1system concepts

8/3/2019 1System Concepts

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Structured System Analysis & Design


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SystemThe term system is derived from the Greek word systema, whichmeans an organized relationship among functioning units orcomponents.

A System is an orderly grouping of interdependentcomponents linked together according to a plan toachieve a specific objective.


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Interdependence: Interdependence means that parts of the

organization or system depend on one another. They arecoordinated and linked together according to a plan. Nosubsystem work in isolation. One subsystem depends on the inputof another subsystem for proper functioning, that is, the output ofthe one system is required input for another.

Integration: Integration is concerned with how a system is tiedtogether. It means that parts of the system work together withinthe system even though each part performs a unique function.

Central objective: The last characteristic of a system is that itworks toward a central objective.



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Elements of a System

There are following basic elements in systems analysis. Briefdescription of each element has been given below:

Inputs: Inputs are the elements (material, human resources,information) that enter the system for processing.The essentialelements of inputs are:

i) Accuracy: If the data is not accurate, the output will be wrong.ii) Timeliness: If data is not obtained in time, the entire systemfalls into delay.

iii) Proper format: The input must be available in proper format.

Outputs: First of all, we must determine what the objectives orgoals are; in other words, what is the main aim behind the system.Defining aim is very vital in system work. Output is the outcomeof processing.



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Process:The process is the element of a system that involves theactual transformation of the input into output. It is a logical set ofinstructions.

Control: The control element guides the system. It is the decisionmaking subsystem that controls the pattern of activities governinginput, processing and output.

Feedback: Control in a dynamic system is achieved by feedback.Feedback measures output against a standard that includescommunication and control.

Environment:The environment is the suprasystem withinwhich an organization operates. It is the source of external

elements that affects the system. In fact, it often determines how asystem must function.

Boundaries and Interfaces:A system should be defined byits boundaries the limits that identify its components, processes,and interrelationships when it interfaces with another system.



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Types of Systems

Systems have been classified in many ways. Commonclassifications are:-

Physical or Abstract System:

- Physical systems are tangible entities that may be static or

dynamic in operation.For example, the physical parts of thecomputer centre are the offices, desks and chairs that facilitateoperation of the computer. They can be seen and counted; they arestatic. In contrast, a programmed computer is a dynamic system.Data, programs output and application changes as the usersdemands or the priority changes.

- Abstract systems are conceptual or nonphysical entities. Theymay be as straightforward as formulas of relationship among setsof variables or models the abstract conceptualization of physicalsystem. A model is a representation of a real or a planned system.



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System ModelsThe analyst begins by creating a model of the reality (facts,relationships, procedures etc.) with which the system isconcerned. The major models are as follows:

Schematic Model: -

A schematic model is a two-dimensional chart depictingsystem elements and their linkages.

Flow system Model: -

A flow system model shows the flow of the material, energyand the information that hold the system together. There isan orderly flow of logic in such models.



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

Dynamic Model: -

A dynamic model approximates the type of organization orapplications that the analysts deal with. It depicts anongoing, constantly changing system. It consists of (1)inputs that enter the system, (2) the processor through

which transformation takes place, (3) the program(s)required for processing, and (4) the output(s) that resultfrom processing.



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Open or Closed Systems: An open system continually interacts withits environments. It receives inputs from and delivers output to theoutside. In contrast, a closed system is isolated from environmentalinfluences. In reality completely closed system are rare.

Five important characteristics of open systems are as follows:

a) Input from outside: Open system receives inputs from outside.

b) Entropy: All dynamic systems tend to run down over time, resulting inentropy or loss of energy.

c) Process, output and cycles: Open systems produce useful output andoperate in cycles, following a continuous flow path.

d) Differentiation: Open systems have a tendency toward an increasingspecialization of functions and a greater differentiation of theircomponents.

e) Equifinality: The term implies that goals are achieved through differingcourses of action and a variety of paths.



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Deterministic or Probabilistic Systems:

A deterministic system is one in which the occurrence of all eventsin perfectly predictable. If we get description of the system state aparticular time the next state can be easily predicted. An exampleof such a system is numerically controlled machine tool.

Probabilistic system is one in which the occurrence of events

cannot be perfectly predicted. An example of such a system is awarehouse and its contents.

Man- made Information Systems: It is generally believed thatinformation reduces uncertainty about a state or event. For

example, information that the wind is calm reduces the uncertaintythat a trip by boat will be enjoyable. An information system is thebasis for interaction between the users and the analyst. Itdetermines the nature relationship among decision makers. In fact,it may be viewed as decision centre for personnel at all levels.



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Information Systems

An information system may be defined as a set of devices,procedures and execution plan designed around user-based criteriato produce information and communicate it to the user forplanning, control and performance.

Computer Based information Systems depends mainly on thecomputer for handling business applications. They are classifiedas:

Transaction Processing Systems (TPS)

Management Information System (MIS)

Decision Support System (DSS)

Office Automation System (OAS)



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Transaction Processing System:

A transaction processing system can be defined as a computer based systemthat captures, classifies, stores, maintains, updates and retrieves transactiondata for record keeping and for input to other types of CBIS. TransactionProcessing Systems are aimed at improving the routine business activities onwhich all organization depend. A transaction is any event or activity thateffects the whole organization. Placing orders, billing customers, hiring ofemployees and depositing cheques are some of the common transactions.

Management Information System:

Earlier most of the computer applications were concerned with recordkeeping and the automation of routine clerical process. However, in recentyears, increasing attention has been focused on computer applicationproviding information for policy making, management planning and controlpurposes. MIS are more concerned with management function. MIS can bedescribed as information system that can provide all level of managementwith information essential to the running of smooth business. Thisinformation must be relevant, timely, accurate, complete and concise as iseconomically feasible.



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Decision Support Systems:

Decision support system assist managers who must make decisions that are nothighly structured, often called unstructured or semi-structured decision. Adecision is considered unstructured if there are no clear procedures for making thedecision and if not all the factors to be considered in the decision can be readilyidentified in advance. Judgment of the manager plays a vital role in decisionmaking where the problem is not structured. The decision support system support,does not replace, judgment of manager.

Office Automation Systems:

Office automation systems are among the newest and most rapidly expandingcomputer based information systems. They are being developed with the hopesand expectations that they will increase the efficiency and productivity of officeworkers - typists, secretaries, administrative assistants, staff professionals,managers and the like. Many organizations have taken the first step toward

automating their offices. Often this step involves the use of word processingequipment to facilitate the typing, storing, revising and printing of textual material.Another development is a computer based communication system such aselectronic mail which allows people to communicate in an electronic mode throughcomputer terminals. An office automation system can be described as a multi-function, integrated computer based system that allows many office activities to beperformed in an electronic mode.


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