50 Fun Facts About Operating Systems

The 'DOS' in MS-DOS, the command-line software Microsoft first shipped for PCs in 1981, was short for what?

Disk Operating System was a generic phrase, and the very same code also shipped on the original PC under the badge PC DOS, with rival clones borrowing the name too.

MS-DOS reserved the drive letters A: and B: for which hardware, leaving C: for the first hard disk?

Floppy drives came first because early PCs often had two of them and no hard disk at all, and Windows has honoured the leftover C: ever since.

Android 4.4 was co-branded with which chocolate bar under a promotional deal struck with Nestlé?

KitKat was agreed in a phone call to Nestlé and sealed at Mobile World Congress in February 2013, and in the US the bar is actually made by Hershey under licence.

Which big cat codenamed Mac OS X 10.0, the 2001 release that began Apple's run of feline version names?

Cheetah was followed six months later by version 10.1, which Apple released on 25 September 2001 as a free update for everyone who had bought 10.0.

Android Inc., bought by Google in 2005, originally set out to build an OS for which devices?

Digital cameras were the plan until investors balked, and in April 2004 the team pivoted to phones as a rival to Symbian and Windows Mobile.

Windows 10 was offered as a free upgrade for its first year to owners of which earlier versions?

7, 8 and 8.1 owners got twelve months to upgrade free, part of Microsoft's aim of a billion devices on Windows 10 within three years, a mark it reached only in March 2020.

Which Apple utility, shipped with Mac OS X Leopard, restarts an Intel Mac into a full copy of Windows?

Boot Camp only ever made sense on Intel chips, and Apple dropped it entirely for Apple silicon Macs, which can run ARM Windows only inside a virtual machine.

Which Mac OS X Leopard backup feature lets users scroll back through hourly snapshots of their files?

Time Machine keeps hourly backups for the past day, daily ones for the past month and weekly ones beyond that, until the backup disk runs out of space.

In 2020 Chromebooks outsold which rival machines for the first time, by taking share from Windows laptops?

Apple's Macs were overtaken during the remote-schooling boom of 2020, when cheap Chromebooks swallowed sales that would otherwise have gone to Windows laptops.

In 2025 Apple jumped straight from iOS 18 to which version number, a year-based label shared by every Apple OS?

26 is a year-based label: the software serves the year after its autumn release, and Apple applied the same convention to every one of its platforms at once.

Windows 11's 2021 requirements excluded millions of capable PCs by demanding version 2.0 of which security chip?

Trusted Platform Module 2.0 keeps encryption keys in hardware, and Microsoft called it a 'critical building block' against firmware and hardware attacks.

Which two makers shipped the first Chromebooks in June 2011, weeks after Google unveiled them at its I/O conference?

Samsung and Acer got there first because Google's own Cr-48 test laptop of 2010 was only ever given away to pilot users and never sold.

Microsoft's 2016 Anniversary Update let PC users run a real bash shell natively via which new compatibility layer?

Windows Subsystem for Linux at first implemented Linux system calls inside the Windows kernel; WSL 2, announced in 2019, switched to running a real Linux kernel in a lightweight virtual machine.

Which Linux distribution, bankrolled by Mark Shuttleworth, is named from a Nguni word for 'humanity to others'?

Ubuntu has shipped a new version every six months since its first release in October 2004, each one named after an animal with an alliterative adjective.

Which company agreed in October 2018 to buy Red Hat, the enterprise Linux firm, for about $34 billion?

IBM closed the deal in July 2019 and kept Red Hat as an independent subsidiary, which stayed among the largest corporate contributors to the Linux kernel.

FAT32, the file system commonly used on USB sticks, cannot hold a single file larger than what size?

4 GB minus one byte is the ceiling, which is why one large video file refuses to copy onto a FAT32 stick until it is reformatted as exFAT, FAT's successor.

Which multitasking scheme of classic Mac OS and 16-bit Windows relies on each program voluntarily yielding the CPU?

Cooperative multitasking let one hung program freeze the whole machine, which is why Windows 95 and Mac OS X both moved to preemptive scheduling that forcibly shares time.

Edsger Dijkstra's dining philosophers puzzle, five thinkers sharing five forks, illustrates which multitasking hazard?

Deadlock strikes when every philosopher grabs the fork on the left and waits forever for the right one, and operating systems face the same trap with locks on files and memory.

Which technique, pioneered on Manchester's Atlas computer, lets programs address more RAM than is physically installed?

Virtual memory parks idle pages on disk and pulls them back on demand, and when a machine spends all its time doing that the condition is called thrashing.

What do Linux and macOS call the fatal crash that Windows users know as the blue screen of death?

Kernel panic is the Unix-family term, and Mac OS X 10.2 to 10.7 announced one with a multilingual message telling the user to restart the computer.

Microsoft's own 1991 video said the initials of Windows NT, its 32-bit line launched in 1993, stood for what?

New Technology was the gloss in a 1991 Bill Gates video, but by 1998 Gates was saying the letters no longer carried any specific meaning at all.

Which real-time operating system from Wind River ran NASA's Curiosity rover and the Mars Reconnaissance Orbiter?

VxWorks also flew on the 1994 Clementine lunar probe and the earlier Mars rovers Spirit and Opportunity, a résumé few operating systems can match.

Unix began as 'Unics', a pun on which sprawling time-sharing project that Bell Labs had just walked away from?

Multics was a joint venture of Bell Labs, General Electric and a university partner, and the Bell researchers who quit it built Unix as a pared-down replacement.

Ken Thompson's wish to keep playing which game of his own on a spare Bell Labs minicomputer helped spark Unix in 1969?

Space Travel simulated a flight through the solar system, and rewriting it for a cast-off PDP-7 is how Thompson came to write the first pieces of Unix.

In 1992 Andrew Tanenbaum declared 'Linux is obsolete' on Usenet because Torvalds had spurned which design for its core?

Microkernel designs push drivers and file systems out of the privileged core, as Tanenbaum's own teaching system did, yet the monolithic Linux went on to win the world.

Bell Labs' research successor to Unix took the name 'Plan 9' from a 1957 film by which notoriously inept director?

Ed Wood's Plan 9 from Outer Space supplied the title, and the system's lasting gift was UTF-8, which Ken Thompson invented as its native text encoding.

Bash, the default command shell on most Linux systems, is a pun on the surname of which earlier shell's author?

Stephen Bourne wrote the original sh for Version 7 Unix in 1979, and Brian Fox's 1989 'Bourne Again SHell' was the GNU project's free replacement for it.

The Unix command 'sudo', which runs a single command with administrator rights, was originally short for what?

Superuser do lets an ordinary account borrow root's powers for one command, which is why Linux how-to guides are littered with it.

In preemptive multitasking, what is the term for the few milliseconds a process gets before the scheduler moves on?

Time slice, also called a quantum, is what a frozen program can no longer hog: when it expires the core forcibly hands the processor to the next process in line.

In which CPU mode do ordinary apps run, with the hardware itself refusing any privileged instruction they attempt?

User mode is the fenced-off side of the divide; the core of the OS runs with unrestricted power, and every system call is a controlled crossing between the two.

Apple File System, rolled out to iPhones by iOS 10.3 in 2017, replaced which Mac format in use since 1998?

HFS+, also called Mac OS Extended, dated from the original iMac era, and since High Sierra every Mac with flash storage is converted to APFS automatically on upgrade.

Which 2019 macOS release was the first to refuse to run 32-bit apps?

Catalina runs 64-bit software exclusively, so every Carbon-era program and QuickTime 7 itself stopped launching the day users upgraded.

Which 2020 macOS release bumped the version number from 10 to 11 after sixteen releases under the 'Mac OS X' banner?

Big Sur was also the first macOS able to run on Apple silicon, so the new number marked a new chip as much as a new look.

Which Apple translation layer, revived in 2020 for Apple silicon, lets a Mac run software built for its previous chips?

Rosetta takes its name from the Rosetta Stone that unlocked hieroglyphs, and Apple described the invisible layer as 'the most amazing software you'll never see'.

Which Mac OS X interface, unveiled at Macworld in January 2000, had buttons Steve Jobs said you would want to lick?

Aqua's water-drop buttons and gel scroll bars lasted until OS X Yosemite flattened the look, though the name survives for the whole Mac interface.

The classic Mac alert sound 'Sosumi', added in System 7, was cheekily named after a court battle with which company?

Apple Corps, the Beatles' company, had settled with Apple on condition it stayed out of music, so the new sound's name was read aloud as 'so sue me'.

Apple's open-source Unix core beneath macOS and iOS was named, with Jobs citing 'evolution', after which naturalist?

Charles Darwin got the nod from Jobs with the words 'because it's about evolution', and the same Darwin core now sits under iPadOS, watchOS, tvOS and visionOS too.

Which 1987 DOS successor did Microsoft co-develop with the maker of the original PC before abandoning it for Windows?

OS/2 outlived its desktop hopes in the back office: Suncorp's ATM network in Australia was still running it in 2002, and some ski-resort ATMs later still.

QNX, the real-time OS that BlackBerry bought in 2010, has been designed into more than 270 makes and models of what?

Cars by the million: QNX runs the infotainment, navigation and telematics units of more than 270 vehicle makes and models, and BlackBerry bought it in 2010 from audio firm Harman.

Which NASA craft made the first powered flight on another world in April 2021, running Linux on a phone chip?

The Ingenuity helicopter flew on a Qualcomm Snapdragon 801, a chip from mid-2010s phones, running Linux, after riding to Mars tucked under the Perseverance rover.

Planning the iPhone in 2005, Steve Jobs said he could either 'shrink the Mac' or enlarge which existing Apple product?

The iPod route lost: Jobs set a Mac team under Scott Forstall against Tony Fadell's iPod team, and Forstall's side won by building iPhone OS out of Mac OS X.

Which Andrew Tanenbaum teaching OS quietly runs inside the management engine of Intel chips since 2015's Skylake?

MINIX 3 runs on a tiny Quark x86 core inside Intel's Management Engine, below and invisible to whatever OS the user installed on the machine.

Google's ChromeOS is derived from ChromiumOS, which is itself built on which Linux distribution?

Gentoo is named after the fastest-swimming species of penguin, and it compiles its software from source code rather than shipping ready-made packages.

Valve's SteamOS 3, rebuilt for the Steam Deck's 2022 launch, is based on which rolling-release Linux distribution?

Arch's rolling updates let Valve push driver fixes quickly, and the same system is the default on Valve's later Steam Machine and Steam Frame hardware too.

The 3D file browser in Jurassic Park's 'It's a Unix system! I know this!' scene was real software from which company?

Silicon Graphics' fsn navigator ran on its own IRIX flavour of Unix, and the film showed it on an SGI Crimson workstation in 1993.

Google's Fuchsia, which replaced the software on the first Nest Hub in 2021, runs on a newly written core named what?

Zircon was originally named Magenta, and it makes Fuchsia the one Google operating system not built on Linux, unlike Android and ChromeOS.

Which feature-phone OS, forked from Firefox OS, powers India's JioPhone and the revived Nokia 8110 'banana phone'?

KaiOS beat iOS into second place in India in a May 2018 market-share study, with Android at 71%, thanks largely to the cut-price JioPhone.

What was the name of the dogcow, the half-dog half-cow beast demonstrating page layout in classic Mac OS?

Clarus says 'Moof!', a blend of moo and woof, and Apple's developer support adopted her as its mascot, documenting her solemnly in Technote 31.

Which 2009 Mac OS X release, marketed as having 'zero new features', cost $29 against $129 for earlier versions?

Snow Leopard's $29 price bought a release that mostly tightened the engine underneath, and it was the first Mac OS X to drop PowerPC Macs entirely.

Huawei's HarmonyOS, unveiled in August 2019, made its debut on which kind of product?

Smart TVs from Huawei's Honor brand came first, and until 2024 the system was built by combining the Android Open Source Project with Huawei's own OpenHarmony.