

specification. The importance of maintenance is to continue to bring the new system

to standards.

User priority is changes in organizational requirement or environmental factor also

call for system enhancements.


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Needs Identification: - The success of system depends on large end of how accurately a

problem is defined, thoroughly investigated properly carried out through the choice of

solution. User need identification and analysis are concerned with what the user need.

The user or the analyst may identify the need for the candidate or for an enhancement in the

existing system. Shared, complete and accurate information requirements are essential in

building computer based information system. There are three key strategies or general

approaches for determining information regarding the users requirements: -

1- Asking2- Getting information from the existing information system3- Prototyping

Asking: - This strategy obtains information with users by simply asking them about the

requirements. It assumes a stable system where users are well informed and can overcome

basils defining their problems. There are three key asking methods: -

1- Questions may be open ended or closed. An open ended question allows respondentto formulate to response. It is used when the feelings or ideas are important. In

contrast a closed question request one answer from a specific set of responses. It is

used when factual responses are known.

2- Brainstorming: - it is a technique used for generating new ideas and obtaininggeneral information requirements.

3- Group consensus: - ask participants for their expectations regarding specificvariables.

Getting information from the existing information system: - Determining information

from an existing application has been called the data analysis approach. It simply asks the

user what information is correctly received and what other information is required. It

realized heavily on the user to articulate information needs. The analyst examines all

reports, discusses with the user each piece of information, examined and determines

unfulfilled information needs by interviewing the user. The analyst is primarily involved in

improving the existing flow of data to the user.


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Prototyping: - The third strategy for determining user information requirement is used

when the user cant establish information needs accurately before the information system is

built. The reason could be the lack of an existing model on which to base requirement or a

difficulty in visualizing candidate system. In this case, the user needs to anchor on real life

systems from which adjustment can be made. Therefore the iterative discovery approach

captures an initial set of information requirements and builds a system to meet these

requirements. As users gain experience in its use, they request additional requirements or

modifications in the system. In essence, information requirements are discovered by using

the system, prototyping is suitable in environment where it is difficult to formulate a

concrete model for defining information requirements and where the need of the user are

evolving.

Problem, definition and project initiation: - The first step in an initial investigation is to

define the problem that let to the user request. The problem must be slotted clearly,

understood and agreed upon by the user and the analyst. It must state the objectives the user

is trying to achieve and the results the user wants to see, emphasis should be on the logical

requirement what must be the results of the problems rather than the physical requirements.

Facts Gathering and Its Techniques

After performing the primary investigation the analyst begins to collect data on the existing

system output, input, and cost. The tools used in data collection are

1- Review of written document2- Onside observation3- Interviews4- Questionnaires5- Background reading Review of written document: - When available, all documentation on data carriers

(forms, records, reports, manuals etc.) is organized and evaluated. Included in

procedures manuals are the requirement of the system which helps in determining

to what extend they are met by the present system. Unfortunately, most manuals are

not up-to-date or may not be readable. Day-to-day problems may have forced


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which they are responding. In contrast the information obtained through a

questionnaire is limited to the written response of the subject to predefine question.

Background Reading: - Once the project is initiated, the analyst begins to learnabout the setting. The existing system and the physical processes related to the

revised system. For ex: - it is important to understand the structure of bank, who

runs it, who reports to safe deposit area, there relationship and accounting in

customer service and nature, frequency and level of interaction between the safe

deposit and these departments. Therefore the analyst should prepare an organization

chart with a list of the function and the people who perform them. In doing so,

he/she would have a better feel for the work environment in which safe deposit

operates the kinds of customers involved and the procedures employees following

conducting business in safe deposit.

Fact Analysis Phase

As data are collected, they must be organized and evaluated and conclusion drawn

for preparing a report to the user for the final review and approval. Many tools are

used for data organization and analysis. These tools are input/ output analysis,

decision tables and structured charts.

Input/output analysis identifies elements that are related to the input and output of agiven system. Flow charts and dataflow diagrams are excellent tools for

input/output analysis. Decision table describes the data flow within a system that is

generally used as a supplement when complex decision logic cant be represented

clearly in a flow chart. As a documented tool, they can provide a simpler form of

data analysis than the flow charts. When completed they are an easy to follow

communication device between the technical and non-technical personnel. They are

verbally oriented to managers, easy to learn and update and continue to function

once the logic is developed.

Structured Chart: - This is a working tool and an excellent way to keep track of the

data collected for a system.

Information Gathering: -


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Information gathering is an art and a science, the approach and manner, in which

information is gathered, requires persons with sensitivity, commonsense and

knowledge of what and when to gather and what channels to use in securing

information. Additionally the methodology and the tools for information gathering

require training and experience that the analyst is expected to have. This means that

information gathering is neither easy nor routine. Much preparation, experience,

training are required.

1- What kind of information do we need?Before one determines where to go for the information or what tools to use, the

first requirement is to figure out and what information to gather.

Policies Goal Objectives Organization structure to info. gathering

Auth. relationship job functions Info. requirement interpersonal relationship work flow

Method & procedures

Work schedules

Information about the firm/organization

Information about the organization policies, goals, objectives and structure explains

the kind of environment that promotes (or hinders) the introduction of computer

based system. Company policies are guidelines that determine the conduct of

business. Policies are translated into rules and procedures for achieving the goals. A

statement of goals describes management and commitment to objectives and

direction system development will follow.

After policies and goals are set, a firm is organized top meet these goals. Policies,

goals, objectives and structures are important elements for analysis.

The organization

User staff

The work itself


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Information about the user staff: -

Another kind of information for analysis is knowledge about the people to run the

present system, there job functions and information requirements, the relationship

of their jobs to the existing system and the interpersonal network that holds the user

group together. Information of this kind highlights the organization chart and

establishes a basis for determining the importance of the existing system for the

organization.

Information about the work flow: -

Work flow focuses on what happens to the data to various points to a system. This

can be shown by a data flow diagram or a system flowchart. A data flow diagram

represents the information generated at each processing points in a system and the

direction it takes from the source to the destination. In contrast the system flow

chart describes the physical system. The information available from charts explains

the procedure used for performing task and one should use.

Where does information originated: -

Information is gathered from two principle sources- personal or written documents

from within the organization and from the organization environment. The primary

external sources are: -

1- Vendors2- Government document3- Newspapers and professional journals.The primary internal journals are:

1- Financial2- Personal staff3- Professional staff

Information gathering tools:-

Interviewing: - Interviews are the formal meetings where the analyst can collect

information about the working of the present system and the requirement of any

planned replacement. It can be used for a variety of different purposes as:-

1- To collect information about the procedure taking place in an organization.


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2- To verify the analyst understanding of system operations with users of all levels.3- To confirm aspects of a purposed system design.4- To build confidence in the design of a new information.Advantages: -

1- The flexibility of interview makes it a superior technique for enquiring intoareas which are difficult to be explored using any other technique.

2- It provides a better opportunity then the questionnaires to evaluate the validityof the information collected. The interviewer can not only observe what subjects

but also study their body language and expression.

3- It is an affective technique for getting information about complex subjects andfor sensing the feelings underline opinions.

4- Generally people prefer being interviewed rather than filling up lengthyquestionnaires.

Disadvantages:-

There is one drawback which people from opting to this method of collecting

information. The drawback is the long preparation time that it takes. This method

requires more time and money for its conduction.

Planning and interview:-the three crucial aspects of the interview need to be plan by

the analyst. These aspects are:-

1- The object of the interview2- The time and the venue of the interview3- The authorization for the interviewConducting the interview:-

The analyst should start the interview by giving a clear explanation of the purpose

of the interview. The analyst should also specify by the subject first selected and

assure that the information collected during interview will be treated as

confidential.

Concluding the interview: - It is important to stick to the agreed time and conclude

the interview with a summary of the main discussion point.

Questionnaires: - In situation when it is not possible for the analyst (because of

time, distance or cost) to interview persons involved in a system. The questionnaire


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is considered as a tool for gathering required information. A questionnaire offers the

following advantages: -

1- It is easier to administer as compared to the interview as economical.2- A wide geographical area can be covered and a large number of people can be

contacted using this method.

3- The logical order of the question and the standardized instruction for givinganswers ensure uniformity of questions.

4- The respondents feel free to express themselves in questionnaires then in aninterview.

5- With questionnaire the respondent does not feel pressure of answering thequestion there and then. They get enough time to think about the question and

the response.

But questionnaires have the following disadvantage: -

The major disadvantage is a low percentage of return. Another disadvantage is that many

people are not good at writing.

Types of interviews and questionnaires:-

Interviews can be highly unstructured where neither the questions nor the respective

responses are specified in advance and highly unstructured in which the questions and

responses are predefined.

1- Unstructured approach: - the unstructured interview allows respondents to answerquestions at will in their own words. The responses are uninhibited rather than

forced. They are self and reveling and personal rather than general or superficial.

The analyst assumes the role of an interviewer who encourages the respondent to

speak without any hesitation and helps them to express their feelings and opinion.

This is best achieved when the subject are willing to share and have no feeling of

disapproval. However, this approach is more time consuming.

2- Structured approach: - in this, all subjects are asked the identical questions in a setorder. This is done to ensure that all subjects are answering identical questions

which include the reliability of the responses.


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3- Structured interviews and questionnaires may have questions of either closed oropen ended type. An open ended question is one which does not need a specific

response while a closed ended question is one in which the responses are given as a

set of options.


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Chapter-5

STRUCTURED SYSTEM ANALYSIS

Structured analysis is a set of techniques and graphical tools that allow the analyst to

develop a new kind of system specification that are easily understandable to the user. The

traditional approach focuses on the cost benefits and feasibility analysis, project

management, hardware and software selection and personal consideration. In contrast,structured analysis considers new goals and structured tools for analysis. The new goals

specify the following: -

1- Use graphics wherever possible to help communicate pattern with the user.2- Differentiate between logical and physical system.3- Build a logical system model to familiarize the user with system characteristic and

interrelationship before implementation. The structured tool focuses on the tools:

essentially the dataflow diagrams, data dictionary, structured English decision trees

and objective is to build a new document called system specification.

Tools for Structured System Analysis: -

1- Data flow diagrams:

A dataflow diagram depends on the four things:

1- Flow of data2- Data process3- Data stores4- Data source or sink

Data flow diagram:


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Dataflow diagramming is one of the structured analysis techniques. Dataflow diagram is

the diagrammatic representation of a system which provides a more complete clear and

global understanding of the system under investigation.

Dataflow diagram depicts the passage of data to a system. It is also known as a bubble

chart and aims at refining system requirements and identifying major transformations that

will become programs in system design. Dataflow diagrams are used to emphasize the

logical flow of data with the system. The basic symbol used is a circle or bubble and is

called transform since it identifies a function that transform data. The dataflow diagram

depicts the passage of data through a system by using four basic symbols.

These are:

1- Data flows

2- Data process3- Data stores4- Data source or sink

1- A rectangular box defines a source (or originator) or destination (sink) of a systemdata.

2- An arrow identifies data flow (data in motion). It is a pipeline through which the dataflows.

3- A circle or a bubble represents a process that transforms incoming dataflow intooutgoing data flow.

4- An open rectangle is a data store (data addressed or a temporary repository of data).Dataflow: - A dataflow is a root which enables packets of data to travel from one point to

another. The data may from a source to the process or to end from a data store or process.

An arrowed line shows the flow with the arrow head indicating the direction of flow.

Here the application form passes from the student (source) to a process which checks the

student details. The names given to the data flow must clearly describe them. Though it is

essential to name the data flows but data flows moving in and out of the stores do not

require names. The store names describe them.


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Process: - These represent transformation, changing incoming data flows into outgoing

dataflow. Process name must give an idea of what happens to the data as it passes through

the process.

Here the incoming flow (application form) to the process check details is transformed into

two outgoing flows. A valid registration form and a flow which indicates that the form

requires further clarification (query).

Data Stores: - Data store is a depository of data which is represented by an open rectangle.

Stores should also be assigned proper descriptive name. A store may be used in the

checking of data.

Here the process check details need access to data which allows checking. The data icons

require to properly carryout this process must be available in the store status details. The

arrow used in single headed and points toward the process. This indicates that the process

does not alter the contents of the store. It only uses the data available. If the contents of the

store are need as well as modified by the process, then the diagram uses a dot head arrow.

Data sources or sink: - A source or a sink is a person or part of an organization which

feeds or receives the data from the system but is considered to be outside the context of the

data flow model. A square defines a source or a sink which is build as the external to the

system under investigation.


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Developing DFDs

Context diagram of a book ordering system for a book store

The highest level view of a system, a context diagram is shown above. It gives an

overview of an organization system that depicts the system boundaries, external entities

and the system. The next step of the analysis is to examine the context diagrams for the

processors which are depicted by the single process. The final detail of the book ordering

system provides four detailed sub-processors:-

Types of DFDs:-

1- Physical DFDs2- Logical DFDsBoth types of DFDs support the top down approach for the system analysis.1- Physical DFDs: - Physical DFDs are implementation dependent. They are useful for

documenting the existing system to ensure that the analyst understand it properly.

Physical DFDs depict the flow of data and work through a system. The four symbols

that can appear in the DFDs are the process, the internal and external entity, the data

store and the data flow.


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These diagrams facilitate the analyst in sketching a comprehensive and complete

picture of the current system. It is easier for the analyst to start by depicting the

interaction between the physical components- people, document, form and equipment-

then to understand the policies that are used to manage the applications. Physical DFDs

are useful for communicating with users and provides a way to validate the users

current view of the system.

2- Logical DFDs: - A logical DFD is a tool for drawing a model of an informationsystems processing requirement. It is an implementation- independent view of a

system, concentrating on the flow of data between processors without giving any

consideration to the specific devices, storage location or people in the system. It

eliminates the specification on the physical characteristic listed in the physical DFDs.

Decision trees: - It is a graphical technique that shows a decision situation as a linked

series of nodes and branches. The two main components of the decision trees are: -

1- Decision points which are represented by nodes.2- Actions which are represents by ovals.

A decision tree is a diagram that resembles a tree, with a root on the left hand side and

branches representing each decision. It is read from left to right and the actions to be

undertaken are recorded down the right hand side of the diagram.

The root of the tree, on the left of the diagram is starting point of the decision sequence.

The particular branch to be followed depends on the prevalent conditions and decision to

be made. Progression from left to right along the particular branch is the result making a

series of decisions. Following each decision point is the next set of decision to be

considered. The nodes of the tree thus represent conditions and indicate that a

determination must be node about which condition exist before next path can be chosen.

The right side of the tree lists the action to be taken depending on the sequence of

conditions that is followed.

Developing a decision tree is beneficial to analyst as the need to describe condition and

action compels the analyst to formally identify the actual decision that must be taken.


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Decision table: - This is useful for representing the conditional logic of processes where

different actions are to be taken depending upon the occurrence of a particular combination

of conditions.

A decision table appears as a matrix of rows and columns that shows conditions and

corresponding actions. Decision rules, included in a decision table, states what procedure is

to follow when certain condition exist. This method has been used in analysis of business

functions such as investing control, sales analysis, credit analysis and transportation control

and routing. A decision table is divided into four sections:-

1- Stub2- Entries3- Action stub4- Action entriesThe condition stub identifies total set of relevant test or condition. These conditions require

yes or no answers. Combination of these conditions are then identified and expressed as

rules or conditions entries.

Condition entries provide all possible permutations of yes or no responses related to the

condition statement.

Action stub list the possible actions which can occur as a result of different condition

combinations.

Action entries show what specific action in the set to take when selected or group of

conditions are true.

Preparation of a limited entry decision table: -

1- Identify all condition and write them down in the condition stub with the most criticalone first.

C1: good payment history

C2: order value>5000

C3: association>10 years

2- Record all possible actions in the action stub. The sequence will be as they occurA1: priority treatment

A2: normal treatment


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3- The number of rules in a limited entry table can be calculated by using the formula 2 c.In our example three conditions produce 2

3rules, since each condition entry can be Y

or N.

4- Make the action entries:Condition stub Condition entry

C1: good pay history

C2: order value> 5000


Y Y Y Y N N N N

Y Y N N Y Y N N

Y N Y N Y N Y N

A1: priority treatment


* * * *

* * *

5- Check the table for completeness by counting the rules. In the limited entry table thereshould be 2

crules in total, where c is the number of rules given in the condition stub.

Decision table with consolidation: -

The last step involves checking the table for redundancy. This happens when two or

more rules exist with different combination of conditions leading to some action. In

such situation the rules where possible combinations should be consolidated. A

consolidation is indicated by a broken line which states that whether yes or no. theaction remains the same.

Condition stub Condition entry

C1: good pay history

C2: order value> 5000


Y Y Y Y N N N N

Y Y N N Y Y N N

- - Y N Y N - -

A1: priority treatment


* * * *

* * * *


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Decision trees with four consolidation

Structured English: - it is a tool for sharpening the narrative for described processing

logic and procedures. It is based on the principle of the structured programming. It is

created by the merging of the English language with the syntax of the structured

programming. It tries to express the verbal statement in the more logical form. The

structured English uses natural language along with the idea of logic and block structuring

used in a computer language.

Structured English uses standard narrative constructs that permit certain degree of user

understanding. Structured English specification still requires analyst to identify the

conditions that occur and alternative actions to be taken. No special symbols or formats are

used. Entire process can be stated quickly in English like statements.

COMPUTE DISCOUNT

Add up the number of copies per book title

IF: order is from bookstore.

AND IF order is of six copies or more per book title

THEN: discount is 25%.

ELSE (order is for less than six copies per book title.)

SO: no discount is allowed.

ELSE (order is from library or from individuals)

SO- IF order is for 50 or more copies per book title.


ELSE IF order is for 20 to 49 copies per book title.


ELSE IF order is 6 to 9 copies per title.


ELSE (order is less than 6 copies per book title).

THEN: discount is not allowed.


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Data dictionary: -

A data dictionary is a catalog- a repository- of the elements in the system. In other words it

is simply a record of data about data. In the data dictionary you will find the following

elements.

1- Data flows2- Data stores3- Processes

The data dictionary stored details and descriptions of these details.

A properly developed data dictionary provides answers to questions like how many

characters are in the data icon, by what other name it is referenced etc. data dictionary is

developed during data flow analysis and helps the analyst involved in determining system

requirements.

The reason why analyst use data dictionary mare as follows: -

1- To manage the details in the large system.2- To communicate a common meaning for all system elements.3- To document the features of the system.4- To facilitate analysis of details in order to evaluate characteristics and determine

where system changes should be made.

5- To find errors and omissions in the system. Components of a data dictionary: -

The dictionary contains two types of descriptions for the data flowing through the system-

data elements and data systems. Data elements are grouped together to make up a data

structure.

Data elements: - this is the item of data which cant be decomposed further. In other words

data elements are the fundamental building blocks of the system.

For ex: - invoice number, invoice data etc.

The data dictionary entry for the data elements consists of the following items: -

1- Name: - a meaningful unique name.2- Description: - a short description of what the data elements represent.3- Aliases: - additional names for the data elements.4- Length: - size of the element.


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5- Values: - it is the list of possible values for the data elements.For ex: - name: part - color

Description: - This is the color of the part of the machinery and is ordered time to time

from the local vender.

Alias: - P_color, color

Type- character

Length: - 15.

Data values: - may take one of the following values: -

Red, orange, yellow, blue.

The process and stages of system design

The process of design: - the design phase focuses on the detailed implementation of the

system recommended in the feasibility studies. Emphasis is on translating performance

specification into design specification. The design phase is a transition from a user oriented

document to a document oriented to the programmers or database personnel.

The information system design objectives are as follows: -

1- Support business activities2- Ensure that user requirements are met3- Provide ease of use4- Specify the logical design elements5- Provide software specification6- Confirm to design standard

The main objective of the system design is to deliver the requirements as specified

in the requirement specification document.

Logical and physical system design:

Information system provides solution to a business problem. It is in the design

phase that the user requirements finalized in the analysis space are translated into

practical based of achieving them. There are two levels of system design as follows:

1- Logical design2- Physical design


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Logical design: - In a logical design, a specification of the principal features of the new

system, which satisfies the systems objectives are produced by the designer. Logical

design results in the blueprint of the new system. So the part of the design process that is

independent of any specific hardware or soft ware platform is referred to as logical design.

It describes the input (forms, screens, dialogue boxes), outputs (reports, displays),

databases (data stores), procedures (data flows) - in a format that meets the users

requirements. When analyst develops the logical system design, he specifies the users

need at a level of detail that defines the information flow into and out of the system and the

required data resources. The various functions that are performed in the logical design

phase include

1- Reviewing the current physical system. Its data flows, file contents, volume, frequencyetc.

2- Preparing input specifications that are establishing the format contents and frequency ofreports, including terminal specification and location.

3- Preparing edit, security, control specifications. This entails specifying the rules forediting backup procedures and the controls that ensures processing and file integrating.

4- Specifying the implementation and plans.5- Preparing a logical design walkthrough- the information plan review.6- Reviewing benefits, cost target dates and system constraints.

After finding out the users requirement a system designer works to identifies data

requirements. The next step involves establishing the processing logic to generate the

desired outputs from the available inputs, this step involves data flow analysis and

processing logic analysis. Data flow analysis facilitates in arriving at a logical

organization of data into computer files. A file is a collection of identical records,

which in turn are collection of fields of information about a particular entity.

The structured system design tools that can be used to provide a logical representation

of data flow analysis and data processing analysis in a computer based information

system are 1- data dictionary 2- data flow diagrams 3- decision table 4- structured

English 5- decision trees


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Representation of logical and physical design

Design Methodologies: - for developing a system, logical methods must be defined more

clearly that needs user requirements. It has lead to new technologies and methodologies

that do the following functions: -

1- Improve productivity of analyst and programmers.2- Improve documentation and subsequent maintenance and enhancement.3- Reduced cost overruns and delays.4- Improve communication among the user, analyst, designer and programmer.5- Standardize the approach to analysis and design.6- Simplify design by segmentation.

Structured Design: - It is a data flow based methodology. The approach begins with a

system specification that identifies inputs, outputs and describes the functional aspects of

the system. The system specifications then are used as the basis for the graphic


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3- The couple is represented by an arrow with a circular tail. It represents data itemsmove from one module to another.

4- Here O, P and R are couples. Module A calls B, passing O downward. Likewisemodule A call C passing P downward and receiving one back.

In the functional decomposition approach to structured design is partitioned into smaller

modules so that each module is small enough to be manageable. In the evaluation of the

program two criteria are considered: -

1- The modules connection to other module is called coupling and its intermodule strength

or cohesion.

Module coupling refers to the number of connection between a calling and a called

module and the complexity of these connections there must be at least one connection

between a module and a calling module. Modules cohesion refers to the relationship

among elements within a module. If module does more than one discrete task, the

instruction in that module are said not be band together very closely. Modules that perform

only one task are said to be more cohesive (and less error prone) than the modules that

perform multiple task.

Forms driver methodology- the IPO charts: -

In structured design a hierarchy chart represents a good program design if it meets the

criteria of cohesion and coupling. Each modules performs a single function (cohesion) and

should be independent of the rest of the program (coupling). Each criteria call for more

details than are appearing. This prompts the analyst to develop input/process/output (IPO)

charts for each module in the hierarchy chart.

HIPO and IPO charts: -

HIPO is the forms driven technique. In this standard forms are used to document the

information. It consists of a hierarchy chart and an associated set of input/process/output

charts. HIPO captures the essence of top down decomposition. It describes the data input

and output from processes and defines the data flow composition. It was developed by

IBM. As a design aid and implementation technique with the following objectives: -

1- Provides a structure by which the function of a system can be understood.


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2- State the function to be performed by the programmer rather than specifying the

program statement to be used to perform the functions

3-Provide the visual description of input to be used and output to be produced for each

level of the diagram. HIPO makes the transformation of input to output data visible.

Author: . System/Program: . Date:. Page:of

Diagram ID:. Name:. Description:..

The information package format consists of the following: -

Visual table of contents shows the structures of the diagram and the relationship of thefunction in a hierarchical manner.

Overview diagram describes the major function and reference the detail diagramneeded to expend the functions adequately.

Detail diagram contains an extended description section that amplifies the process stepsand references the code associated with each process step.

3- Structured Walkthrough: - An activity of all phases of a structural project is the

walkthrough. It is an interchange of ideas among people who review a project presented by

its author and agree on the validity of a proposed solution to a problem. In a design

walkthrough the purpose is to anticipate as many problems in the design as possible. The

objective is to come up with a maintainable design that is flexible and adoptable and meets

the organization standard.

User Involvement: - Walkthrough may be held at various points in the SDLC. In addition

to system design they may be held to review the system test plan, program design and

production acceptance. In each case, the people who will be running the system should be

consulted.


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The probability of success improves with the users interest and involvement in the design

of the system. Promoting a users contribution in the walkthrough and throughput the

design phase can be crucial for successful implementation.

User implementation gives the designer implementation feedback as the design is been

completed. It also provides the user with a basic understanding of what the candidate

system will and will not do.

Input design: - Inaccurate input data are the most common cause of errors in data

processing. Errors entered by the data entry operators can be controlled by input design.

Input design is the process of converting user originated inputs to a computer based format.

In the system design phase, the expended data flow diagram identifies logical data flows,

data stores, sources and destinations. A system flow chart specifies master files (database)

transaction files and computer programs. Input data are collected and organized into groups

of similar data, once identified; appropriate input media are selected for processing.

1- Input data: - the goal of designing input data is to make data entry as easy, logicaland free from errors as possible. In entering data, operators need to know the

following: -

The allocated space for each field.Field sequence that must match that in the source document.

The format in which data fields are entered. For ex: - filling out the data field isrequired through the edited format mm/dd/yy.

When we approach input data design we design the source document that capture

the data and then select the media used to enter then into the computer.

Source document: - source data are captured initially on original paper or a source

document. Source document may be entered into a system from punch cards, from

disk or even directly through the keyboard. A source document may or may not

be retained in the candidate system. Thus each source document may be evaluated

in terms of: -

1- Its continue use in the candidate system.2- Extend of modification for the candidate system.


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3- Replacement by an alternative source document. A source document shouldbe logical and easy to understand. Each area in the form should be clearly

identified and should specify for the user what to write and where to write it.

Input media and devices: - source data are input into the system in a variety of ways. The

following media and devices are suitable for this operation: -

1- Punch cards: - These are either 80 or 90 columns wide. Data are arranged in asequential and logical order. Operators use a key punch to copy data from source

documents onto cards. This means that the source document and the card design

must be considered simultaneously.

2- Key-to-diskette: - This is modeled after the keypunch process. A disk replaces thecard and stores up to 325000 character of data- equivalent to data stored in 4050

cards like cards data on disk are stored in sequence and in batches. The approach to

source document and disk design to that of a punch card. Data must be in sequence

and logical cohesion.

3- MICR: - Magnetic Ink Character Recognizer translates the special fonts printed inmagnetic ink into the direct computer input.

4- MSR: - Mark Sensing Reader automatically converts pencil marks in apredetermined location on a card to punch holes on the same card.

5- OCR: - Optical Character Readers are similar to MICR readers except that theyrecognize pencil, ink or characters by that configuration (shape) rather than their

magnetic pattern. They are often used in remote locations free standing input

repletion devices or direct input media to the system.

6- OBR: - Optical Barcode Reader detects combination of marks that represent data.The most widely known system is the Universal Product Code (UPC), which code

retails items in stores.

7- CRT: - Cathode Ray Tube screens are used for online data entry. CRT screendisplays 20, 40 or 80 characters simultaneously on a television like screens. They

show as many as 24 lines of data.

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