Rest easy, people of Earth: The United States’ nuclear arsenal will no longer rely on a computer system that uses 8-inch floppy disks, in an update the Defence Department has cast as a step into the future but which some observers might be surprised to learn was required at all.

The system, called Strategic Automated Command and Control System (SACCS) “is still in use today but no longer uses floppy disks,” David Faggard, a spokesman for the Air Force Global Strike Command, which manages the Air Force portion of the arsenal, said in an email. “Air Force Global Strike Command is committed to modernising for the future.”

The update is part of a broader overhaul of the US’ atomic weapons that began under President Barack Obama and has continued under president Donald Trump. The move away from floppy disks was completed in June but was not widely reported at the time. It was reported last week by C4ISRNET, a website that covers military technology.

“The Air Force completed a replacement of the ageing SACCS floppy drives with a highly secure solid-state digital storage solution in June,” Justin Oakes, a spokesman for the 8th Air Force, said in an email. “This replacement effort exponentially increased message storage capacity and operator response times for critical nuclear command and control message receipt and processing.”

The role of floppy disks in the command and control operations of the nation’s nuclear arsenal was highlighted in a 2016 report from the US Government Accountability Office. It said the disks were used in a system that “coordinates the operational functions of the nation’s nuclear forces.”

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The report said that the Strategic Automated Command and Control System ran on an IBM Series/1 computer — a piece of hardware that dates to the 1970s — and used 8-inch floppy disks to manage weapons like intercontinental ballistic missiles, nuclear bombers and tanker support aircraft.

It warned the Pentagon was one of several government agencies whose computer systems relied on “outdated software languages and hardware parts that are unsupported,” some of which were “at least 50 years old.”

The report also cited ageing or obsolete systems at the Treasury Department, the Justice Department, the Social Security Administration and the Department of Veterans Affairs.

But a “60 Minutes” report from 2014 pointed out a perhaps unexpected upside of relying on such old technology. Because the systems are not connected to the internet, they are exceptionally secure: Hackers can’t break into a floppy disk.

All of this may leave the modern reader wondering: What is a floppy disk?

An artefact from a time when “the world was not wired,” according to Tom Persky, who inventories and sells floppy disks at what may be one of the largest such companies left, FloppyDisk.com.

Back then, if you wanted to get information like software onto a computer or a large device, you had to put it on a floppy disk, insert the disk into the machine and then direct the machine to access the information.

“There was nowhere to log into,” Mr Persky said in an interview. “There was no logging in and downloading software or data updates or anything like that.”

In a nod to the fact that some readers, even of dry government reports, may not know what a floppy disk is, the Government Accountability Office provided a photograph of two disks along with a summary of their place in the pantheon of information technology.

“Introduced in the 1970s, the 8-inch floppy disk is a disk-based storage medium that holds 80 KB of data,” it said in its report. “In comparison, a single modern flash drive can contain data from the equivalent of more than 3.2 million floppy disks.”

According to Mr Persky, whose inventory contains more than 500,000 floppy disks, the disks are more widely used than one might expect, especially in industrial machines, aircraft, medical devices and complex hardware systems like those used by the world’s militaries. He said he thought it had been roughly five years since anyone had manufactured a new disk.

“A big industrial machine that is designed to last 30, 40 or 50 years and in fact does last 30, 40 or 50 years — do you throw it away because there is a new way to get information onto the machine?” he said. “The question is, what is the cost of using the floppy disk as opposed to the cost of transitioning to something else like a USB drive or linking to the internet?”

That said, floppy disks have some advantages over other methods of information transfer, like a Wi-Fi link or a flash drive, Mr Persky said.

“We have an old technology that is not easily hackable, that is not expensive, that is extremely well understood, it is extremely stable, and as long as the bits of information you are trying to get into a machine are small, a floppy disk is a perfectly good and OK thing to use,” he said. “Is it going to be OK to use in five or 10 or 15 years? I don’t know.”

Mr Persky outlined the many drawbacks of “physical media” like floppy disks: They hold less data than can be uploaded via the internet; they are slow and expensive to distribute; you need to find a specialist repairman if the machines needed to read them break down; and, of course, no one had made a new one in five years.

“There are certainly some advantages to physical media and huge, overwhelming disadvantages to physical media,” he said. “And physical media will go away, but it just hasn’t gone away yet. That is a long, complicated, messy business. Or at least I hope.”