System Development Models Class 12 Computer Science

Here are there types system development models for instance Waterfall model, Spherical Model  Prototyping Model

1.Waterfall Model 

  • The Waterfall Model was the first Process Model to be introduced.

  •  It is very simple to understand and use. 

  • In a waterfall model, each phase must be completed before the next phase can begin and there is no overlapping in the phases.

  • The Waterfall model is the earliest SDLC approach that was used for software development.

  • The waterfall Model illustrates the software development process in a linear sequential flow. This means that any phase in the development process begins only if the previous phase is complete.

  • Phases do not overlap.

  • It is the fundamental process of activities, development, validation and evolution.

Waterfall models the first model of system development modelsFig: Waterfall Model 

Requirement  analysis −

  • First stage of waterfall model.

  • Identify the actual requirement, requirement analyze, prioritize.

(All possible requirements of the system to be developed are captured in this phase and documented in a requirement specification document.)

System Design − 

  • It is the system design architecture phase where. Specifics of requirement like(hardware,software ) 

  • Defining the overall overall system architecture.

(The requirement specifications from the first phase are studied in this phase and the system design is prepared. This system design helps in specifying hardware and system requirements and helps in defining the overall system architecture.)

Implementation −

  • It is the programming phase of the system development process.

  • With inputs from the system design, the system is first developed in small programs called units.

  • Each unit is developed and tested for its functionality, which is referred to as Unit Testing.

Integration and Testing − 

  • This is the integration and testing phase of all developed units.

  • It is the complete system test to ensure that the software requirements have been met or not. 

(All the units developed in the implementation phase are integrated into a system after testing each unit. Post integration the entire system is tested for any faults and failures.)

Deployment of system − 

In this phase  Once the functional and non-functional testing is done; the product is deployed in the customer environment or released into the market.

Maintenance − There are some issues which come up in the client environment. To fix those issues, patches are released. Also to enhance the product some better versions are released. Maintenance is done to deliver these changes in the customer environment.

2. Prototyping Model 

  • Software prototyping is becoming very popular as a software development model, as it enables us to understand customer requirements at an early stage of development.

  • The prototyping model is applied when detailed information related to input and output requirements of the system is not available. In this model, it is assumed that all the requirements may not be known at the start of the development of the system. 

  • It is usually used when a system does not exist or in case of a large and complex system where there is no manual process to determine the requirements.

  • These systems are then continuously modified until the user is satisfied.

Prototyping Model of System Design Models

  1. Identify the user needs:

  • This step involves understanding the very basics product requirements especially in terms of user interface.(interview phase of user )
  1. Develop a prototype 

  • The initial Prototype is developed in this stage, where the very basic requirements are showcased and user interfaces are provided.
  • Define one or more prototype tools to use in software development. 
  1. Determine if prototype is acceptable 

  • The prototype developed is then presented to the customer and the other important stakeholders in the project.

  • The system analyst provides an opportunity from becoming familiar with the new system.

  • The user advises the analyst whether the prototype is satisfactory.  If so, then the next step, else the prototype is revised by repeating step 1,2 and 3 with a better understanding of the user need.

  1. User the prototype  

  • This is the final step of the software development process. Prototype becomes the operational system. 

  • This step is only possible to complete  when the prototype tools work properly in user requirement.

Advantages and Disadvantage of Spiral Models 

Advantage  Disadvantage 


 Provides a working model to the user early in the process, enabling early assessment and increasing user's confidence.

If the user is not satisfied by the developed prototype, then a new prototype is developed. This process goes on until a perfect prototype is developed. Thus, this model is time consuming and expensive.


The developer gains experience and insight by developing a prototype there by resulting in better implementation of requirements.

The developer loses focus of the real purpose of prototype and hence, may compromise with the quality of the software.


The prototyping model serves to clarify requirements, which are not clear, hence reducing ambiguity and improving communication between the developers and users.

Prototyping can lead to false expectations. For example, a situation may be created where the user believes that the development of the system is finished when it is not.


There is a great involvement of users in software development. Hence, the requirements of the users are met to the greatest extent.

The primary goal of prototyping is speedy development, thus, the system design can suffer as it is developed in series without considering integration of all other components.

3.Spiral Model

  • Spiral model is one of the most important Software Development Life Cycle models, which provides support for Risk Handling.

  • In its diagrammatic representation, it looks like a spiral with many loops. The exact number of loops of the spiral is unknown and can vary(change from one condition, form, or state to another) from project to project.

  • Each loop of the spiral is called a Phase of the software development process. The exact number of phases needed to develop the product can be varied(variety) by the project manager depending upon the project risks.

  • As the project manager dynamically determines the number of phases, the project manager has an important role to develop a product using spiral model.

Spiral model of system development models


  • The project is reviewed to see whether to continue  with a further loop of the spiral. 
  • If it is decided to continue plans are drawn up for the next phase of the project

Risk Analysis:

  • Identification software development  project and project risk. 
  • Identification of potential risk is done while risk mitigation(the action of reducing risk ) strategy is planned and finalized.
  • If requirements are not suitable, a prototype system may be developed.  

Software Development

  • After the risk evolution a development chosen. 
  • If user interface risk is dominant, an appropriate development model might be evolutionary prototyping.  
  • It includes testing, coding and deploying software at the customer site  

User Evaluation 

  • Specific objectives for the phase of the project are defined by the evaluation of the user.
  • Evaluation of software by the customer. Also, includes identifying and monitoring risks such as schedule slippage(the action or process) and cost overrun

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