Modular Design and Packaging

Object Oriented Design: Modular Design and Packaging

• Software design has two components: modular design and packaging.
• Modular design decomposes a program into modules, which are groups of executable instructions with a single point of entry and exit.
• Packaging involves assembling data, process, interface, and geography design specifications for each module.
• Structured design, developed by Ed Yourdon and Larry Constantine, breaks up a program into a hierarchy of modules for easier implementation and maintenance.
• Structured design requires drawing data flow diagrams (DFDs) for the program, which may represent modules on a structure chart.
• Logical DFDs need to be revised to include editing, error handling processes, and internal controls.
• Transform analysis is an approach used to derive a program structure chart from program DFD.
• Transform analysis involves dividing processes into those that perform input and editing, processing or data transformation, and output.
• The afferent includes processes that perform input and editing, the central transform includes processes that transform data, and the efferent includes processes that do output.
• Tracing the sequence of processing for each input helps identify the afferent, central transform, and efferent portions.
• A structure chart is created to communicate the modular design of the program.
• The structure chart involves creating a commander and chief module, second-level modules for afferent and efferent processes, and modules for transformation processes.