What do major video game companys like infinity ward and bungie use to develop their games?

okay so im going to school next year for game programming and i want to know more than i know now. I know each gaming company is different with the languages and such but, do they create their own software, or use something out there that anyone can use. im a little confused about it all when it comes to that. If there are any game developers or any employee in the gaming industry reading this, can you please tell me the whole process and steps and software thats involved. Thanks in advanced. And please reply if you know what you are talking about and have a ton of experience. Thanks a lot!