Program analysis and design, , wixom, and M. Roth © 2015 John Wiley & Sons, Inc. All rights 1Learning ObjectivesBe able to revise logical DFDs into physical DFDsBe able to create a structure chartBe able to write a program specificationBe able to write instructions using pseudocodeBecome familiar with event-driven programming © 2015 John Wiley & Sons, Inc. All rights 2Moving from Logical to ModelsMaking implementation decisions. © 2015 John Wiley & Sons, Inc. All rights 3The Physical Process ModelShow the implementation details and explain how the system will work, including.◦ Actual, specific technology.◦ Format of information.◦ Human interaction with system. © 2015 John Wiley & Sons, Inc. All rights 4The Physical DFDContains the same components as the logical same rules pertaining to balance additional details describing how the be built. © 2015 John Wiley & Sons, Inc. All rights 5Steps to Create the Physical DFDAdd implementation a human-machine system-related data stores, data flows data elements in the data the metadata in the CASE repository © 2015 John Wiley & Sons, Inc. All rights 6Contrasting a Logical and DFD Physical dfd. © 2015 John Wiley & Sons, Inc. All rights 7Designing Programs. © 2015 John Wiley & Sons, Inc. All rights 8Key DefinitionsProgram design - creating instructions for the top-down, modular approach - begin with the “big picture” and gradually add design document – all structure charts and specifications needed to implement the systemThe Structure ChartImportant program design all components of code in a hierarchical format. ◦ Sequence. ◦ Selection. ◦ the organization and interactions of the different program modules. © 2015 John Wiley & Sons, Inc. All rights . © 2015 John Wiley & Sons, Inc. All rights 11Structure Chart Elements Module Conditional Line. P. e. g. a. O. f. f. . Calculate. Current GPA. Library Module. On. Control Couple page. . Get Student. Grade Record. Data Couple. Loop. © 2015 John Wiley & Sons, Inc. All rights 12Building the Structure ChartProcesses in the DFD tend to represent one the structure chart.◦ Afferent processes – provide inputs to system.◦ Central processes – perform critical system operations.◦ Efferent processes – handle system outputsThe DFD leveling can correspond to the hierarchy © 2015 John Wiley & Sons, Inc. All rights 13Types of Structure ChartsTransaction structure – control module calls subordinate modules, each of a particular transaction.◦ Few afferent processes.◦ Many efferent processes.◦ Higher up levels of structure chart.◦ Concerned with coordinating the production of outputs. © 2015 John Wiley & Sons, Inc. All rights Structure
