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Structured Program design is a set of techniques, guidelines, and a method for making program coding, testing, and maintaining easier by reducing the complexity of programs. Structured design reduces complexity of programs by breaking the programs into small pieces called modules. Ideally, each module of a program should perform a distinctive function or activity and should perform this function independently of the other program modules. A system developed using structured design is characterized by small modules that are easier to code, test, and maintain than are the few large, complex programs of an unstructured system.
The techniques used for structured program design are the Structure Chart and Program Definition Language (P.D.L.) The structure chart allows us to create an outline of a program by specifying modules and how the modules are connected. PDL is used to specify the processing of each module. Program design guidelines are rules for evaluating the complexity of modules as the structure chart and PDL are being constructed. The design method provides a procedure for identifying programs and then constructing and refining the structure chart and PDL for each program.
In this article structured program techniques, including structure chart, PDL, and related concepts such as trans form analysis, transaction analysis, refining the program design specifications coupling, cohesion, module size, fan - out and fan - in are discussed.