Agile development model is also a type of Incremental model. Software is developed in incremental, rapid cycles. This results in small incremental releases with each release building on previous functionality. Each release is thoroughly tested to ensure software quality is maintained. It is used for time critical applications. Extreme Programming (XP) is currently one of the most well known agile development life cycle model.

Advantages of Agile model:

1.Customer satisfaction by rapid, continuous delivery of useful software.
2. People and interactions are emphasized rather than process and tools. Customers, developers and testers constantly interact with each other.
3.Working software is delivered frequently (weeks rather than months).
4.Face-to-face conversation is the best form of communication.
5.Close, daily cooperation between business people and developers.
6.Continuous attention to technical excellence and good design.
7.Regular adaptation to changing circumstances.
8.Even late changes in requirements are welcomed

Disadvantages of Agile model:

1.In case of some software deliverables, especially the large ones, it is difficult to assess the effort required at the beginning of the software development life cycle.
2.There is lack of emphasis on necessary designing and documentation.
3.The project can easily get taken off track if the customer representative is not clear what final outcome that they want.
4.Only senior programmers are capable of taking the kind of decisions required during the development process. Hence it has no place for newbie programmers, unless combined with experienced resources.