application development models

What are the 5 application development models?
There are three types of models: incremental, iterative and a combination.

1. Waterfall Model
Goes through design stages in order, but with the option to return to the 
previous stage if needed. It's an incremental model.

2. Iterative Model
One part of the app is worked on through all the stages until it's complete, 
this is one iteration. There can be endless iterations. It is repeated until 
a final, complete system is produced. It's an iterative model.

3. Agile Development Model
Allows a system to be worked on and refined iteratively. Development may
begin with a small part of the system that is added to through each cycle. 
It's a combination of incremental and iterative.

4. Rapid Application Development (RAD) Model
Less time producing requirements, specifications and design. Prototypes 
are worked on iteratively, refining prototypes into the final product. 
They are tested during development and at end of production of each new 
prototype. Testing requires customer feedback to assess and evaluate each 
prototype. (opposed to leaving their input to the later stages of the model, 
when it's too late)

5. Spiral Model
Uses prototypes that are worked on and refined as the phases are worked 
through repeatedly. It's a combination of incremental and iterative, 
it is made with features of incremental, waterfall or evolutionary 
prototyping models.