Waterfall Model

It is a simplest model, which states that the Phases are organized in a linear order. The model was originally proposed by “Royce”.

The various phases in this model are shown below:-

(1) Analysis Phase: It consists of planning and requirements definition activities. The end products of planning are – (a) System definition (b) project plan

(a) System definition – It is typically expressed in English. It incorporates charts, figure, graphs, tables and equation of various kinds.

(b) Project plan – It contains the life cycle model to be used, the preliminary development schedule, preliminary cost estimates and resources estimates, tools & technique to be used.

(2) Design Phase: This phase is concerned with – (a) identifying software components like functions, data streams and data stores, (b) Specifying software structures, (c) Maintaining a record of design decisions and providing blue prints for the implementation phase.

(3) Implementation Phase: It involves the translation of the design specifications into source code. It also involves activities like debugging, documentation and unit testing of the source code. In this stage various styles of programming can be followed like built-in and user defined data types, secure type checking, flexible scope rules, exception handling, concurrency constructs etc.

(4) System Testing Phase: It involves three kinds of activities: - (a) Unit testing (b) Integration testing (c) Acceptance testing

(a) Unit testing - Unit testing focuses on the smallest unit of software design i.e. the software component or module. Using the component-level design description as a guide, important control paths are tested to uncover errors within the boundary of the module. The unit test is white box oriented. Selective testing of execution paths is an essential task during the unit test. Boundary testing is the last and one of the most important tasks of the unit.

(b) Integration testing - Integration testing is a systematic technique for constructing the program structure while at the same time conducting tests to uncover errors associated with interfacing. The objective is to take unit tested components and build a program structure strictly as per design. The program is constructed and tested in small increments, where errors are easier to isolate and correct.

(c) Acceptance testing – Acceptance testing involves Planning & Execution of various types of tests in order to demonstrate that the implemented software system satisfies the requirements stated in the requirements document.

(5) Maintenance Phase: In this phase the activities include (a) Enhancement of Capabilities (b) Adaption of software to new processing environments and (c) Correction of software design. 

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