99 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 drive?

Floppy drives came first because early PCs often had two of them and no hard drive 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 belied its name: reviewers found 10.0 slow and unfinished, without even DVD playback, and six months later Apple made the 10.1 upgrade free to everyone who owned it.

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

Digital cameras were the plan: a platform for 'smart cameras' that linked to PCs. The team then reworked the very same system for phones as the smartphone market took off.

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 a day, daily ones for a month and weekly ones beyond that, then quietly deletes the oldest when the backup drive fills up.

Chromebooks outsold Apple's Macs over a full year for the first time in 2020, lifted by a boom in what?

Remote schooling had districts and parents buying over 30 million Chromebooks in 2020. The Mac's own share grew that year, so those sales came mostly out of cheap Windows laptops.

Apple's 2025 jump from iOS 18 straight to iOS 26 arrived with which translucent new interface design?

Liquid Glass came with a renumbering: Apple named every one of its systems 26, after the year ahead, so that the iPhone, Mac, iPad, Watch and TV software finally share one number.

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 and sign-in credentials behind a hardware barrier, and Microsoft called it a 'critical building block' for its Windows Hello and BitLocker protections.

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 has Mark Shuttleworth's company Canonical bankrolled since its first release in 2004?

Ubuntu, a Nguni word for humanity, was paid for out of the fortune Shuttleworth made selling his internet-security firm to VeriSign, money that had already bought him a ride into orbit.

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 a separate unit, pledging to preserve its independence and neutrality so that it could go on working with IBM's rivals.

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 let one hung program freeze the whole machine on classic Mac OS and 16-bit Windows?

Cooperative multitasking relies on each program voluntarily yielding the CPU; Windows 95 and Mac OS X both moved on to preemptive scheduling, in which the system forcibly shares out the 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, parks a program's idle pages on disk until needed?

Virtual memory lets programs address more RAM than is physically installed, and when a machine spends most of its time shuffling pages in and out 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 takes its name from the routine itself: since the earliest editions of Unix, the core of the system has called a function named panic when it hits an error it cannot recover from.

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 ran Mars Pathfinder in 1997, when engineers reproduced the lander's repeated computer resets on a duplicate on Earth and cured them with a software patch sent to Mars.

Unix began as a pared-down answer to which sprawling time-sharing project that Bell Labs had just walked away from?

Multics was a joint venture of Bell Labs, General Electric and MIT; the Bell researchers who quit it built a small replacement whose name, Unix, puns on it.

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 named its Unix successor 'Plan 9' after a cult film by which director, often called the worst ever?

Ed Wood's Plan 9 from Outer Space supplied the title; the system's lasting gift is UTF-8, which Ken Thompson sketched for it on a diner placemat in 1992.

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 sh that shipped with 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 stopped fitting once sudo learned to run a command as any account, not only the all-powerful root, so the project itself now reads the name as su 'do'.

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.

Bill Gates said in 2013 that using Ctrl+Alt+Delete for which Windows task was a mistake, having wanted a single button?

Logging in: Ctrl+Alt+Delete was devised by engineer David Bradley as a quick way to restart the original PC, and Gates said the keyboard's designer had refused him a dedicated button.

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 almost two decades at 10?

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

Rosetta first appeared in 2006 to carry PowerPC software onto Intel Macs, was retired in 2011, and came back in 2020 to do the same favour for Intel software on Apple's own chips.

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 takes its name from which naturalist?

Charles Darwin got the nod when Jobs unveiled the freely shared core in 1999 with the words 'it's about evolution'; the same Darwin code 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 lost its co-author when Windows 3.0 became a runaway hit in 1990: Microsoft walked away from the partnership and turned its work on the next version into Windows NT.

By 2025, QNX, the real-time OS that BlackBerry bought in 2010, was running in more than 275 million of what?

Cars: BlackBerry built its PlayBook tablet and BlackBerry 10 phones on QNX, and though it has since retired both, the same software lives on behind digital dashboards and driver-assistance systems.

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

Ingenuity, a small helicopter, flew on a Qualcomm Snapdragon 801, a processor built for smartphones, running Linux, after riding to Mars tucked under the Perseverance rover.

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

MINIX 3 runs inside Intel's Management Engine, beneath whatever system the owner installed, which may make a classroom exercise the most widely used OS in the world. Tanenbaum learned of it from the press.

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

Gentoo, named after the fastest-swimming penguin, builds its software to order on each machine instead of shipping ready-made packages, which is why Google moved ChromiumOS onto it in 2010.

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' scene was real software from which company?

Silicon Graphics' fsn, short for File System Navigator, was a real demo for its workstations, and Lex's line holds up: the machine ran IRIX, the company's own version of Unix.

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

Zircon began life under the name Magenta, and it sets Fuchsia apart from Android and ChromeOS, which both sit on Linux.

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.

Which Rolling Stones song did Microsoft license for the advertising campaign that launched Windows 95?

Start Me Up was picked as a nod to the brand-new Start button. Reports put the fee at $8 to $14 million, though Microsoft said it paid about $3 million.

Which ambient-music pioneer and former Roxy Music member composed the brief chime heard as Windows 95 loads?

Brian Eno wrote the chime after two Microsoft designers approached him in 1994. In 2025 it was chosen for the Library of Congress's National Recording Registry.

Windows XP's default wallpaper, a green hill photographed by Charles O'Rear, carries which one-word title?

Bliss shows a real hillside in January 1996, bare of vines because a pest outbreak had forced the vineyard to be cleared. It may be the most viewed photograph in history.

Which card game, bundled with Windows 3.0 in 1990, quietly taught newcomers to drag and drop with a mouse?

Solitaire was meant to soothe people intimidated by the operating system, and shuffling cards between piles made the unfamiliar drag-and-drop gesture feel natural.

Which name belongs to the penguin mascot of Linux, drawn by Larry Ewing in 1996 for a logo contest?

Tux was first said to stand for Torvalds's Unix, though it also suits a bird that looks dressed in a tuxedo. Ewing drew it in an early version of the free image editor GIMP.

Which key combination, devised by David Bradley as a quick reboot, did Bill Gates call a mistake for Windows logins?

Ctrl+Alt+Delete replaced Bradley's first idea, which was too easy to bump by accident. The new trio could not be pressed with one hand on the original PC keyboard.

In November 2017, Linux became the only operating system left on the TOP500 list of the world's fastest what?

Supercomputers lost their last two non-Linux entries that month, a pair of AIX machines that had slid to 494th and 495th place on the list.

At Apple's 2002 developer conference, Steve Jobs staged a mock funeral, coffin included, for which operating system?

Mac OS 9 got the send-off because Apple had stopped developing it, and the stunt told programmers it was time to move their apps to Mac OS X.

Which name for a Unix background process did MIT programmers borrow from Maxwell's molecule-sorting thought experiment?

Daemon was coined at MIT's Project MAC around 1963 for programs that toil unseen on system chores. Its supposed origin as an acronym was invented afterwards.

Which research centre built the Alto, the 1973 computer whose mouse-driven desktop Steve Jobs saw on a 1979 visit?

Xerox PARC gave Apple's staff the demonstrations in exchange for the right to buy Apple stock, and the ideas resurfaced in the first mass-market computers with a graphical interface.

Which unit of execution shares memory with its siblings inside one program, unlike processes, which are walled off?

Thread is the name for the smallest run of instructions a scheduler can manage on its own. An early version appeared in 1967 in a batch system that called them tasks.

Which signal makes a processor pause its running code so the operating system can handle a keypress or mouse movement?

Interrupt signals are usually traced to 1953's UNIVAC 1103A, and faulty hardware that fires them nonstop can choke a computer in what engineers call an interrupt storm.

Which word, coined by Ascher Opler in 1967, describes low-level code built into hardware such as a motherboard chip?

Firmware was Opler's label for the layer between hardware and software, and it stuck for the code that wakes a PC before any operating system loads.

Which kind of small program, such as GRUB on Linux, starts an operating system's kernel when a computer powers on?

Bootloader room was once brutally tight: on classic PCs the first stage had to squeeze into a single 512-byte sector.

Which name does Unix give its all-powerful administrator account, whose numeric ID is always zero?

root may have earned the name as the only account allowed to alter the top-level directory, which goes by the same word.

Which security mechanism, required by Apple for every App Store app, confines a program so its failures cannot spread?

Sandbox comes from the box of sand that children dig in, where anything can be built or wrecked without doing damage in the real world.

Which power-saving state copies everything in RAM to disk so a computer can switch off fully and later resume?

Hibernation first shipped in 1992 on a Compaq laptop. Ordinary sleep, by contrast, keeps sipping power to hold the contents of RAM.

Which diagnostic way of launching Windows, long reached by pressing F8 at power-on, offers only minimal features?

Safe Mode is meant for repairs rather than everyday work. On Intel Macs the equivalent, Safe Boot, is reached by holding the Shift key at power-on.

On Unix, which name is given to a process that has finished running yet keeps its slot in the process table?

Zombie processes linger until the parent reads their exit status, at which point they are said, in keeping with the metaphor, to be reaped.

Apple's 1997 purchase of which company brought Steve Jobs back and supplied the foundation for Mac OS X?

NeXT cost Apple $427 million. Years earlier, Tim Berners-Lee had used one of its computers to build the world's first web server and browser.

Beginning with Mavericks in 2013, Apple switched from big cats to naming macOS releases after places in which US state?

California is where Mavericks, a famous surfing spot, breaks off the northern coast. That release was also the first free upgrade since Mac OS X 10.1.

Which Mac file manager, shipped since the first Macintosh in 1984, wears the smiling-screen Happy Mac face as its icon?

Finder has outlasted every overhaul of the Mac, and a version of it even ran on a different Apple computer, the Apple IIGS.

Which Microsoft desktop release, built under the codename Longhorn, introduced the glassy translucent Aero look?

Windows Vista had a famously drawn-out birth: work on it began in May 2001, five months before Windows XP had even gone on sale.

The 'XP' in Windows XP, the system Microsoft unveiled under that name in February 2001, is short for which word?

Experience was the word. The project's earlier codename, Whistler, honoured the British Columbia ski resort where many Microsoft employees went skiing.

On which day of the week did Microsoft begin releasing its monthly batch of Windows security fixes in October 2003?

Tuesday became the fixed monthly slot in the wake of the Blaster worm, a schedule meant to cut the cost of distributing fixes. Attackers studying each batch gave the following day its own nickname, Exploit Wednesday.

Which dessert name did Android 1.5 carry in 2009, the first public release in a long run of sweet-themed versions?

Cupcake began a theme dreamed up by project manager Ryan Gibson, which Google kept going for a decade before switching to plain numbers in 2019.

Which operating system, descended from Psion's EPOC, was the world's most popular on smartphones until the end of 2010?

Symbian lost its lead to iOS and Android, and in 2011 Nokia outsourced its upkeep to Accenture, moving 2,800 employees across with the work.

Which version-control tool did Linus Torvalds begin writing in April 2005 to manage development of the Linux kernel?

Git was born of necessity: the free licence for BitKeeper, the proprietary tool that kernel developers had relied on since 2002, had just been revoked.

Raspberry Pi OS, the official system for the tiny single-board computer, is based on which Linux distribution?

Debian names its releases after Toy Story characters, and its own name blends Debra, the first name of founder Ian Murdock's then-girlfriend, with Ian.

Edsger Dijkstra's P and V operations, named from Dutch words, act on which construct that rations shared resources?

Semaphore dates from 1962 or 1963, when Dijkstra's team was writing an operating system for the Electrologica X8. In his earliest paper on the idea, V stood for vrijgave, Dutch for release.

The lock that programmers call a mutex, used to guard data shared between tasks, takes its name from which phrase?

Mutual exclusion was first identified and solved as a problem by Edsger Dijkstra, in a 1965 paper credited with founding the study of concurrent algorithms.

Which bug, among the flaws of the deadly Therac-25 radiotherapy unit, makes a program's result depend on timing?

Race condition is a term older than most software: engineers were using it by 1954 in work on switching circuits. The Therac-25 errors killed at least three patients.

Which exception does the memory management unit raise when a program touches memory not yet loaded into RAM?

Page fault handling is how an operating system supplies memory on demand, fetching data only when it is touched. On a hard disk each fetch could cost several milliseconds.

Which term describes a computer so short of RAM that it mostly shuffles data to and from disk instead of working?

Thrashing sets in when RAM is overcommitted. The chunks of memory a program touches most often are called its working set, and trouble begins once those no longer fit.

A Linux system can set aside which kind of dedicated partition to hold chunks of memory pushed out of RAM?

Swap can also live in an ordinary file, and since the 2.6 series of Linux kernels that has been virtually as fast as a dedicated partition.

Which software layer, such as Xen or VMware ESXi, lets one physical computer run several operating systems at once?

Hypervisor is a twist on supervisor, an old word for an operating system's kernel: it is the supervisor of the supervisors.

Which technique queues documents so a slow printer can work through them while the computer gets on with other tasks?

Spooling may take its name from Simultaneous Peripheral Operations On-Line, though that phrase could equally have been made up later to fit the word.

Which crash snapshot of a program's memory is named after the magnetic memory that dominated computers until the 1970s?

Core dump files began as paper printouts, columns of octal or hexadecimal numbers that let programmers debug without tying up a hugely expensive computer.

Which mechanism does a program use to ask the kernel for a service, such as opening a file or creating a process?

System call requests are rarely written by hand: on Unix-like systems programmers use wrapper functions in the C library, usually named the same as the request they pass on.

On Unix-like systems, which program is the ancestor of every other process and is typically given process ID 1?

init automatically adopts any process whose own parent has exited, so that orphaned programs are never left without a guardian.

On x86 processors, which of the four numbered protection rings gives an operating system's kernel the most privilege?

Ring 0 sits at the centre, while ordinary apps run out in Ring 3, where even switching on a webcam has to go through more privileged code.

Which Bell Labs colleague of Ken Thompson created the C language and shared the 1983 Turing Award with him for Unix?

Dennis Ritchie later described Unix and Linux alike as the continuation of ideas that he, Thompson and many others had set in motion years before.

Which programmer announced the GNU Project on Usenet in September 1983, aiming to build a free Unix-like system?

Richard Stallman chose a name that is a joke in itself: GNU stands for GNU's Not Unix, an acronym that contains its own abbreviation.

Abraham Silberschatz's textbook Operating System Concepts is nicknamed after which animals on its first cover?

Dinosaurs on that cover were each labelled with an old operating system, the biggest beasts standing for the oldest, to make the point that systems evolve as well.

Which carmaker's research division co-wrote, in 1956, an early mainframe operating system with North American Aviation?

General Motors built it to launch each new program automatically the moment the previous one finished, the idea known as batch processing.

Microsoft built MS-DOS on 86-DOS, a system it first licensed in December 1980 from which small hardware maker?

Seattle Computer Products had 24-year-old Tim Paterson write it for the firm's own computer kit, and staff knew it as QDOS, the Quick and Dirty Operating System.

Apple licensed the name iOS in 2010 from which networking company, to head off a possible trademark lawsuit?

Cisco had used IOS as the name of the software on its routers for over a decade. Apple's own system had been called iPhone OS until the rebrand that June.

Sony's PlayStation 4 system software, known as Orbis OS, is built on which open-source Unix-like operating system?

FreeBSD turns up in surprising places: Netflix delivers its video from servers running it, WhatsApp relied on it for years, and the Nintendo Switch borrows parts of it too.

Which computer's crash notice, 'Guru Meditation', began as a joke about its developers calming down on a Joyboard?

Amiga's makers had earlier sold the Joyboard, a foot-operated controller for the Atari 2600, and sitting cross-legged on it became their cure for crash-induced rage.

Linus Torvalds was studying computer science in which Nordic city when he began the Linux kernel in 1991?

Helsinki is also where he kept the files for about half a year under the name he preferred, Freax, a blend of free, freak and the x of Unix.