Forget the big red button; this is how the U.S. would actually conduct nuclear war.
Minuteman III missiles are capable of carrying up to three thermonuclear warheads. They range from 3-5 hundred kilotons, which is more powerful than 600 million pounds of dynamite. Right now there are over 450 Minuteman III missiles buried deep under fields in the sparsely inhabited regions of the United States. They are connected by a spider-web of thousands of miles of cables, ready to strike at top secret targets faster than you can get a pizza.
One silo, the F.E. Warren Air Force base, is home of the 90th Missile Wing. They command 150 of these Minuteman III missiles. It's hard to imagine a weapons system more powerful than the one they operate. And yet, these missiles, their launch control centers and their command capsules all operate on antiqued technology. Namely, the floppy disk. In the system, there are cursors and trackballs to navigate. It has 100 megabytes of hard drive memory, 16 megabyte of ram, and 200 kilobytes of memory. And there's only one channel of communication that uses a floppy disk to tell the system how to operate.
This was cutting edge technology back in 1971. But old technology is not necessarily a bad thing. Modern networked computers can be easily hacked and compromised with malware, and with these machines, that’s more difficult. It gives the missile silos a certain amount of security because it reduces the number of vulnerabilities.
While these computers may be from the 70s, the missileers who run these facilities, skew a bit younger. Most of them are too young to remember the Floppy Disk, not to mention Pac Man or Pong. In fact the disks they're handling are, in some cases, older than they are. The missileers look for false alarms and fake intruder signals caused by stray deer and bad weather.
Ultimately, the combination of old technology and humans is what has kept the Minuteman 3 safe so far. Although these machines might be antiquated, this is still arguably one of the most powerfully impactful computer systems in human history. So, any changes they're going to make will have to be really well thought out, and top, top secret.