But just to confuse you, on Star Alliance carriers, the convention is to use "C" to refer to Business Class - essentially F/J(orC)/W/Y refer to the most expensive fare code for the various cabins, which for Star Alliance is generally "C" but for everyone else "J". Up until recently "P" class (for "Premium") wasn't really used, but with some carriers wanting to distinguish their normal First class from what they think it is a separate product (SQ P referring to their Suites class and EY P referring to their Residence product) you might see that code thrown about too

On Flyertalk it's quite an interesting (for a Flyertalk geek like me anyway...it's not actually "interesting") shibboleth to see the usual carriers that a person travels in (or at least perhaps when their impressions of frequent flying were forged) by how they refer to a cabin by its shortened code, aka, J or C, or Y+ or W.

P.S. W refers to Premium Economy - more likely seen on BA and VA.