- nearly all mainframes have the ability to run (or host) multiple operating systems;
- they can add or host swap system capacity without disruption;
- they are designed to handle very high volume input and output (I/O) and emphasize throughout computing;
- a single mainframe can replace dozens or even hundreds of smaller servers;
- they excel in reliable volume computing in domains requiring complex numeral operations (e.g.: financial, indexing, comparisons etc.).
The mainframe is also known as the „big iron” and it has been associated, historically, with centralized rather than distributed computing. Some of the most popular vendors of mainframe were IBM, Hitachi and Amdahl. There have been voices to say that the mainframe is some sort of a “dinosaur” - not only because of its size, but because of the predictions (going back many years) that it would become “extinct”, at some point. For instance, in 1991, Stewart Alsop, the editor of InfoWorld, wrote that the last mainframe would be retired by 1996. However, in February 2008 IBM released a new mainframe, the z10. Nowadays, IBM emphasizes that their mainframes can be used to serve distributed users and smaller servers in a computing network.
The original mainframes were housed in room-sized metal frames, which is probably where the name comes from. In the past, a typical mainframe might have taken about 2,000 - 10,000 square feet. But newer mainframes are about the same size as a large refrigerator. Mainframe computers play a central role in the daily operations of many of the world’s largest Fortune 1000 companies: in banking, finance, health care, insurance, public utilities, government, and many public and private enterprises around the world.
“Despite the continual change in IT, mainframe computers are considered by many to be the most stable, secure, and compatible of all computing platforms. The latest models can handle the most advanced and demanding customer workloads, yet continue to run applications that were written in earlier decades. For those who think there is no use for the “big iron” now, they would really be surprised. The truth is that we are all mainframe users in one way or another.” (source)
Read more about the mainframes here.
CA Technologies created a video history of the mainframe since its foundation. Enjoy the story: