So, as you can see, when you hear someone say that they have a mainframe, it can mean different things. Sometimes, they may actually be referring to a mid-range system, such as an Application System/400 (AS/400) or Unix system. The types of mainframes that you would most like to modernize will be either IBM or Unisys, and as you can see from this chapter, they have different approaches for how you modernize them.
We will get into the actual how to modernize later in the book. For now, the intent is to show that IBM and Unisys mainframes, while somewhat similar, are different systems that need to be approached differently.
We have now covered both common types of mainframes. The next chapter will cover midrange systems, such as the iSeries (AS/400) and Advanced Interactive eXecutive (AIX).