<P> During the design and development of new products, designers and engineers rely on both a bottom - up and top - down approach . The bottom - up approach is being utilized when off - the - shelf or existing components are selected and integrated into the product . An example would include selecting a particular fastener, such as a bolt, and designing the receiving components such that the fastener will fit properly . In a top - down approach, a custom fastener would be designed such that it would fit properly in the receiving components . For perspective, for a product with more restrictive requirements (such as weight, geometry, safety, environment, etc .), such as a space - suit, a more top - down approach is taken and almost everything is custom designed . However, when it's more important to minimize cost and increase component availability, such as with manufacturing equipment, a more bottom - up approach would be taken, and as many off - the - shelf components (bolts, gears, bearings, etc .) would be selected as possible . In the latter case, the receiving housings would be designed around the selected components . </P> <Dl> <Dd> Part of this section is from the Perl Design Patterns Book . </Dd> </Dl> <Dd> Part of this section is from the Perl Design Patterns Book . </Dd> <P> In the software development process, the top - down and bottom - up approaches play a key role . </P>

What is top to bottom approach in c