Old and New Software Development Life Cycle

There are some Old SDLC models which are not encouraged to follow. Yet, some of the interviewers ask about these. Hence for the sake of Interview purpose we are going to discuss some of these Old SDLC models below:


  • Prototype Model (Old Model)
  • RAD Model (Old Model)
  • Incremental Model/Component Assembly Model (Old Model)
  • Spiral Model (Old Model)
  • Fish Model (New Model)
  • V- Model (New Model)
  • Agile Model (New Model)
  1. Prototype Model:
This model is follow able when there is no clarity on the requirement. In this model, customer/client ask for the sample first or they ask about the Dummy Software. We can follow this model when there is ambiguity/confusion in customer's requirement. In this software companies release dummy/sample software first. Then based on this they (software companies) try to get the clear requirements from the customer/client. After getting the clear requirement, they focus on the real development of the real software.

Dummy Model
Prototype Model or Dummy Model

2. RAD Model:

This model is called as 'Rapid Application Development Model'. In this model the existing code is used with the minor changes when there is no time. Sometimes the software is developed by just integrating the existing components or block of codes in order to save time.

3. Incremental Model/Component Assembly Model:

This model is also known as 'Installment by Installment Model'.

Installment by Installment Model
Incremental Model

This model is a method of software development where the product is designed, implemented and tested incrementally unless the development is completed. This model includes the process of Waterfall model with iterative philosophy of prototyping 

4. Spiral Model:

This model is also called as version by version testing.

Spiral Model
Spiral Model

Testing is done only at one stage in Old SDLC Models. Single stage were also done by the programmers in Old SDLC models.

In all the above SDLC Models, Organisations conduct testing only after the coding. At the testing stage some programmers used to involve but to release quality software testing is needed to be performed at multiple stages. Hence at all the stages Development Team members were separated from testers at later SDLC Models (New SDLC Models)

5. Fish Model:

This model defines the mapping between multiple stages of development and software integration. The Upper Part in the below diagram is known as 'SDLC' and The lower part is known as 'STLC'.

Fish Model
Fish Model


It is pretty much clear from this model that every development stage is being mapped with the testing stage. This model is very expensive as it demands separate testers for every single stage of testing. Here the review part is known as 'Verification Testing' and the rest of the testing is called as 'Validation Testing'.

But it has some drawbacks too like it is  very costly and there is lack of co-ordination among employees.

6. V-Model:

V-Stands for 'Verification and Validation'. This model also defines the mapping between development and testing phases.

V Model
V -Model


In this model also, separate testing team is needed for system testing/Software Testing stages because the testing stage is the bottleneck stage for the software development. For the remaining stages of testing organisations maintains same developers to conduct development and testing both.

  • Unit Testing: Testing of the program with respect to low level design (LLD) is called as unit testing.
  • Integration Testing: Testing of the Interconnection of the programs with respect to high level design (HLD) is called as integration testing ot interface testing.
  • System Testing:  Testing of a software with respect to system request specification (SRS) is called as system testing.
  • Acceptance Testing: Testing of a software with respect to Business Request Specification (BRS) is called as acceptance testing

7. Agile Model:

In this model, customer involves in each and every stage.

Agile Model
Agile Model


In this model, the developers and testers co-operates with the customer site people (mandatory) in each and every stage of development and testing. This model is suitable only for the projects not for the products. This model is followed only for application development.

Agile Model
Agile Model


In above three Advanced SDLC Models, most of the organisations are following V-Model because this model is suitable for Project Development and as well as for Product development both. This Model has decreased the cost of project/product by assigning some testing stages to the developers.