Definition No. 5 Five-stage

In the first stage, only symbolic attributes are used to identify design concepts. In the second stage, a limited number of numerical attributes is used to conduct simplified calculations. Finally, in the last stage, all meaningful numerical attributes are used. 

The popularity of the five-stage definition was a reflection of the fact that in the 1970s and even in the 1980s the use of computers was quite expensive, not to mention very time consuming in terms of the input 

Engineering designing process is a five-stage sequential process with stages called Problem Identification, Problem Formulation, Conceptual Designing, Preliminary Designing, and Detailed Designing.  

the cost of computer calculations is so much lower with respect to the cost of manual calculations that there is no justification for using preliminary models and following the five-stage process. Therefore, today the dominant understanding of the engineering designing process is that of a four-stage process. 

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