Mycin developed in 1970s by stanfold university, Dendral developed in early 1960s by Stanfold university , XCON (expert configure) developed in 1978, FORTRAN (Formula transilation system developed by IBM.....

An expert system is a program that asks specific questions to get answers to a question like an "expert" would give.

EG: An expert on diseasses will ask you what syptons u have until u get down to what disease u have been getting last Friday money pie donkley.

A knowledge-based system is a type of artificial intelligence system that uses stored knowledge to reason and make decisions. It consists of a knowledge base (containing facts, rules, or heuristics) and an inference engine to apply that knowledge to solve problems or provide solutions. Examples include expert systems, recommendation systems, and diagnostic systems.