Computerized expert system is a system used in an attempt to make a computer an expert in one specific field of study. Both facts and rules about how the facts are sued to make decisions in the field are entered in the computer. Expert systems are a branch of artificial intelligence, which analyzes how computers behave, intelligently, like human beings. Computer expert systems have been used in the medical field for well over many decades. As part of the benefits of using expert systems, they are meant to be decision-making systems, which help, but do not replace, medical personnel. They are especially useful when there is a limited, well-defined area of knowledge needed for a decision, which will be based on objectives data.