Structured Design

Structured design is a data-flow-based methodology. The approach begins with a system specification that identifies inputs 'and outputs and describes the functional aspects of the system. The system specifications, then are used as a basis for the graphic representation-data flow diagram (DFD)-of the data flows and processes 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.

Structured design partitions a program into small, independent modules. The are arranged in a hierarchy that approximates a model of the business area and is organized in a top-down manner with the details shown at the bottom. Thus, structured design is an attempt to minimize "

Complexity and make a problem manageable by subdividing it into s segments, which is called modularization or decomposition structuring minimizes intuitive reasoning and promote maintainable, provable systems.

A design is said to be top-down if it consists of a hierarchy of mod each module having a single entry and a single exit subroutine. The advantages of this design are as follows:

   1. Critical interfaces are tested first.

   2. Early versions of the design, though incomplete, are useful enough resemble the real system.

   3. Structuring the design, per se, provides control and improves morale.

   4. The 'procedural characteristics define the order that determines processing.

So structured design arises from the hierarchical view of the application rather than the procedural view. The top level shows the most important division of work; the lowest level at the bottom shows the detail.