Here's our updated A-Z of technology jargon explained. Let us know in the comments if there are any confusing words or acronyms you want us to explain. Updated, 2nd October 2014
Periodically we'll update this article to explain more Apple-related technology terms in plain English.
What is 802.11 (a, b, g, n, ac)?
These are different types of Wi-Fi (or AirPort) technologies. IEEE 802.11, to give the technology its technical title, is a set of wireless specifications created by the Institute of Electrical and Electronics Engineers. They create a set of wireless specifications and companies like Apple follow them to ensure that devices (such as the iPhone) can talk to other devices (such as Internet Routers).
The various different flavours of 802.11 Wi-Fi have different speeds, power requirements and so on. 802.11ac is the most recent to be ratified and offers an estimated multi-station WLAN throughput of upwards of 1 gigabit per second; 802.11ac is covered by Apple's most recent AirPort Extreme wireless router.
What is a 3D printer?
A new type of printer that builds 3D objects, typically made from plastic. These can be virtually any shape, and it is possible to download 3D designs and build the object at home.
What is 3G?
This is a network technology used to to deliver internet data over the mobile phone network. You need to sign up for Internet Data with your mobile phone company to access 3G or 4G networks. Also known as Mobile Broadband.
What is 4G (LTE)?
4G and LTE (Long Term Evolution) are new types of mobile internet. They offer faster speeds and greater reliability than the 3G network. While it will eventually replace 3G, for now both networks run side-by-side and a device like the iPhone can access both 3G and 4G (as well as lesser known standards like Edge). Most mobile phone providers are now offering 4G along with 3G as standard, for either the same price or a slight increase. Coverage is limited to the larger cities but expected to roll out to cover 98 per cent of the country.
What is 4K?
A new type of television and monitor that is hoping to replace high-definition. 4K stands for 4,000 and is so named because it will have around 4,000 horizontal pixels. This comapres to the 2,560 x 1,440 found on a current 27-inch iMac. Although actual resolutions still vary, the most common is 3840x2160 pixels, which is four times larger than a high definition television set. Editing 4K video is very demanding on a computer, and the new Mac Pro is designed to be capable of 4K video editing.
What is an accelerometer?
This is a motion detector sensor that Apple first introduced in the iPhone. It is now found in the iPhone, iPod touch and iPad. It is the sensor that detects which way up you are holding the device, so the screen can rotate accordingly. Some games (and other apps) use the accelerometer as an input control (twisting the iPhone to recreate the movement of a steering wheel, for example)
What is accessibility?
Features offered by devices and operating systems that ensure the device can be used by people with visual or physical impairments.
What is Address Book?
Mac OS X program used for storing the names and addresses of people you know. Called Contacts on iOS devices.
What is Airplane Mode?
A simple feature of iOS that switches off all cellular, wireless and Bluetooth activity on an iPhone or iPad. You won't be able to pick up emails or tweets, access Game Center or (obviously) browse the internet. Can be switched on via the Settings app or, in iOS 7, from the Control Centre. It's designed to make smartphones and tablets safe for use on a plane, but in our experience you'll probably still be asked to switch the device completely for take-off and landing.
What is Android?
A mobile phone operating system platform created by Google. Android and iOS (the iPhone and iPad system) are the two largest mobile operating systems in the world.
Android differs from iOS in that it's an open-source system, which means that product manufacturers can adapt the original code to create custom operating systems for their devices. Amazon famously did this with its Kindle device, replacing many Google services with its own.
What is Apple Script?
Easy-to-learn Mac OS X programming language created by Apple to automate programs.
What is an app?
Short for application: the name that Apple gave to programs you install on iOS and Mac OS X devices. (However, there are such things as pre-installed apps, and on non-jailbroken iOS devices you won't be able to delete these.)
What is the App Store?
A program on iOS and Mac OS X that enables you to purchase free and paid-for software from Apple.
What is an Apple ID?
An account used to make purchases from the Apple Store. Also used to access other apple services like iCloud and Find My iPhone. Can be set up from Settings > iCloud in iOS and Settings > iCloud in Mac OS X.
What is Apple Maps?
A replacement for Google Maps first launched in iOS, and to be integrated with the Mac OS X in Mavericks. Controversial because some people claimed Google Maps was a better service.
What is Arrangement Mode?
Mode that enables you to rearrange the icons on an iOS home screen or within Dashboard in Mac OS X. Identified by the 'jiggling' around of icons and small crosses appearing at their top-left corners. Accessed by holding down any individual app icon for a second or two. Quit Arrangement Mode by pressing the Home button.
What is Bluetooth?
Technology used to wirelessly transmit data between devices. Principally used to attach accessories (Keyboard and Mouse) to Mac OS X and iOS devices. Also used to transmit music to compatible speakers. Named, incidentally, after a viking king (a vi-king?), as you can discover in our roundup of tech term origins.
What is Bluetooth 4.0?
The latest version of Bluetooth found on the iPhone 4S. It is a low-power standard, which means it can be turned on and left on without causing a drain on the battery. This has enabled services like AirDrop to be possible. Bluetooth 4.0 still drains the battery when connected to a Bluetooth device like a Apple Wireless Keyboard.
What are Cloud Services?
Cloud services store information on a remote computer, known as a Cloud Server. An intenret connected device, like an iPhone or Mac, can then access the information as its required. Cloud Servers can also help devices along with computational tasks. Apple’s own cloud service is called iCloud.
What is Contacts?
The iOS version of Address Book. Used to store details of people you know.
What is Control Centre?
New feature in iOS 7 that enables quick access to many settings and features of device. Accessed by sliding finger up from the bottom of the screen. (Pleasingly, it is indeed spelled 'centre' rather than 'center', at least on iOS devices in this country.)
Control Centre is one of the features we discuss in our video '7 things we love about iOS 7'.
What is Dashboard?
Feature in Mac OS X that displays icons for programs installed on the Mac OS X computer (similar in style to the Home Screen on iOS devices).
What is DisplayPort?
A high performance digital interface used primarily to connect a laptop or computer to a display (monitor). It can include both audio and vidoe, and also supports other forms of data like USB. Most Macs use the same interface as Lightning to run Displayport.
What is the Dock?
Feature at bottom of iOS and Mac OS X home screen/desktop that contains icons for commonly used apps. On Mac OS X can also contain folders and documents and the Trash Can.
What is Do Not Disturb?
Mode on iOS devices that blocks phone calls and makes the phone run on silent. Useful for meetings, public events and bedtime. Repeated calls to the iPhone will be let through after three rings on the default settings, but you can tweak the way it works. You can even set it to allow through VIP callers only.
What is an ebook?
An electronic book. Made popular by the Amazon Kindle device and also purchased on iOS devices using iBooks. These are books that can be read on digital devices.
What is FaceTime?
Video conferencing technology implemented into iOS and Mac OS X technology. Enables users to easily start video conversations with other FaceTime users.
What is a fanboy?
Disparaging term used, often, by other fanboys who subscribe to a different type of fandom. Google Android supporters may call users of Apple products fanboys, thereby accusing them of slavish devotion and unthinking, cultish defensiveness. In the reverse situation the variant 'fandroid' might be used instead. Also heard frequently when discussing rival gaming platforms.
We gathered a few of the more entertaining or aggressive flame comments we've had from Android fanboys (many of them accusing us of being Apple fanboys) in our article Best (and worst) of the Android fanboys: Our 15 favourite troll comments.
What is firmware?
Firmware is program code stored within hardware that determines how it works. Unlike hardware, which is fixed, firmware can be updated (like software). However, firmware updates are infrequent. Firmware updates to Apple hardware are typically handled by Software Update.
What is Find My iPad/Find My iPhone?
App for iOS devices and iCloud web-based service that enables users to locate iOS and Mac OS X devices (iPhones and Macs, and so on). Integrates with Apple Maps and enables users to lock and send messages to missing devices.
What is flame? (And what is flame-bait?)
Flame and flaming are internet terms that refer to abusive (and usually profanity-laden) comments, most commonly posted anonymously on social forums and gaming chat rooms, but also in the comments section of news and comment articles. Journalists whose work is published online quickly develop a thick skin, or learn not to read the comments below their articles.
Ironically, an article that attracts a lot of flame may be considered a success in pure web traffic terms, as the flaming process gains momentum and other users are attracted to the spectacle. This may lead to other commenters accusing the writer of creating the piece as 'flame-bait' - that is to say, a deliberately 'bad' or controversial article designed intentionally to stir up argument and attract trolls or abusive commenters.
What is a flick?
A gesture used in iOS. Made by moving the finger swiftly in any direction (usually up or down). Often used to quickly move up and down a web page or through a long list of items.
What are gestures?
A set of finger movements that you use to interact with touch screen devices like the iPhone and iPad. Common gestures include 'flick', mentioned above; pinch or 'unpinch' (opposite gestures performed with a finger and thumb), and tap.
What is a GPS?
A sensor found inside the iPhone and iPad that helps it determine its position. Used principally in Maps to locate your position on earth. GPS stands for Global Positioning System and works by linking to a network of 24 satellites in orbit around the earth. Apple combines GPS along with triangulation of known Wi-Fi hotspots and mobile phone towers to determine your position. Collectively it refers to these as Location Services.
What is High Definition? (What does HD stand for?)
A video format with a greater resolution than standard definition. Typically more than 720 horizontal lines, although often more than 1080 lines. The three main formats are 720p, 1080i and 1080p. The i stands for Interlaced which blends frames together, whereas the P stands for Progressive which shows one complete frame then the next. P is generally considered better for film and i for fast-moving television.
What is a Home button?
(Pre-Touch ID Home buttons are known to stop working, unfortunately. If your iPhone's Home button isn't responding, try this fix.)
What is a home screen?
The main screen that displays available apps and folders in iOS. You can flick left and right to show more apps and folders.
What is HomeKit?
HomeKit is a developer framework by Apple - a software platform around which other companies will create a variety of home-automation products that can be controlled via iOS devices. More here: What is HomeKit? We examine Apple's plans to automate your home via your iPhone
What's a hotspot?
A Wi-Fi hotspot is a point where you can access the internet wirelessly; you might find hotspots in various public locations, such as cafés and libraries. You can also create your own Wi-Fi hotspot using your iPhone.
Also worth mentioning what a hotspot is not.
What is iBooks?
App created by Apple to display e-books. See: iBooks 2 review.
What is the iBookStore?
Apple store used to access free and purchased iBooks. Part of the iBooks app in iOS, or can be accessed through iTunes on Mac OS X.
What is iCloud?
A range of cloud services offered by Apple. Notable features include push email, contact sync, calendar sync, Find My iPhone/iPad and iTunes Match.
What is an IMEI, and what does IMEI stand for?
IMEI stands for International Mobile [Station] Equipment Identity. Each mobile phone has a unique IMEI identifier, used for the purposes of listing stolen phones and various other things.
It's easy to find out your iPhone's IMEI: How to find your iPhone's IMEI number
What is iMessage?
Service offered by Apple that enables users to send SMS-style text messages between Mac OS X and iOS devices. Free to send but requires both users to have an Apple ID. If iMessage is not available message is sent from iPhone using SMS instead (which is charged for).
What is the Internet of Things?
The Internet of Things (or IoT) is the currently fashionable term for web- or app-connected devices and appliances outside the traditional realm of tech: cooking appliances, central heating and so on. We look at this in more detail in our article What is the Internet of Things? The best devices to connect to the iPad and iPhone.
What is iOS?
The operating system software used on the iPhone, iPod touch and iPad. The most recent full version is iOS 8. See more: What is iOS, should I update iOS, how to downgrade to an earlier version of iOS and more
What is an iPad?
Tablet computer made by Apple. Similar to the iPhone but with a larger display. Four models are available: the iPad 4 with Retina display; the iPad Air; the iPad mini 1 and the iPad mini 2 with Retina display. The first two have 9.7in screens, while the smaller minis have a 7.9in screen. We expect new iPads to appear near the end of October 2014 - most likely two from the iPad 6, iPad Pro and iPad mini 3.
What is an iPhone?
A mobile phone and portable data connected computer made by Apple. There have been 10 models released, with various configurations of each: different storage capacities, cellular connectivity and colours. Current models available: iPhone 5c; iPhone 5s; iPhone 6; iPhone 6 Plus.
What is an iPod?
A music player made by Apple: one of the most successful product lines in its history, although one that's now on the decline. The most modern incarnation is called iPod touch and is essentially an iPhone without the mobile data connection. But Apple still sells more music-focused iPods: the tiny iPod shuffle and the small iPod nano. The relatively big iPod classic was recently discontinued, causing a certain amount of grieving: A Tribute (and Goodbye) to Apple's iPod Classic.
What is IPS?
A type of LCD monitor that offers better colour reproduction. IPS stands for in-plane switching and it is widely considered superior to TN (twisted nematic) monitors. Apple MacBooks, iPads, iPhone and iPod touch models all use IPS displays.
What is iTunes?
Media player/management software made by Apple. Originally designed to play and sync music with the iPod. Modern incarnation carries out a wide range of duties from playing music, video, TV shows, storing iBooks, podcasts, apps and managing iOS devices.
What is iTunes Match?
iCloud Music service offered by Apple that enable users to sync and stream music from multiple iTunes accounts. Free version works with music purchased from iTunes Store, but a paid-for £21.99 per year service works with all your music.
What is the iTunes Store?
Digital store used to purchase music, movies and television shows. Accessed through iTunes app.
What is iTunes University? (What does iTunes U stand for?)
Part of iTunes Store that enables you to download free video and audio lectures from the world's leading universities. We explain the benefits and features of iTunes U in a separate article: Everything you need to know about iTunes U, and how to get the most out of it.
What is jailbreaking?
When you jailbreak an iPhone or iPad, you remove the locks and restrictions Apple puts into place so that you can only install officially approved apps from the Apple App Store. A jailbroken can run non-approved apps, most likely from the Cydia marketplace.
There are risks and drawbacks to jailbreaking, but it's relatively easy and many users swear by it. If you're interested, check out our tutorial: How to jailbreak an iPhone or iPad.
What is a Lightning connector, port, cable or dock?
Lightning is the name Apple gives to the connection port used to connect its most recent iPhone, iPod touch or iPad models to the mains for charging, or to a computer for charging and sync. Older models - such as the iPad 2, which has since been discontinued - use the older 30-pin dock, which is wider.
Lightning dock, on an iPad mini 2 with Retina display
30-pin port, on an iPhone 4
What are Location Services?
Feature in iOS and Mac OS X that enables apps to determine your current location. Uses a mixture of GPS and triangulation of nearby Wi-Fi hotspots and Mobile data masts.
What is Lock?
Feature on iOS devices used to fix the display in either vertical or landscape orientation. Accessed via Control Centre.
What is a Mac?
What is a MacBook?
Apple's term for a Mac laptop computer. Several models are available, split into the more powerful MacBook Pro units, and the ultra-slimline MacBook Air models.
What is a Mac mini?
A small desktop computer sold without a keyboard, monitor or mouse. See Mac Mini 2014 preview.
What is a Mac Pro?
Apple's high-end desktop computer. Looks a bit like a shiny little bin but is a lot better at video editing. (See new Mac Pro review)
What is Mail?
Stock program used to read email. It's installed with Mac OS X and iOS devices.
What is Multi-touch?
The iPhone and iPad display enables touch screen interaction using more than one finger (digit) at a time. A good example of this can be seen in the iOS game Eliss Infinity, in which you have to move planets around the screen at great speed. You will generally be moving at least two or three planets at any one time, and the game can handle up to five fingers at the same time.
What is NFC?
Near field communication is a technology that enables devices to pass information across a very short distance. Typically just a couple of centimeters. Although it’s called near field, the general idea is to allow devices to tap each other to exchange information. One mooted use for NFC would be to allow phones to act as payment devices, much like the latest generation of tap-to-pay of credit cards. Apple has not implemented NFC in any of its devices.
What is Newsstand?
Program used to download and read digital versions of newspapers and magazines. It's one of the stock apps that are pre-installed in iOS, and you can't delete it from an iPhone or iPad unless you jailbreak. But at least you can hide it in a folder if you're not interested; in iOS 6 you couldn't even do that.
What is Notification Centre?
Feature in iOS and Mac OS X that enables you to view recent messages and alerts on the device. On an iPhone or iPad, you access Notification Centre by swiping downwards with a finger from the top of the screen.
What is Objective C?
Programming language created by Apple and used to develop Mac OS X and iOS software.
What is 'pinch to zoom'?
Gesture made on iOS devices and Mac trackpads. Made by pinching finger and thumb together on screen, or 'unpinching' them apart. Often used to zoom in on items (web pages, photographs, and so on). Technically speaking it's usually the 'unpinch' that zooms into maps and so on, whereas the pinch zooms out, but we still call the feature 'pinch to zoom' in a general sense.
What is Photo Booth?
Program for iOS and Mac OS X that captures self portraits. Often combined with humorous effects.
What is Photo Stream?
iCloud service that shares recently captured photographs across multiple iOS and Mac OS X devices.
What is Push?
Push notifications are notifications that can be sent immediately to you on your iPhone. Push is often a type of e-mail service, as opposed to IMAP or POP. With Push enabled e-mails that are sent to your iPhone appear immediately on the device. The opposite of Push is Fetch, a system where the iPhone checks for e-mail in regular intervals (typically once every 15 minutes). iCloud is a Push service, so new e-mails and changes to the Calendar and Contacts are sent to other devices immediately.
What is QuickTime?
Video compression technology used by apple to distribute movies across the web. Also the name of a program used on Mac OS X to watch and share video clips.
What's the Refurbished store?
Apple's Refurbished store is great place to pick up bargains.
The products there are pre-owned, but Apple checks them over thoroughly and replaces any worn-out components before putting them on the store. You get a one-year warranty, too. It's the best place to find Macs and iPads that Apple no longer sells new, and always worth a look before buying new - there could be a bargain. The latest generation of products won't be on there, however, so don't expect a bargain on the most recent iPad Air, for instance.
What is a Retina display?
Apple's marketing term for the sharp displays featured on many Mac OS X and most iOS devices. Features a high resolution (comparative to size of display) that packs around 300 pixels into an inch, although the pixel density required to qualify as Retina in Apple's book depends on how far the average user will hold the device from their face - so full-size iPads are rated as Retina at a lower pixel density than iPhones.
The pixel density of Retina displays is considered more than the human eye can pick out individually, so it's fooled (in theory) into thinking it's looking at a real thing, rather than a picture of the thing on a screen.
What is a Retina HD display?
The step beyond Retina.
The only screens currently rated as Retina are those on the iPhone 6 and iPhone 6 Plus. It's not entirely clear what criteria are used to differentiate between Retina and Retina HD screens, but it evidently isn't pixel density, since the iPhone 6 has the same pixel density (326ppi) as its plain-Retina predecessors. (The iPhone 6 Plus, however, has a considerably higher spec: 401ppi.)
It seems that Retina HD is defined as offering wider viewing angles, better contrast, an improved polariser (which lets you view the screen more easily when wearing sunglasses) and a higher resolution - which in this case essentially translates to 'bigger screen'.
What is Safari?
Web browser software included with iOS and Mac OS X devices. It's the software that converts the code written by a website's designers into browsable text, pictures and dynamic content. Other web browsers are available for both iOS and Mac OS X, such as Chrome, Firefox and Opera, although Safari will always remain the default browser on an unjailbroken iPhone or iPad; this means any time you click a link on Twitter or Mail iOS will open the link in Safari, even if you normally browse the web in Dolphin.
What's a screenshot?
A contraction of screen and snapshot, this simply means a static image of whatever is on a screen at a given time. It's useful for showing error messages and glitches to tech-savvy friends, for showing off photogenic moments in games, and (if you run a website for Mac, iPhone and iPad users) for illustrating tech tutorials, apps and games.
You can take a screenshot on a Mac by pressing Shift, Cmd and 4 and dragging the cross over the area you want to capture, but there are a few other techniques - capturing individual windows, the entire screen and so on - explained in that linked article.
To capture a screenshot on an iPhone or iPad, you simply need to press the Power/sleep/wake button (the one at the top) and the Home button (the one below the screen) at the same time.
What is the Settings app?
A pre-installed app in iOS that enables you to adjust system-wide settings - such as changing the desktop wallpaper, switching Wi-Fi or data roaming on or off, or turning down the screen brightness - or specific settings for individual apps. A few of the most frequently used settings, such as the brightness, volume, Airplane Mode and Do Not Disturb, can also be accessed via the Control Centre.
The Settings app icon is the one that looks like a load of grey cogs.
What is the Sleep/Wake button?
The button at top of iOS devices that enables you to wake up the device, or put it back to sleep. If you hold it down you can power the device down completely. Sometimes also called the power button.
The sleep/wake button seems somewhat prone to malfunctioning, unfortunately, but if your iPhone's sleep button isn't working, there is a clever fix.
What's a SIM?
The little chip in a phone or (if you want to add 3G capabilities) tablet that contains your 'cellular identity'. Comes in various sizes, most commonly micro-SIM and nano-SIM. We talk about the differences between these, which type is needed for each iPhone and iPad, and how to insert them, in our tutorial How to put a SIM card into a new iPad.
What is Siri?
Voice-recognition technology featured in more recent iPhones and iPads. (The iPad 3 and later, and the iPhone 4S and later, get access to Siri if they've updated to the most recent version of iOS.) Enables you to perform many features on the device without having to interact with the touchscreen.
If you've been having trouble with Siri, take a look at our Siri troubleshooting guide.
What is Spotlight search?
Search technology found in iOS and Mac OS X devices that enables you to find many different types of information: contacts, documents, music files and so on. Can search through documents as well as by the file name.
What is a status bar?
The top bar running along the iOS devices. Displays many small icons related to the status of the device (Wi-Fi, Bluetooth, 3G and so on).
In this case, we can tell (reading from left to right): that the cellular signal is moderately strong (3 spots out of 5); that our carrier firm is 3; that we are connected to Wi-Fi, and that the Wi-Fi signal is strong (three bars out of three). Then on the righthand side of the screen: we are in Do Not Disturb mode (that's the moon symbol); we are using Bluetooth; that our battery is at 58% power (this is also indicated visually); and that we are currently charging the iPad.
For more information on all the symbols that can appear on an iPad or iPhone screen, take a look at our article 'What does it mean on an iPhone when…'
What is a tap?
As well as an item of bathroom plumbing, a tap is a gesture used on iOS whereby you quickly place and then remove a single finger on the screen. Comparable to a 'left-click' used on a desktop mouse or trackpad.
What is Time Capsule?
A device sold by Apple that combines a wireless router with a hard drive. Enables users to wirelessly backup Mac computers.
What is Time Machine?
Backup software made by Apple - be sure to back up your documents and files so you're not caught out when tech disaster strikes. We discuss how to get the most out of Time Machine in the following tutorials:
- How to back up a Mac using Time Machine
- How to create redundant Time Machine backups
- How do I restore my Mac with Time Machine?
- How to transfer a Time Machine backup to a new Mac
- How to transfer multiple Time Machine backups accounts to a single new Mac
What is a troll?
On the internet, this is a pejorative term that originally referred to forum users who were only interested in starting arguments.
These days people use the term troll more loosely, no longer distinguishing between those who are willing to argue to defend their (possibly extreme) views, and the original trolls who went out looking for arguments, sometimes pretending to have extreme views they didn't really believe in. Sometimes it seems to mean 'people I don't agree with'.
For Macworld's take on the concept, see our article Best (and worst) of the Android fanboys: Our 15 favourite troll comments.
Outside the internet, a troll is a large, ugly beast that may turn to stone when exposed to sunlight.
What is a UDID?
A UDID (which stands for unique device identifier) is a 40-character alphanumeric code allocated to every iPhone, iPad or iPod touch. If you've agreed to beta-test some pre-release software you may be asked for your UDID, which lets an app developer bypass the normal App Store download process.
What is a universal app?
If we're talking iPad and iPhone apps, this is simply an app that has been designed in such a way that a single app will run on both iPhone and iPad (and iPod touch and iPad mini, for that matter).
Some apps only work on iPad (and iPad mini) or iPhone (and iPod touch), whereas other developers write separate apps for each device. But a universal app works on them all (provided they are recent enough - the developers should specify which particular models the app is compatible with). If you buy a universal app on your iPad, you can download it to your iPhone at no extra cost. Universal apps are therefore A Good Thing.
We explain the finer points of universal apps in our tutorial - which also covers how to run iPhone apps on iPads, and how to run iPad apps on iPhones.
What is unlocking?
Phone unlocking is a process whereby you make it possible to use any SIM rather than just the one you received from your mobile provider.
Many people think iPhone unlocking is difficult, or illegal, and the suspect-looking shops that specialise in SIM card unlocking don't do much to suggest that iPhone unlocking is a legitimate practice. But you can get free iPhone unlock codes from your mobile phone operator.
What is Wi-Fi?
Wireless technology used to transmit data from a router to a mobile device (such as a laptop, smartphone or tablet).
What is Xcode?
Mac OS X software development environment. A program distributed for free by Apple that enables users to create Mac OS X and iOS software.