2. Automatic theorem proving:
Mathematicians are believed to be super intelligent creatures, and so in its early childhood AI tried to show intelligence by creating machines capable of proving theorems by themselves. By having some basic assumptions and rules, they tried to prove theorems by combining these rules, getting new assumptions and so on. Gelernters program for geometry theorem proving was a typical example. Later it was realized that the intelligence of human experts in this area is not easily imitable, and the use of common sense and knowledge about mathematics was needed to prove theorems. Currently not many developments are taking place in this area.

3.Natural language processing (NLP)
Languages like English, French or Malayalam, which are used by men, are called natural languages. The language we speak is often context sensitive. "Did you shoot the tiger?” has different meanings when asked to a hunter and a photographer. Also our language is incomplete. Natural language processing deals with understanding this language using knowledge about the grammar rules and context. This has a wide variety of applications and is a field of active research. Also translation between these languages is studied in AI.

4. Vision, Speech recognition and similar areas.
Seeing an animal and recognizing it as a cat is child's play, but a difficult task for computers. Modern AI programs focuses on recognizing objects and persons and behavior based on vision. This has many applications in robot navigation, crime detection, military operations and so on.