Originally Posted by CDTraveler

As to the why of the codes: are you old enough to remember multi copy paper tickets? The kind that had to come out of a special printer, and you'd tear out a coupon for each flight leg?

They had to cram a whole lot information on a form about 3" by 7" and putting a single code letter in a box made more sense than typing out "coach class", "14 day advance purchase fare" and whatever other details were needed for their system. Once you learn the codes it's easy to read the ticketing info. There's lots of resources here on FT to help you learn the codes.