Software Development Life cycle model important concept and question

Waterfall Model

In waterfall model ,a working model of the software is only available at a very later stage therefore there is no room for correction/changes.

It is mainly used when the developers have clear idea of the software and they have built similar software in the past.

Increment process

In increment process model, similar steps to waterfall model are applied but after each cycle a new version of the product is released. This process is continued till we develop the desired software. This model is used when the concept of the software is not that clear at the starting.

Spiral model

Spiral model is like an evolutionary model of waterfall model, in spiral model project risk factor is taken into consideration and the steps followed are planning,risk analysis,development,assessment. It is a model in which we study about how make the software.