Waterfall Model in SDLC

It is a traditional model
It is a sequential design process, often used in SDLC, in which the progress is seen as flowing steadily downwards (like a waterfall), through the different phases as shown in the figure,

Waterfall model


Requirements Collection:-
– done by Business Analysts and Product Analysts
– gathering requirements
– translates business language into software language
For eg. let us consider the example of a banking software.

Feasibility Study:-
– done by software team consisting of project managers, business analysts, architects, finance, HR, developers but not testers
– An architect is a person who tells whether the product can be developed and if yes, then which technology is best suited to develop it.
– here we check for,
– technical feasibility
– financial feasibility
– resource feasibility

There are 2 stages in design,
HLD – High-Level Design
LLD – Low-Level Design
HLD – gives the architecture of the software product to be developed and is done by architects and senior developers
LLD – done by senior developers. It describes how each and every feature in the product should work and how every component should work. Here, only the design will be there and not the code.
For eg. let us consider the example of building a house.

Coding / Programming :-
– done by all developers – seniors, juniors, freshers
– this is the process where we start building the software and start writing the code for the product.

– done by test engineers
– it is the process of checking for all defects and rectifying it.


– done by installation engineers
– to install the product at a client’s place for using after the software has been developed and tested.
For eg. consider the example of a software to be developed and installed at Reliance petrol bunk.

– here as the customer uses the product, he finds certain bugs and defects and sends the product back for error correction and bug fixing.
– bug fixing takes place
– minor changes like adding, deleting or modifying any small feature in the software product.

Note:- 100 % testing is not possible – because, the way testers test the product is different from the way customers use the product.


Drawbacks of the Waterfall Model:-
In the waterfall model, backtracking is not possible i.e, we cannot back and change requirements once the design stage is reached. Change in requirements – leads to a change in design – thus bugs enter the design – which leads to change in the code which results in more bugs. Thus the requirements are freeze once the design of the product is started.
The drawback of requirements freezing – the customer may not be satisfied if the changes he requires is not incorporated in the product. The end result of the waterfall model is not a flexible product.
The major drawback of the waterfall model – testing is a small phase which is done after coding. The requirement is not tested, the design is not tested, if there is a bug in the requirement, it goes on till the end and leads to a lot of re-work.

Advantages of waterfall model – requirements do not change nor do design and code, so we get a stable product.

Applications of the waterfall model:-
Used in – developing a simple application
– for short-term projects
– whenever we are sure that the requirements will not change
For eg. the waterfall model can be used in developing a simple calculator as the functions of addition, subtraction etc and the numbers will not change for a long time.


Interview Questions:-

  1. What is waterfall model in SDLC or Explain the waterfall model in SDLC?
  2. What are the drawbacks present in the waterfall model?
  3. What are the advantages and disadvantages of the waterfall model?
  4. What kind of applications are developed based on the waterfall model?

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