The performance of a software application indicates the responsiveness of the operations that it can perform. Users have greater expectations today in terms of the responsiveness of the applications that they use. They demand fast response times regardless of their location or the device that they are using.
Most importantly, software must serve its functional purpose, be reliable in its operation, and provides its functionality in a usable way. If it does not, then the speed of the application will not matter. However, once those needs are met, performance is of high importance.
