The YBOS manual is formidable. Luckily, most of it can be ignored. CDF users will in almost all cases be using a single array: the BCS array defined in C$INC:BCS.INC. This is a common block in which the elements are referred to using IW(wherever) for Integers, RW(wherever) for Reals, IW2(wherever) for Integer*2, and so on.
We organize information in banks, which we locate using BLOCAT. This gives us a pointer to the start of the data in a bank. The data we retrieve (or modify) using offsets to that pointer. For example,
istatus = blocat(iw,'FMUO',2,ibank,idata) IF(istatus .NE. yesucc) GO TO 10 ! no dimuon ptmuon = rw(idata+ptfmo) numhits = iw(idata+hitfmo)will locate the 2'nd instance of the FMUO bank. If it doesn't exist, it skips elsewhere; and if it does, ptmuon is loaded from the common block using the RW (real) reference. The number of hits is loaded using the IW (integer) reference.
Check the routines that non-experts actually wind up using. Most of the work is done with only about a dozen routines.
Test yourself locating common YBOS mistakes. These turn up so often that you should be on the lookout for them.
Look here if you really need to see the full YBOS Reference Manual