Performance Evaluation of Computer Systems
Evaluating the performance of a computer system usually involves constructing an appropriate model of the system and then using the model to predict the system's behavior. The model incorporates appropriate information about the system structure or organization as well as its workload or input. Sometimes the model is analyzed using mathematical techniques; alternatively (or in addition), the model may be simulated. Analytic models describe the system with a set of equations, and are often stochastic. A simulation model is a computer program whose execution mimics the behavior of the system and from which measurements can be taken to generate performance data; simulation models are also often stochastic.

Performance is a key criterion in the design, procurement, and use of computer [and communication, AW] systems. As such, the goal of computer systems engineers, [software engineers, AW], scientists, analysts, and users is to get the highest performance for a given cost. To achieve that goal, computer systems professionals need, at least, a basic knowledge of performance evaluation terminology and techniques. Anyone associated with computer systems should be able to state the performance requirements of their systems and should be able to compare different alternatives to find the one that best meets their requirements.
There are at least two advantages to apply models like Fitts' law to empirical studies. First, the model provides predictable power beyond the task parameters, such as a set of target size and distance, tested in the experiment. Second, since Fitts' law transforms the experimental measurements to an index of performance that is independent of the specific task parameters (size and distance), it is possible to compare results across studies that do not use identical settings.
One limitation of Fitts' law paradigm, however, is that target acquisition, or pointing, is no longer the only task a computer input device is used for. Capabilities such as drawing, writing, navigating through nested menus, and moving in 3D virtual worlds all become increasingly desirable.