Bloomberg has tons and tons of legacy code, mostly in Fortran and C, and to add insult to injury, it's rarely commented/documented/explained in any shape or form -- when you make a function call, you often enter magic land. While there are no new Fortran files (company policy), you will almost certainly have to at least look at lots of Fortran in debugging it, and you may need to make code additions for bug fixes.
Bloomberg is a fast paced company (due to it being driven by Finance), but this means that you focus on getting the final product done ASAP -- which can be exciting -- but rarely will you get the chance to take time and properly design and develop a product, or refactor old code that, while not technically broken, is inefficient.