System Analysis & Design - I

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System Analysis & Design- I, SAD, System, Characteristics

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System Analysis & Design - I

  1. 1. SYSTEM ANALYSIS & DESIGN - 1 Gagan Deep Rozy Computech Services 3rd Gate, K.U., Kurukshetra-136119 rozygag@yahoo.com
  2. 2. THE SYSTEM CONCEPT The term “system” is used in many different ways. Everyone is familiar with such expressions as “Professor Rajneesh has an impossible grading system” or “Deepak has a system for betting on the horses.” But for computer users, a system is a group of parts that are integrated for the purpose of achieving some objective. The following three characteristics are key: • A group of parts : A system has more then one element. A steering wheel is not a system, but it’s a vital part of a familiar system called an automobile. • Integrated parts : A logical relationship must exist between the parts of a system. Mechanical and electronic system, such as washing machines and video games, have many components that work together. • A common purpose of achieving some objective : The system is designed to accomplish one or more goals. All system elements should be tied together and controlled so that the system goal is achieved. Since a computer is a group of integrated parts that have the common purpose of performing the operations called for in the program being executed, it qualifies as a system. Gagan Deep, RCS, 3rd Gate, K.U.K., rozygag@yahoo.com
  3. 3. • 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 interdependent components linked together according to a plan to achieve a specific objective. The word component may refer to physical parts, managerial steps or a subsystem in a multi-level structure. • In our daily life, the word “System” comes across many a times but rarely the word is understood in its fullest sense. Almost every one of us have heard about Systems such as Education System, Economic System, Office System, Solar System, but what do they imply in the real sense is a main question. Gagan Deep, RCS, 3rd Gate, K.U.K., rozygag@yahoo.com
  4. 4. • Systems could be man-made such as education system, office systems etc., or a natural system such as solar system. • We would be dealing with man-made systems. These man-made systems have certain inputs which are processed and the result is certain outputs. • In education system, the main input is new students where they undergo the process of education and the output is a educated student. • We can also define a system where elements interacts with each other, responding to certain inputs to produce outputs as shown in figure 1. Gagan Deep, RCS, 3rd Gate, K.U.K., rozygag@yahoo.com
  5. 5. • As the definition goes each system has certain interacting elements. These elements interact with each other in a certain way so as to produce the required output from the given inputs. As we are dealing with man-made systems, so it is man who decides about what should be the inputs for a particular system and in what way different elements should react with each other to produce the desired output. This particular man who analyse (new and existing) and design or redesign the system is called System Analyst. Gagan Deep, RCS, 3rd Gate, K.U.K., rozygag@yahoo.com System Inputs Outputs
  6. 6. • The concept of systems would impose upon the System Analyst to look at the system as a whole. For example A Company Managing Director asking the Production Manager to study the present production system of the Automobiles Unit and to suggest improvements. The production system being so large, it can not be analysed by a single person, so, the system is divided into sub- systems. These sub-systems could themselves be again divided into sub-systems and so on till the level where input and output could be defined as shown in figure 2. Gagan Deep, RCS, 3rd Gate, K.U.K., rozygag@yahoo.com
  7. 7. • In our example where Production Manager could not analyse the system as a whole so he entrusted the work to the Assistant Production Managers of Production Unit who in turn entrust the work to Supervisors of the Unit. Finally the Production System was analysed at Supervisors level where all inputs and process of Production System were discussed to meet the new objective and the report submitted back to Production Manager who in turn reports to Managing Director. • Similarly system analyst also divides his system into sub-systems so that it becomes easier for him to go into the details of the whole system. Gagan Deep, RCS, 3rd Gate, K.U.K., rozygag@yahoo.com
  8. 8. TYPE OF SYSTEMS DETERMINISTIC AND PROBABILISTIC SYSTEM • In some of the systems the output or occurrences of all events are perfectly predictable, but in some of the systems the output or occurrences of events cannot be always perfectly predictable Those systems where one can predict the occurrence of events perfectly are called as deterministic systems and those systems where the events cannot be perfectly predictable are called probabilistic systems. • Example of a deterministic system could be a production system where the production unit that is a automobile production unit which produce 3 scooters in one hour, so the output after 8 hours could be perfectly predicted i.e. it would be 24 scooters. Example of a probabilistic system could be the closing balance of cash in an airlines reservation office on a given day. Unfortunately, it is the probabilistic system that the system analyst deals mostly with. Gagan Deep, RCS, 3rd Gate, K.U.K., rozygag@yahoo.com
  9. 9. CLOSED AND OPEN SYSTEM • These type of systems is based on their degree of independence. A closed system is one which is self- contained, that it does not interact with its environment. But in reality no system can keep itself isolated from its environment for a long time. It controls its input and environmental disturbance is minimum. Changing environment does not affect on closed system. • A open system has many interfaces with its environment. It does interact with its boundary. If the educational system in a country is such that it is directly related to the job requirements of the country, then we call such an educational system as an open system.. Gagan Deep, RCS, 3rd Gate, K.U.K., rozygag@yahoo.com
  10. 10. There are five important characteristics of open system: • Inputs from outside : Open systems are self-adjusting and self-regulating. • Entropy : All dynamic systems tend to run down over time, resulting in entropy or loss of energy. Open systems resist entropy by seeking new inputs or modifying the processes to return to a steady state. • Process, Output and Cycles : Open systems produce useful output and operate in cycles, following a continuous flow of path • Differentiation : Open systems can differentiate between its components and can perform specialised functions. • Equifinality : Most of the systems like to achieve their goals no matter what they choose. This form of achieving goals through different course of actions is another characteristic of open systems and we call this as equifinality Gagan Deep, RCS, 3rd Gate, K.U.K., rozygag@yahoo.com
  11. 11. STABLE SYSTEMS • In stable systems, there are well defined relationship between the various components but if these relationships have external disturbances then they are capable of returning to their desired state. The stability is measured in terms of certain elements remaining within previously set limits. For example, in an Inventory Control System, the Reorder Level of particular items is based on demand forecasts and past experiences. We can call a Inventory Control System as negative feed back mechanism wherein we record the things when they are deviating from limits. When the system has several such feed back loops whereby, if one loop is out of control another is activated to restore control, it is known as an ultra-stable system. Gagan Deep, RCS, 3rd Gate, K.U.K., rozygag@yahoo.com
  12. 12. CHARACTERISTICS OF SYSTEM The basic characteristics of system are • Organization • Interaction • Interdependence • Integration • Central objective Gagan Deep, RCS, 3rd Gate, K.U.K., rozygag@yahoo.com
  13. 13. Organization : Organization implies structure and order. It is the arrangement of components that helps to achieve certain objectives. For example, in a business system the hierarchical relationships starting with the Managing Director on top and leading downward to the workers represents the organization structure. Such an arrangement portrays a system subsystem relationship. Similarly computer system is designed around an input device, a central processing unit, an output device, and one or more storage units: When linked together they work as a whole system for producing information. The traditional principles on which organizations have been structured aim to achieve parity of authority and responsibility. • Harmony of objectives (all staff working to a common end). • Unity of command (each person having only one immediate superior). • Unit of direction (one manager and one plan for each major objective or set of objectives). Gagan Deep, RCS, 3rd Gate, K.U.K., rozygag@yahoo.com
  14. 14. Interaction : Interaction refers to the manner in which each component functions with other components of the system. In a business system, for example, purchasing must interact with production, advertising with sales, and payroll with personnel. • In a computer system, the central processing unit must interact with input devices to solve a problem. The interrelationship between various components of computer system enables it to perform. In an education system a teacher interacts with a student to disseminate knowledge or ideas of a particular subject. Gagan Deep, RCS, 3rd Gate, K.U.K., rozygag@yahoo.com
  15. 15. Interdependence : Interdependence means that parts of the organization or computer system depend upon each other. They are coordinated and linked together according to a plan. For example, in an education system:- a student is dependent on teacher to guide him/her and a teacher in turn is dependent on student where teacher expects student to respond him/her favourably and positively. In addition, the output of one sub-system may act as an input to another subsystem. Interdependence is further illustrated by the activities and support of system analysts, programmers and the operating staff in a computer centre. A decision to computerize an application is initiated by the use, analysed and designed by the analyst, programmed and tested by the programmer, and run by the computer operator. Gagan Deep, RCS, 3rd Gate, K.U.K., rozygag@yahoo.com
  16. 16. Integration : Integration refers to the holism of system. 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 system work together within the system even though each part performs a unique function. Successful Integration will typically produce a greater, clearer and total impact than each component works separately. Central Objective : The last characteristic of a system is its central objective. Objectives may be real or stated. Although stated objective may be the real objective, it is not uncommon for an organization to state one objective and operate to achieve another. The user should be aware of the central objectives of a computer application early in the analysis for a successful design and conversion. The analyst must work around such obstacles to identify the real objective of the proposed change. Gagan Deep, RCS, 3rd Gate, K.U.K., rozygag@yahoo.com
  17. 17. CONTROL MECHANISM • A system is not as simple as definition describes. We presuppose that output generated by the system is always according to the specifications. Suppose a computer program generating a output report might give the output but not according to desired specifications. A feed back is sought to check what went wrong in our specification. After we receive the feed back we correct the program and again run the program to get the report. Here data was the input, computer was a process and report was the output. In fact what has been introduced in the system is a control mechanism. For any system to be stable, a control mechanism is always necessary. Whenever the output of a system deviates from the limits which has been set, a control mechanism is required either to adjust the process or the inputs. Forces of control mechanism may not be able to adjust the inputs or processes in a way so as to bring output within the limits specified. In that case the output itself has to be adjusted. Gagan Deep, RCS, 3rd Gate, K.U.K., rozygag@yahoo.com
  18. 18. • One can know about the deviation has occurred in the outputs by seeing the feedback where the generated outputs are compared with standard outputs. Figure 3 below shows how controls in system would work • Every system which gets out of control, there must be a way of restoring controls. Therefore, there should be a control mechanism for each possible state of the system. The primary task of the system analyst is to analyse and design a system which is absolutely new or make a existing system more effective by modifications or by substantial redesign. The system involved could be economic, political, social institution such as business houses, government agencies, colleges and universities and usually a computer could be considered as an aid for improving the systems operation. System analyst may be responsible for system analysis, detail design of the computer system and outlining system specification. Gagan Deep, RCS, 3rd Gate, K.U.K., rozygag@yahoo.com
  19. 19. SYSTEM ANALYST The system analyst has two primary objectives • Assessment objective • Assistance objective Assessment objective : A system analyst has to observe, understand and evaluate the interactions which routinely occurs as a part of the Job under investigation. Herein the analyst has to know. • What is being done ? • Who is doing it ? • Why is it being done ? • How is it being done ? • What are major problems in doing it ? After the completion of assessment objective, the system analyst offers specific suggestions for improving the efficiency of Job under consideration. He does so by providing assistance. Gagan Deep, RCS, 3rd Gate, K.U.K., rozygag@yahoo.com
  20. 20. Assistance Objective : A system analyst is to provide alternative solutions to make the existing system more efficient. For this job, he seeks the help of the computer. At such times he acts like a communication-link between technology and user. Analyst now finds out other ways to deal with the existing problem and also checks the benefits and liabilities associated with these alternative approaches. • Better assessment of problems will provide better assistance, and probably the presence of other kinds of assistance gives the analyst a broader perspective for the assessment. • A system analyst must have good communication with all the people affected. Communication skill of system analyst should be sharp as he depends on others for both information and co-operation. System analyst in facts as an agent of change. Gagan Deep, RCS, 3rd Gate, K.U.K., rozygag@yahoo.com
  21. 21. Thanks! Dear Users I am writing and preparing these slides for you but not hearing anything from your side. If you want more slides please give me comments, they will work like a control mechanism and I will try to do the work as per your requirements. Regards Gagan Deep Rozy Computech Services 3rd Gate, K.U., Kurukshetra -136119 rozygag@yahoo.com Gagan Deep, RCS, 3rd Gate, K.U.K., rozygag@yahoo.com

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