The functional requirements for a system describe what the system should do. These requirements depend on the type of device being developed, the expected users of the device, and the general approach taken by the organization when writing requirements. When expressed as user requirements, functional requirements are usually described in an abstract way that can be understood by system users. However, more specific functional system requirements describe the device functions, its inputs and outputs, exceptions, etc., in detail. For example, here are examples of functional requirements for the reading device in Sinhala language for visually impaired people through the braille system, These requirements have a specific order to the priority, but for easy of explaining following order may bit different from the correct order. [1] Turn on the Braille character display [21] Turn the device off When user select this option, Braille character display is turns on and resets di...