Waterfall Model

Waterfall Model
This is classical model has systematic, in a series in build software. There are two descriptions from waterfall model. even if both use different phase names, but the main is same.
Phases in waterfall model (Pressman)

Phases in waterfall model (Sommerville)

Explanation
1. Requirements definition >>> gather need in its entirety then analyzed and be defined need everything that must be filled by software that be built. this phase must be done in its entirety to be able to produce complete design.
2. System and software design >>> design is done after need finished gatherred in its entirety. determine system architecture as a whole.
3. Implementation and unit testing >>> program design has translated into codes by using programming language that determined. program that built direct tested.
4. Integration and system testing >>> program units unification then tested as a whole (system testing). after system testing, software is sent to user.
5. Operation and maintenance >>> operate program in that area and do maintenance, like to setting or change because adaptation with situation actually. maintenance includes correction and various error yg tdk found in previous stages, repair on system unit implementation and system service development.
Weakness Of Waterfall Model
1. difficulty in contribute change after process is endured.
2. previous phase must complete and finished before do phase next.
Problem on waterfall model
1. difficult change is done because in character stiff.
2. because the stiff character, this model fit when need be be gatherred in its entirety so that change can be depressed as little as may be. but practically consumer/user that can give need in its entirety.
3. in general used for big system engineer where project is done at several places differ, and divided to be some part sub-proyek.