The FLASHCARDS give you an easy way of mastering the 16 Type Codes. They show the two favorite functions, and the specific attitude of both (in or out). In about 1/2 hour, you will have all 16 Type Codes down pat -- it is much easier than it looks at first. This is sort of like learning multiplication tables, except easier. I hope that you find the FLASHCARDS helpful in decoding and mastering the codes.