HIPO is a forms-driven technique in that standard forms are used document the information. It consists of a hierarchy chart and an associated set of input/process/output charts. HlPO captures the essence of t down decomposition; it describes the data input and output from processes and defines the data flow composition. It was developed by IBM as a design aid and implementation technique with the following objectives:
1. Provide a structure by which the functions of a system can be und stood.
2. State the functions to be performed by the program rather than specifying the program statements to be used to perform the functions.
3. Provide a visual description of input to be used and output to be 'produced for each level of the diagram. HIPO makes the transformation of input JO output data visible.
HIPO uses easy-to-draw vector-like symbols between processes that define data communicati0I1 and data direction. As shown in the procedure for generating HIPO diagrams is simple:
1. Begin at the highest level of abstraction and define the inputs to the system and the outputs from it in aggregate terms.
2. Identify the processing steps by those that convert input into output.
3. Document each element using HIPO diagram notation and the associated treelike structure.
4. Identify sub processes and their respective inputs and outputs. Continue decomposition until the processes cannot be decomposed any further.
There are two aids available for drawing HIPO diagrams: the HIPO work sheet, jacket describes the symbols. The HIPO package format consists of the following:
1. Visual table of contents shows the structure of the diagram and the relationships of the functions in a hierarchical manner, It also has a legend to show how the symbols are to be used.
2. Overview diagrams describe the major functions and reference the detail diagram(s) needed to expand the functions adequately. They provide the following:
a. The input section that contains the data items used by the process steps.
b. The output section that contains the data items created by the process steps.
c. Process section that contains numbered steps that describe the functions to be performed. Arrows connect then to the output step_ and input/output data items.
d. The extended description refers to non-HIPO documentation and code.
3. Detail diagram contains an extended description section that amplifies, the process steps and references the code associated with each process step.
It is important to use HIPD early in the design phase of a project so that designers can document their thoughts concurrently with the design process. Thus, the preparation of HIPO diagrams is a by-product of the though process of the design rather than an additional chore.
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