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Process of design
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Process of design

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  • 1. Process of Design By:-Bharat Razdan Diksha Goel Bsc IT (IV)
  • 2. PROCESS OF DESIGN The design phase focuses on the detailed implementations of the system recommended in the feasibility study. The design phase is a transition from a user-oriented document to a document oriented to the programmers or data base personnel.
  • 3. System design goes through twophases of development Logical Design Physical Design
  • 4. Logical Design A data flow diagrams shows the logical flow of system and defines the boundaries of the system. For a candidate system it describes the inputs(source), outputs(destination), data bases(data stores), and procedures(data flow) all in a format that meet the users requirements. When analysts prepare the logical system design they specify the user needs at a level of detail that virtually determines the information flow into and out of the system and the required data resources.
  • 5. Physical Design This produces the working system by defining the design specifications that tell programmers exactly what the candidate system must do. In turn , the programmer writes the necessary programs or modifies the software package that accepts input from the user, performs the necessary calculations through the existing or data base , produces the report on the hard copy or display it on the screen and maintains an updated data base at all times.
  • 6. Contd.. Physical system design consists of the following steps: ◦ Design the physical system.  Specify input/output media.  Design the database and specify backup procedures. ◦ Plan system implementation. ◦ Devise a test and implementation plan and specify any new hardware /software. ◦ Update benefits, costs , conversion date , and system constraints(legal , financial , hardware , etc).
  • 7. Structured Design Structured design is a data-flow-based methodology . The approach begins with a system specifications that identifies inputs and outputs and describes the functional aspects of the system. From the DFD, the next step is the definition of the modules and their relationships to one another in a form called a structure chart, using a data dictionary and other structured tools.
  • 8. The Structured DesignMethod Structured English System Data Decision Specifications DFD Dictionary tree Decision table
  • 9.  Structured design is an attempt to minimize complexity and make a problem manageable by subdividing it into smaller segments, which is called modularization or decomposition. A design is said to be top-down if it consists of a hierarchy of modules, with each module having a single entry and a single exit subroutine.
  • 10. The advantage of this design areas follows:- ◦ Critical interfaces are tested first. ◦ Early versions of the design, though incomplete, are useful enough to resemble the real system. ◦ Structuring the design , provides control and improves morale. ◦ The procedural characteristics define the order that determines processing.
  • 11. Functional Decomposition It is a graphic tool for representing hierarchy . It has three elements:- The module is represented by a rectangle with a name. It is a contiguous set of statements. The connection is represented by a vector linking two modules. It usually means one module has called another module. The couple is represented by an arrow with a circular tail. It represents data items moved from one module to another.
  • 12. Module A The module is represented with a name. A B CThe connection is represented by a vector linking two modules. It usually means one module has called another module
  • 13. Coupling A B CThe couple is represented by an arrow with a circular tale. It represents data items moved from one module to another .In the figure O,P,Q are couples . Module A calls B passing OdownwardLike wise module A calls C, passing P downward and receiving Qback.
  • 14. Structured Walkthrough Structured walkthrough is an interchange of ideas among peers who review a product presented by its authors . The purpose is to anticipate as many problems in the design as possible. It is cheaper to make changes now than later during conversation. This is a practical implementation of “ A stitch in time saves nine”
  • 15. User Involvement Walkthroughs may be held at various points in the system development life cycle. They are held to review the system test plan, program design, and production acceptance. Promoting a user‟s contribution in the walkthrough and throughout the design phase can be crucial for successful implementation. It also bridges the gap between the designer, who as a staff person has an expert perspective , and the user with a generalist or managerial view.
  • 16. QUIZQ)How do we design physical system?a) Specify I/P, O/P media-> design database-> design physical information flow-> design physical design walkthroughb) design database-> Specify I/P, O/P media-> design physical information flow-> design physical design walkthroughc) design database-> design physical information flow-> design physical design walkthrough -> Specify I/P, O/P mediad) design physical information flow-> design physical design walkthrough -> Specify I/P, O/P media-> design database
  • 17. Q)System specifications‟ are formulated in which designing phase?a) Physical designb) Logical designc) Structure designd) None of the above
  • 18. Q)„Procedure specifications‟ are formulated in which designing phase?a) Logical designb) Structure designc) Physical designd) Feasibility design
  • 19. Q)What is the purpose of structured design?a) To increase reproducibility.b) To increase repeatability.c) For documentation purpose.d) To minimize complexity of problem.
  • 20. Q)What is not a development activity in structured design?a) Database designb) Implementation planningc) User documentationd) Feasibility study
  • 21. Q) The process of interchanging ideas among peers when reviewing a product is known asa) Couplingb) Structured Walkthroughc) Logical Designd) Physical Design