SAD-Types Of System

There are mainly three types of system.

1.Physical or Abstract
2.Open or Closed
3.Man Made Information System


Physical systems are tangible entities that may be static or dynamic in operation. For example:-the physical parts of the computer center are the offices,desks,and chairs that facilitate operation of the computer. They can be seen and counted, they are static.

In contrast a programmed computer is a dynamic system. Data, programs, output are examples for dynamic system.

Abstract systems are conceptual or nonphysical entities.ex:-formulas of relationships among sets of variables.

System models

Model is a representation of a real or a planned system. The major system models are

1.Schematic models
2.Flow system models
3.Static system models
4.Dynamic system models

Schematic: A schematic model is two dimensional chat depicting system elements and their linkages.

Flow system: A flow system model shows the flow of the material,energy,and information that hold the system together. i.e it specifies the flow of logic in models. A widely used example is PERT (program evaluation and review technique).It is used to abstract a real world system in model form, manipulate specific values to determine the critical path, interpret the relationships and relay them back as a control.

Static system: This type of model exhibits one pair of relationships such as activity-time or cost-quantity. A widely used example is Gantt chart. This chart gives a static picture of an activity –time relationship.

Dynamic system: Dynamic systems are constantly changing system.ex:- business organizations are dynamic systems. A dynamic model approximates the type of organization or applications that analysts deal with.


This classification of systems is based on their degree of independence.

An open system has many interfaces with its environment. It permits interaction across its boundary. It receives inputs from and delivers outputs to the outside.ex:- for open system is an information system because it must adapt to the changing demands of the user.

A closed system is isolated from environment influences. A completely closed system is rare.


Information system reduces the uncertainty about a state or event. It is the basis for the interaction between user and analyst. It provides the informations like instructions commands and feedback. It determines the nature of the relationships among decision makers.

Information system can be defined as a set of devices, procedures and operating systems designed around user-based criteria to produce information and communicate it to the user for planning control and performance.

There are three major classifications for information system.
1. Formal information system
2. Informal information system
3. Computer based information system

Formal information system

A formal information system is based on the organization represented by the organization chart. The chart is a map of positions and their authority relationships, indicated by boxes and connected by straight lines. It is concerned with the pattern of authority, communucation and workflow. Informations are formally disseminated in instructions, memos or reports from top management to the intended user in the organization.

There are three categories of formal information system
1.strategic information system
2.managerial information system
3.operational information system

Strategic information system relates to long range planning polices. These are the direct interest of the upper management. Polices are the generalization that specify what an organization is going to do.ex:- financial investment in a company, human resources etc.

Managerial information system relates to short and intermediate range planning polices.

This is done by the direct interest of middle management and department heads for implementation and control. The duration will take several months to year.

Operational information system relates to short term polices. This deals with day-to-day activities like daily employee absence sheets, purchase orders, current stock available for sale.



It is an employee based system designed to meet personal and vocational needs and to help and solve work related problems. It also funnels information upward through indirect channels. It is a useful system because it works within the framework of the business and its stated policies.


A third class of information system relies on the computer for handling business applications. The computer is now a required source of information. System analysis relies heavily on computers for problem solving. This suggests that the analyst must be familiar with computer technology and have experience in handling people in an organization context.

Management information system (MIS):-

The computer has had a significant impact on the techniques used by management to operate a 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 control decisions.

Higher level management, for whom 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 is accurate, relevant, complete, concise and timely.MIS has been successful in meeting these information criteria quickly and responsively.

MIS is a person machine system and a highly integrated grouping of information  processing functions designed to provide management with a comprehensive picture of Specific operations. It is actually a combination of information systems to do the job, it  should operate in real time, handling inquiries as quickly as they are received.  Management information must also be available early enough to affect a decision.  
Operationally , MIS should provide for file definition, file maintenance and  updating, transaction and inquiry processing and one or more database linked to an  organizational database. Within an MIS a single transaction can simultaneously update all  related data files in the system. In doing so , we can reduce data duplication.

A key element of MIS is the data base- a nonredundant collection of interrelated data  Items that can be processed through application programs and available to many users.  All records must be related in some way. Sharing common data means that many  programs can use the same files or records. Information is accessed through a data base  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  requests for analysis,long range plans and periodic reports. Operational managers use  MIS primarily for short range planning and periodic and exception reports. The support  staff finds MIS useful for special analysis of information and reports to help  management in planning and control.

A major problem encountered in MIS design is obtaining the acceptance and support  of those who will interface with the system.

Decision support system (DSS):-

DSS advances the capabilities of MIS. It assists management in decision making. It is actually a continually evolving model that relies heavily on operations research.

Decision- emphasizes decision making in problem situations, not information processing, retrieval, or reporting.

Support:-requires computer-aided decision situations with enough structure to permit computer support

System:- accentuates the integrated nature of problem solving, suggesting a combined “man”, machine and decision environment

There are authors today who view DSS as an extension of MIS,DSS as independent of  MIS, or MIS as a subset of DSS.The commonly accepted view in the literature views  DSS as a second generation MIS.MIS is generated when we add predefined managerial  reports that are spun out of the transcation processing,report generation and online  inquiry capabilities-all integrated with a given functional area such as production MIS or  personnel MIS. DSS results from adding external data sources,accounting and statistical  models and interactive query capabilities. The outcome is a system designed to serve all  levels of management and top management in particular,in dealing with the “what if”  unstructured problem situations. It is a system with intrinsic capability to support ad hoc data analysis as well as decision-modeling activities.
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