Spirial model

Spiral Model
Combines the featured of the prototyping model and the water fall model.
Being used for large, expensive and complicated projects

Steps

1. The new system requirements are defined in as much detail s possible and a preliminary design is crated for the system
2. First prototype of the new system is construction from the preliminary design.This is usually a scaled down system and represents an approximation of the characteristics of the final product
3. The preceding steps are iterated untill the customer is satisfied that the refined prototype represents the final product desired.

we use version of spiral model called Agile..
Example in auto industry.
Software designing same thing
In banking account. someone designed -screen where you can lgin and that takes you to static url and then brings you to another image. (thats prototype)
POC (proof of concept).
This is what we show to business partners