Conversion of Categorical Propositions - "Prior Analytics" Book I Ch. II - Aristotle

Chapter II is very short and is basically showing how conversion can be done with the four categorical propositions, or as Aristotle calls them in chapter III, "apodeictic premisses" and in De Interpretatione "simple sentences". 

Converting E
The universal negative statement is convertible in its terms. No S is P. = No P is S.

Examples used: No pleasure is good. Therefore, No good is pleasure. No B is A. Therefore No A is B. 

Converting A
The universal affirmative is partially convertible in its terms (not as a universal, but as a particular). All S is P. ≠ All P is S. (but can = Some P is S.)

Examples used: Every pleasure is good. Therefore some good is pleasure. All B is A. Therefore B is some A. 

Converting I
The particular affirmative is convertible in its terms. Some S is P. = Some P is S.

Examples used: Some pleasure is good. Therefore, some good is pleasure. Some B is A. Therefore Some A is B. 

Converting O
The particular negative is not convertible in its terms. Some S is not P. ≠ Some P is not S.

Examples used: Some animals are not man. It is not equivalent to say that Some man is not animal.  Some B is not A. It is not equivalent to say Some A is not B.