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difference between functional and non functional requirement

what are the difference between functional requirements and non functional requirements.and what is meant by functionality.why we maintenance separate environment for development and testing

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  Functional Requirements are related to functionality of the system/application.
  But Non functional requirements are more related to the performance of the system/application. 

FUNCTIONAL requirements are related to the functional part of an application ( as u know these requirements r given by the customer ) and NON-FUNCTIONAL requirements r related to the performance or speed of an application ( these explicit requirements are planned and done by the BUSINESS ANALYST ). these non functional part are comes in coding only 

I think now can understand

thanks for u r reply.here customer means client is it crct

Non functional parts does not comes under coding.. its wrong..

Functional Requirement that specifies a function that a component or system must perform.

Non Functional Requirement  that does not relate to functionality , but to attributes such as reliability , efficiency , usability , maintainability and portability .

Functionality is the capacity of the software product to provide functions which meet stated and implied needs when the software is used under specified conditions.

We maintain separate environment  for developers and testers because when developers wil be busy in coding @ the same time testers cant test the developing s/w.. when developers give one exact build to the testers then tat wil be taken in testers environment nd testing wil be done.. 

Hi Swathi,

Functional requirements are the requirements put by the stakeholders which are related to the functional features or business logic of the application. If we consider a mailing application then functional requirements will be something    like : Mails are getting delivered correctly to the recipient or not etc.

But non-functional requirements are the requirements put by the stakeholders which are not related to the functional features of the product. Considering the same application, non-functional requirements will be like : How user friendly the application is, how much time it takes to deliver the mail etc.

Separate environment for development and testing is needed because testing and development are two completely different activities. In development activity, developers need some environment where they can develop the system     in a better way and for testers they need a environment which is same as the environment where the application is going to be used. Another reason could be like : during testing activity testers don't want to show the test results to the developers.

With best regards                                                                                                                                  Sitam


  a non-functional requirement is a requirement that specifies criteria that can be used to judge the operation of a system, rather than specific behaviors. This should be contrasted with functional requirements that define specific behavior or functions. The plan for implementing functional requirements is detailed in the system design. The plan for implementingnon-functional requirements is detailed in the system architecture.

In general, functional requirements define what a system is supposed to do whereas non-functional requirements define how a system is supposed to be. Functional requirements are usually in the form of "system shall do <requirement>", while non-functional requirements are "system shall be <requirement>".

Non-functional requirements are often called qualities of a system. Other terms for non-functional requirements are "constraints", "quality attributes", "quality goals", "quality of service requirements" and "non-behavioral requirements". Qualities, that is non-functional requirements, can be divided into two main categories:

  1. Execution qualities, such as security and usability, which are observable at run time.
  2. Evolution qualities, such as testability, maintainability, extensibility and scalability, which are embodied in the static structure of the software system.

Functional req : based on the requirements of the application

Non functional: this is more related to the systemsa behaviour in terms of not the functionality of the application, but it mainly depends on the scalibity , no of Vusers the application can withstand.. in genrally we can say it is of more related to Performance of the application. In the performance testing, we check how mnay Vusers the applictaion can stand for how much long time). even small things like (Page is opened and u can see at the top right corner of the page, there is minimize,restoredown and close button, this is also called as nonfucntional requirement)  and few more like when u r restoring or when ur altering/sizing the page, the data/ words whicha re displaying on the page should be fully displayed).. it goes on.... like this Swathi.. there r plenty of more where we can elobrate and tell..


Santhosh Palvai


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