Can someone tell me the different kinds of mainframe systems there are or atleast name the most popular ones used by insurance companies, banks, etc? Would AS400 be considered a type of mainframe system? How do u know what kind of mainframe system ur working with? All I know is TSO ATSO. Thanks

U.S. insurance companies and banks all use IBM-compatible mainframes. The OS is MVS (written by IBM) and the mainframe itself is probably also made by IBM but may be a clone made by Hitachi or Amdahl. It used to be that mainframes differed from other systems because they could support 100s or 1000s of users, but now that a large as400 can do that also the difference is more the physical environment. A mainframe sits on a raised floor so the bulky cables can run underneath the floor and the room it is in has special air conditioning. The as400 and other systems like it are different in that they can be put into a normal office environment and the OS is way more user friendly. Recent mainframes actually do not need the special environment anymore and everything is smaller, but the cabling is as extensive as ever. As to knowing which mainframe you are using, they all have some sort of low level interface which you can query. An MVS system will have a TSO (time sharing option) environment which is similar to a DOS prompt on a PC, and from there you can query the system to find out what type of cpu it is, what os, how much memory, etc. You have to know what you are doing, just like you do in DOS.