The IBM Mainframe: How It Runs and Why It Survives

Slashdot reader AndrewZX quotes Ars Technica: Mainframe computers are often seen as ancient machines—practically dinosaurs. But mainframes, which are purpose-built to process enormous amounts of data, are still extremely relevant today. If they're dinosaurs, they're T-Rexes, and desktops and server computers are puny mammals to be trodden underfoot.
It's estimated that there are 10,000 mainframes in use today. They're used almost exclusively by the largest companies in the world, including