Okay, let me explain IBM S/360 like I would to a 5-year-old:
IBM S/360 is kind of like a really big toy box. It's a big, special box that has lots of different parts and tools inside. And just like how you can use different toys to build different things, people can use the parts and tools in the S/360 box to make different kinds of computer programs that do different things.
The S/360 toy box was made by a company called IBM, which is short for International Business Machines. They made it a long time ago, back in the 1960s. And at that time, computers were still kind of new and not many people had them. So the S/360 was a really important invention because it made it easier for more people to use computers.
One of the things that made the S/360 box special was that it was what's called a "mainframe" computer. That means it was big and powerful and could do a lot of things at once. It was kind of like having a really smart and strong robot that could do all sorts of tasks, like keeping track of numbers or sorting through information.
Lots of big companies and government agencies used the S/360 toy box to make different computer programs. For example, they might have used it to keep track of how much money they were making or to organize all the different parts of a project they were working on.
And even though the S/360 was invented a long time ago, some people still use it today! That's because it was really well designed and built to last a long time. So it's like a super cool and useful toy that people have been playing with for over 50 years!