functional and non functional requirements code example

Example 1: non functional requirements

Non functional requirements are requirements that specifies and judges the operation of a system, rather than the behaviours. It defines the system attributes such as security, maintainability, usability, reliability and performance. In other words, non-functional requirements define how a system is supposed to be

Example 2: functionality which not in the requirements

It may take serious effort to determine
 if an application has significant unexpected
 or hidden functionality, and it would
 indicate deeper problems in the software
 development process. If the functionality
 isn't necessary to the purpose of the
 application, it should be removed, as
 it may have unknown impacts or dependencies
 that were not taken into account by the
 designer or the customer. If not removed,
 design information will be needed to determine
 added testing needs or regression testing needs.
 Management should be made aware of any
 significant added risks as a result of the
 unexpected functionality. If the functionality 
 only effects areas such as minor improvements
 in the user interface, for example, it may 
 not be a significant risk.