Agile Software Development

First i would like to start with Agile manifesto

There is no design , construction phase in agile software methodology.You have to keep your waterfall methodology fundamental outside the door.

Agile embraces the idea to design,develop,integrate,deploy project continuously.At any point of time system is ready to deploy.There is a methodology TDD ,test first and code, for testing functionality.

Manifesto for Agile Software Development

We are uncovering better ways of developing

software by doing it and helping others do it.
Through this work we have come to value:

Individuals and interactions over processes and tools
Working software over comprehensive documentation
Customer collaboration over contract negotiation
Responding to change over following a plan

That is, while there is value in the items on
the right, we value the items on the left more.

Three things are important in agile software development

1) Change is the only constant
2) Scope is the control variable
3) structure is flattened