The interface of a new system, will for the most part, be a software one. However a lot of new systems may include a hardware interface as well. Consider a game such as guitar hero (pictured below). The game comes with a software element and a hardware element. As such the interface requirements will have to consider how the gamer will interact with both the game and the hardware. Also how will the hardware and software interact? These considerations are vital to produce a good working end product. Interface requirements will very much depend on the end user and also the complexity of the new system. As such it is imperative that detailed analysis has already been carried out on what the user may require.

A common mistake is to confuse interface requirements with interface design. We are, at this stage, not worried about how the interface will look or how the user would interact with the interface. The decision to have 3 or 5 buttons on the guitar is not important at this stage. What we are interested is how the interface must conform in order to be considered suitable by the end user. So guitar hero's interface requirements would be things like "the hardware must be durable with large accessible buttons to be used by people with less manual dexterity" or "the software interface must be immediately accessible by a beginner gamer".