How the iPhone Functions

In January 2007, Steve Jobs unveiled the Apple iPhone during his keynote at the Macworld Conference and Expo. The first time it appeared on screen, the phone resembled a sleek yet lifeless black rectangle in Jobs's hand.

Then, Jobs touched the screen. In an instant, the blank rectangle transformed into an interactive surface. Jobs tapped an on-screen arrow and slid it across the screen. As his finger moved, the arrow followed suit, unlocking the device. For many, the interaction between the finger and the screen was more astonishing than the iPhone’s other features combined.

And the features are abundant. In many respects, the iPhone is closer to a handheld computer than a traditional cell phone. Like most smartphones, it allows you to make calls, watch videos, enjoy music, surf the Web, and send and receive emails and text messages. It also lets you take photos and videos (on the iPhone 3GS or later models) with its built-in camera, import photos from your computer, and organize them using the iPhone's software.

In 2008, Apple unveiled the second-generation iPhone. This model operates on third-generation (3G) cellular networks and features a GPS receiver. It also allows users to access map and satellite data through Google Maps, including business overlays nearby. Original iPhone owners were given the chance to upgrade their devices with new software. The 2.0 update added new capabilities, though it did not include the GPS receiver or 3G network support.

In 2009, Apple launched the iPhone 3GS, a model with more storage capacity than its predecessors. It also introduced a superior camera, capable of capturing still images and video at 30 frames per second. The addition of a compass helped users navigate unfamiliar areas. Additionally, iPhone OS 3.0 was released, offering significant improvements, such as the long-awaited cut and paste functionality.

In 2010, Steve Jobs took the stage to announce a new iPhone generation: the iPhone 4. The iPhone 4 comes equipped with two cameras, one front-facing and one rear-facing. It also features a retina display with higher resolution than its predecessors, and marked a departure from the previous design with a flat back, unlike the slightly curved back of older models. Jobs also revealed a new name for the iPhone’s operating system: iOS, a customized version of the Macintosh OS X operating system used on Apple desktop and laptop computers.

The iPhone 5 was released in the third quarter of 2013, offering consumers two different models to choose from. The iPhone 5s features an A7 64-bit chip and introduces an added layer of security with a fingerprint identity sensor (though debates about its level of security have emerged). The iPhone 5c is a more affordable option, with plastic casings available in a variety of colors.

Apple's iOS enables interaction with all apps on the iPhone. It displays icons for each app on the device's screen and manages battery life and system security. For older iPhones and iOS versions, the operating system syncs the device with a computer using a connector similar to the one used with iPods, but since iOS 5, syncing across Apple devices can be done via the iCloud service. iOS also allows multitasking and seamless navigation through multiple open apps, much like on a laptop or desktop computer.

Instead of relying on a mouse or physical keyboard, the iPhone uses virtual buttons and controls that appear directly on its screen. This isn't a novel concept -- touch screens have been utilized in devices like self-checkout kiosks and smartphones for years. However, the iPhone’s touch screen is unique compared to others on the market. While a PDA or a Nintendo DS typically requires a slender, pointed stylus, the iPhone only needs your fingers or a conductive stylus. It can even detect multiple touch points at once.

This article will dive into how the iPhone's touch screen transmits your touch commands to the device's internal circuitry. Additionally, we’ll explore the features of Apple's latest models, the iPhone 5c and 5s, as well as the 2013 update to its operating system, iOS 7.

iPhone Touch Screen

Electronic devices can employ various techniques to detect input on a touch screen. Many use sensors and circuitry to detect changes in a particular state. The iPhone, for example, monitors shifts in electrical current. Other devices track changes in the reflection of waves, whether sound waves or near-infrared light beams. Some systems also use transducers to measure vibrations when your finger taps the screen, or employ cameras to observe changes in light and shadow.

The concept is quite simple -- when you touch the screen with your finger or a stylus, it alters the state that the device is monitoring. In screens that work with sound or light waves, your finger either blocks or reflects part of the waves. Capacitive touch screens feature a layer of capacitive material that holds an electrical charge; when you touch the screen, the charge at the point of contact changes. On the other hand, resistive screens detect the pressure from your finger, causing conductive and resistive layers to touch, which alters the circuit’s resistance.

Usually, these systems excel at detecting the location of a single touch. However, if you attempt to touch multiple places on the screen simultaneously, the results can be inconsistent. Some screens ignore all touches beyond the first one, while others can detect multiple touches but struggle to accurately calculate their locations. There are several factors that contribute to this issue, including the following:

Many systems detect changes along a specific axis or direction instead of pinpointing each location on the screen. Some rely on system-wide averages to estimate touch positions, while others take measurements by first establishing a baseline. When you touch the screen, a new baseline is created, and adding another touch can cause the system to measure using an incorrect starting point.

The Apple iPhone stands out in this regard -- many features of its multi-touch interface require you to touch multiple points simultaneously. For instance, you can zoom in on Web pages or images by placing your thumb and finger on the screen and spreading them apart. To zoom out, you can pinch your thumb and finger together. The iPhone’s touch screen can detect both touch points and their movements at the same time. In the next section, we'll explore how the iPhone accomplishes this.

Multi-touch Systems

In order to enable multi-finger touch commands, the iPhone utilizes a unique arrangement of existing technologies. The screen incorporates a layer of capacitive material, similar to many other touch screens. However, the iPhone's capacitors are organized in a grid-like system. The device's circuitry can detect changes at each point in this grid. In other words, each point generates a signal when touched and transmits it to the iPhone's processor. This enables the phone to track the location and movement of multiple simultaneous touches. Because of this capacitive setup, the iPhone only responds to fingertip contact -- it won't work with a stylus or when you're wearing non-conductive gloves.

The iPhone screen detects touch using one of two methods: Mutual capacitance or self capacitance. In mutual capacitance, the system uses two layers of material: one for driving lines that carry current and another for sensing lines that detect current at specific nodes. Self capacitance, on the other hand, uses a single layer of individual electrodes connected to capacitance-sensing circuitry. Both setups transmit touch information as electrical signals.

The 2012 iPhone 5 introduced a new in-cell touch screen, which maintains the capacitive multi-touch technology but integrates the capacitive touch sensing layer with the LCD display layer into one single component.

iPhone Processor Touch Interpretation

The iPhone's processor and its software play a crucial role in interpreting the input from the touch screen. When you touch the screen, the capacitive material sends the touch location data to the processor. The processor then utilizes software stored in the iPhone's memory to convert this raw data into commands and gestures. Here's how the process works:

1. The touch screen sends signals to the processor in the form of electrical impulses.

2. The processor uses the software to interpret the data and determine the characteristics of each touch, such as the size, shape, and location of the touch area. If necessary, the processor groups touches that share similar characteristics. When you move your finger, the processor calculates the difference between the start and end points of your touch.

3. The processor uses its gesture-interpretation software to recognize the gesture you made. It combines your finger movement with context, such as the app you're using and its state when you touched the screen.

4. The processor sends your instructions to the active program. If needed, it also communicates with the iPhone's display and other hardware components. If the raw data doesn't correspond to any recognized gestures or commands, the iPhone dismisses it as an unnecessary touch.

All of this happens in the blink of an eye – you see the screen respond to your input nearly instantaneously. This rapid process enables you to interact with the iPhone’s apps using just your fingers. In the next section, we'll explore these apps, the iPhone’s other features, and how its price compares to its capabilities.

iPhone Features

The front of the Apple iPhone features just one button – the Home button. Pressing this button takes you to the main screen of the iPhone's graphical user interface, where you'll find the pre-installed Apple apps. You can switch between pages and discover more apps by simply swiping from one side to the other. From any screen, you can also access four primary functions using the icons at the bottom. By default, these are:

You can swap out other apps into the bottom row by pressing and holding any app icon until they begin to shake. Then you can slide one app into place on the main screen and replace it with something else in the bottom area.

The iPhone's other applications can be accessed from the top part of the Home screen. These include a calendar, a calculator, a notepad, and widgets, which are mini-apps designed specifically for the iPhone. Older iPhones feature a 2.0- or 3.2-megapixel camera with software for organizing your photos, while the iPhone 5s boasts an 8-megapixel camera. You can also use your iPhone to check weather updates and stock quotes. Although the iPhone doesn’t support Flash (which is needed for YouTube's non-mobile site), you can still watch YouTube videos via the YouTube app. Prior to iOS 6, YouTube was built into the system. Now, the iOS requires you to download the Google YouTube app or any other app that can access YouTube content. Virtual keys and buttons for navigating apps only appear when they’re needed.

The screen also changes its shape as necessary – you can switch from vertical to horizontal by simply tilting the phone. An internal accelerometer tells the system to adjust the screen orientation. This allows you to scroll through long lists of music on a narrow screen, and enjoy movies in a widescreen format. To learn more about accelerometers, check out How the Wii Works.

In addition to the Home button, the iPhone has several other physical buttons and switches around its edges. The power or sleep button is located at the top of the device. On the left side, a switch allows you to toggle the phone between ringing and silent modes. Just below this switch are the volume control buttons.

The iPhone's second generation brought along a number of exciting new features. We'll dive into these updates in the following section.

3G iPhone Applications and Problems

In June 2008, Steve Jobs unveiled the 3G iPhone at an application developer conference. Apple offered both 8 GB and 16 GB versions of this iPhone model. The design of the phone remained mostly the same, but it had a slightly more streamlined look, and the back was no longer silver. The 16 GB model was available with a black or white plastic back, while the 8 GB version was only offered in black.

One of the major announcements, aside from the phone's ability to tap into 3G network technology, was the inclusion of a GPS receiver in the 3G iPhone. A common issue with GPS devices is their tendency to quickly drain battery life because they are continuously receiving signals from orbiting satellites.

Another significant enhancement in the 3G iPhone was the support for Microsoft Exchange. With this addition, users were now able to sync their iPhones with their Microsoft Outlook accounts. By incorporating this feature, the iPhone became a stronger competitor against other enterprise smartphones, which businesses rely on to keep their workforce connected while on the go.

When the first iPhone was launched, Apple did not support third-party applications, although developers still found ways to create them. However, running a non-Apple app on the original iPhone required 'jailbreaking' the device. Jailbreaking allowed users to install third-party applications, but it came with risks -- attempting to install official Apple updates on a jailbroken phone could result in Apple detecting the modification. With the 3G iPhone, however, Apple embraced third-party apps and encouraged developers to create content for the device.

The launch of the 3G iPhone didn't go smoothly. Instead of allowing customers to buy and activate their phones at home, Apple required them to activate in-store. Unfortunately, the company's systems were overwhelmed, leading to significant delays during the product launch. As a result, most customers had to activate their phones at home anyway.

Some of the new applications available after Apple opened development for the iPhone took advantage of the device's built-in accelerometer. Games like 'Super MonkeyBall' enabled players to control the character by tilting the phone in different directions. Could the iPhone become the next portable gaming platform? That's exactly what Apple predicted at their September 9, 2009 press event, setting the stage for the iPhone 3GS.

iPhone 3GS

At the 2009 World Wide Developers Conference (WWDC), Apple introduced the iPhone 3GS. The 'S' stands for 'speed,' and according to Apple, this new iPhone is up to twice as fast as the previous 3G model, both in terms of data access and app launches. In testing, journalists found that the iPhone 3GS was better at picking up 3G signals from carriers compared to its predecessor.

The iPhone 3GS isn't just faster than previous models; it also introduces a range of new features. Here’s a summary of what you’ll find on the iPhone 3GS:

While these features were promoted as groundbreaking innovations, many of them had already been available on other smartphones.

On the following page, we will explore the iPhone 4 in more detail.

iPhone 4

In 2010, Steve Jobs revealed the iPhone 4, confirming many of the rumors that had been circulating for weeks. The technology blog Gizmodo made waves by publishing a story about a prototype iPhone 4, which had been accidentally left behind at a bar by an Apple employee. Although Apple had remotely locked most of its functions, Gizmodo was able to uncover many of its features.

Jobs subtly acknowledged that his audience was already familiar with much of the phone’s details, but still had some surprises in store. The iPhone 4 introduced a new design, replacing the curved back with flat surfaces. It also came with two cameras: the rear-facing camera offered 5-megapixel photos and 720p video recording, along with an LED flash for better low-light shots. The front-facing camera enabled Apple's Facetime app, allowing video calls between other iPhone 4 users, compatible iPod touch devices, and Mac OS X users.

Both the front and back of the phone are encased in glass, with metal bands surrounding the edges that also serve as antennae.

The iPhone 4 features what Apple refers to as a retina display. With a resolution of 960 by 640 pixels, or 326 pixels per inch, it offers an 800:1 contrast ratio.

Additional features of the iPhone 4 include:

One year after launching the iPhone 4, Apple took the stage at its annual WWDC event, not to announce a new phone, but to reveal the next version of its mobile operating system, iOS, which came with several significant upgrades.

iOS 5

In June 2011, Apple introduced iOS 5.0, its latest mobile operating system, several months before the release of the iPhone 4S, the device it was designed to accompany. The OS went through months of beta testing before it was made available for iPhones, iPads, and iPod touches. iOS 5 was one of the most significant updates in the iPhone’s history. The most notable feature was Siri, a personal assistant built directly into the system. Siri is only available on the iPhone 4S and newer models. While iOS 5 can be installed on the iPhone 4 and iPhone 3GS, Siri is not compatible with these devices.

Siri uses natural language processing to understand spoken commands. When you speak to Siri, your voice is sent to a server, processed, and then the response is returned to your phone, typically in just a few seconds. Siri can perform tasks like sending messages, setting alarms, appointments, and reminders, finding restaurants, or making voice calls. By filling in contact information, Siri can handle commands like “Call my wife” or “Remind me to take my keys when I leave the office.”

Apple also revamped the notification system for all iOS 5 users, borrowing elements from Android’s convenient sliding tray. Notifications no longer disrupt your app by appearing in the middle of the screen; instead, they are housed in a tray that slides down from the top with a simple swipe. Other new features include:

iPhone 4S

Steve Jobs passed away on October 5, 2011, just one day after Tim Cook, his chosen successor, took the stage at the annual fall Apple event to introduce the iPhone 4S. This event marked the first time Jobs wasn’t the one presenting the new iPhone, though his legacy was evident in the device. Until the event began, many had speculated that Apple would release the iPhone 5, alongside a cheaper version of the iPhone 4 dubbed the iPhone 4S. However, this didn’t come to fruition. Much like the iPhone 3GS, the iPhone 4S maintained the same body design as the iPhone 4, with substantial improvements to its internal components.

The iPhone 4S brought three key updates: enhanced processing power with a dual-core CPU and GPU; improved photography with an 8-megapixel camera; and integrated voice control through Siri, the voice assistant we discussed in the iOS 5 section. While iOS 5 is available for free on the iPhone 3GS and iPhone 4, Siri is exclusive to the iPhone 4S and later models.

Apple powered the iPhone 4S with the same 1GHz A5 system-on-a-chip found in the iPad 2. The A5 chip features dual-core CPU and GPU processing, making the iPhone 4S much faster than the iPhone 4's A4 chip. In performance-intensive tasks like Javascript execution and graphics-heavy games, the iPhone 4S outperformed all Android devices available in fall 2011. For example, in the GLBenchmark 2.1 test, the iPhone 4S scored 122 frames per second, while the Samsung Galaxy S II reached 67, and the iPhone 4 only managed 15 [source: Anandtech].

The iPhone 4S camera received a significant boost, going from 5 megapixels to 8 megapixels. However, it’s not just the resolution that makes the camera better -- it’s the upgraded, larger sensor that captures 73% more light compared to the iPhone 4’s sensor. This improvement in light sensitivity is crucial for low-light photography. Apple also upgraded the lens, moving from a four-element system to a five-element system to sharpen the image, and enhanced the aperture from f/2.8 to f/2.4 for better light capture [source: Tested]. Additionally, the camera now supports 1080p video recording, a jump from the iPhone 4's 720p capability.

The iPhone 4S represented a significant milestone for Apple’s smartphone business, launching in October 2011 across AT&T, Sprint, and Verizon. It was the first iPhone to be compatible with both GSM and CDMA networks, the two primary cellular technologies worldwide. These dual-radio phones, known as 'worldphones,' offer global connectivity. However, there’s an important detail: only an unlocked iPhone 4S, priced at $650 through Apple, can use SIM cards in international locations.

iPhone 5

On September 12, 2012, Apple CEO Tim Cook led the company's fall special event and revealed the iPhone 5. This model underwent a significant redesign, with Apple optimizing the size of internal components to fit them more compactly. The iPhone 5 is thinner and lighter than earlier models, maintaining the same width but extending the length to accommodate a larger screen. Its dimensions are 7.6 mm (0.30 inches) in depth, 58.6 mm (2.31 inches) in width, 123.8 mm (4.87 inches) in height, and it weighs just 112 grams (3.95 ounces), making it 20% lighter than the 4S. The body is crafted from anodized aluminum with ceramic glass inserts.

The new iPhone features a retina display with a pixel density of 326 pixels per inch, just like the iPhone 4S. However, the screen size has grown from inches to 4 inches (8.9 cm to 10.2 cm) diagonally. This change increased the resolution from 960 by 640 pixels to 1136 by 640 pixels. The updated resolution gives the display a nearly 16:9 aspect ratio, allowing for widescreen HD video without letterboxing and offering more space for websites, email, games, and other applications. New apps are being designed to take advantage of this larger screen, though older apps will still work by leaving black borders on either side. This upgrade also adds an extra row of apps while keeping the width the same for a comfortable fit in your hand.

The iPhone 5's display now integrates touch sensors directly into the screen, eliminating the need for a separate touch layer. This results in a single-layer display where the pixels themselves act as touch-sensing electrodes. While there are now two chips controlling the touchscreen instead of one, the multi-touch capabilities remain unchanged. This design change makes the phone thinner, reduces glare, and enhances image sharpness.

The iPhone 5 is powered by a new processor, the A6, which is Apple's first fully in-house designed chip. Both the CPU and graphics performance are faster than the A5, with the A6 being nearly twice as fast for most tasks while maintaining or even reducing battery usage. This efficiency is enhanced by the new iOS 6 operating system (which will be covered in the next section). The improvements lead to faster app load times, quicker photo capture, smoother internet browsing, and better gaming performance.

The iPhone 5 supports a broader range of cellular networks than previous models, now including HSPA+, DC-HSDPA, and the latest ultra-fast LTE technology (with download speeds of up to 100 Mbps). A new single chip for voice and data, along with a dynamic antenna, enables seamless switching between networks. It also supports more WiFi standards than before: WiFi is now 802.11 a/b/g/n, with dual-channel 5GHz 802.11n and a maximum download speed of 150 Mbps, though this is a theoretical peak [source: Cook].

Both the iSight rear camera and the FaceTime front camera have received significant upgrades. The iSight camera now features a sapphire crystal lens, which is almost as hard as diamond and resistant to scratches. The lens alignment has been improved, and a new dynamic low-light mode enhances performance in dim environments. The FaceTime camera now supports 720p HD video, with backside illumination for better image quality. Additionally, the iPhone 5 includes three microphones – located on the bottom, front, and back – to improve audio quality through noise cancellation and beamforming.

The classic 30-pin connector has been replaced by Apple's new Lightning connector, which is 80% smaller in size. While this change means many older accessories are only compatible with the 30-pin connector, there's a solution: a Lightning-to-30-pin adapter is available for purchase. Plus, the new Lightning connector is reversible, so no more frustrating moments of flipping the connector over to insert it correctly.

Instead of the usual EarBuds, the iPhone 5 comes with newly designed EarPods. These EarPods are said to offer better sound quality and a more comfortable fit for a wider variety of ear shapes compared to the previous model.

During its first weekend of release, the iPhone 5 sold about 5 million units, shattering the sales records set by the iPhone 4S [sources: Satariano, Martin].

Keep reading to learn more about the new version of iOS that was introduced alongside the iPhone 5.

iPhone 5s and 5c

On September 10, 2013, Apple revealed the iPhone 5s and iPhone 5c. The 5s is a completely new model with upgraded hardware and features, while the 5c is a more affordable version with only minor changes to the iPhone 5.

The iPhone 5c is positioned as a budget-friendly option. With a two-year contract, the 16GB model debuted at $99 in the U.S., while the 32GB version cost $100 more. One of its main selling points is its colorful plastic casing, available in five shades. Despite the colors, the internal components remain identical to the iPhone 5.

The 5c's battery and antennas differ from the iPhone 5. The 5c has a higher capacity battery, providing a longer-lasting charge. Additionally, its antennas are designed to support a wider range of global frequencies than any other smartphone.

While the iPhone 5c received attention, the real spotlight was on the iPhone 5s, which introduced major hardware upgrades.

Apple revamped the classic home button by incorporating a fingerprint sensor. After registering your fingerprint, a simple tap unlocks the phone, authorizes purchases, and completes other security-sensitive actions.

This feature, known as TouchID, utilizes a sensor capable of reading sub-surface skin layers with a resolution of 500 pixels per inch, from any angle. Multiple fingerprints can be registered, allowing several people to access secure functions. While it was seen as a major advancement in security, a computer club managed to bypass the system shortly after the device’s release [source: Diaz].

Instead of the A6 chip, the 5s is equipped with the A7 processor, the first 64-bit processor ever to be used in a smartphone. Apps optimized for 64-bit should run more quickly and efficiently thanks to the new chip.

The 5s also features the M7 chip, a secondary processor designed to handle signals from the phone's accelerometer and gyroscopes. This chip helps reduce the processing burden on the A7 chip.

The 5s camera, like its predecessor, boasts 8 megapixels, but with enhanced features. It now has two LED flashes, one white and one amber, which are automatically chosen based on ambient lighting to ensure better color balance. Other improvements include a wider aperture (f/2.2), slow-motion video, a 10-frames-per-second burst mode, and image stabilization.

Both the 5c and 5s come preloaded with iOS 7, Apple's latest mobile operating system. On the following page, you'll discover all the new features that iOS has to offer.

iOS 7

Some early reviewers criticized the new iPhones for feeling somewhat stale in terms of hardware. However, iOS 7 introduces a series of significant changes that will certainly give Apple users plenty to explore.

The most striking change is the revamped visual interface, marking the largest redesign of iOS since its inception in 2007. iOS 7 ditches the elaborate graphical embellishments of previous versions, such as the faux leather and wood textures in the calendar and Newsstand apps, replacing them with a sleeker, more minimalistic look. You'll notice new icons, fonts, transparency effects, and enhanced graphical physics that give the interface a more three-dimensional feel.

iOS 7 showcases the eye-catching live wallpapers, which display on-screen bubbles that float in different directions depending on the phone's orientation.

Beyond the visual enhancements, there are several functional updates to iOS. One of the standout features is the revamped Control Center, accessible with a simple swipe-up gesture. This provides instant access to wireless settings, screen brightness, flashlight, airplane mode, and music controls.

The expanding App Store, now with nearly 900,000 apps, has improved its search functions. You can now filter apps based on popularity in your area or by their age-appropriateness, a welcome feature for parents. Additionally, apps can now update automatically in the background, eliminating the need for manual updates.

iOS 7 integrates seamlessly with iTunes and various cloud-based services. Now, instead of relying solely on locally stored tracks, you can access music from iCloud. It also introduces a long-awaited feature: the ability to create Pandora-like radio stations based on specific artists and songs.

Safari, Apple's web browser, now features a combined URL and search text box. This allows you to either type in a web address directly or initiate an Internet search, a feature that other phones have had for a while but is new to iOS. Safari also lets you open as many tabs as needed and swipe them away when you're done browsing.

Siri, the voice-command assistant, has gained some new abilities. Now you can simply say commands like 'increase screen brightness' or 'turn on WiFi,' and Siri will execute them right away. You can also choose from a variety of new voices and languages for Siri.

This version of iOS is also set to integrate with many car systems. In 2014, several automakers will offer displays that sync directly with the iPhone. With a simple voice command, the car will read messages to you (and allow you to respond), let you control the music system, and manage navigation functions.

AirDrop is now a built-in feature of the OS. With AirDrop, you can use your iPhone to effortlessly share files with other Apple devices via a WiFi connection.

The Camera app now offers live previews of various creative filters, allowing you to see how your photos will look in real-time. You can also swipe between different frame shapes like panoramic or square.

iOS includes a host of smaller updates, each designed to make this powerful device easier to use. Later, you'll discover how the latest iPhone compares to its competitors.

iPhone Competitors and the Evolving Smartphone Market

The iPhone 4S shattered records, becoming Apple's fastest-selling device with over 4 million units sold during its debut weekend [source: CNET]. The iPhone 5 outpaced that, selling about 5 million units in its opening weekend.

The iPhone 5c and 5s further propelled Apple to new heights, with an astounding 9 million units sold in just three days, marking these versions as the most successful iPhones to date. The surge in sales was partly driven by the inclusion of the Chinese market in the launch [Source: Reuters].

Though the iPhone dominates media coverage, other smartphones have adopted similar features. As of late 2013, Android, developed by Google, led the smartphone OS market with a 80% share, compared to Apple's 17% [source: Fox News].

However, Android's market share is divided among many different devices and manufacturers, while Apple enjoys exclusive profits from iPhone sales. Apple's strategy has always focused on maximizing profit margins rather than expanding market share.

The iPhone revolutionized the phone industry. Though 'smartphones' existed prior, Apple's emphasis on touch controls steered the entire market in a new direction. The once-popular Windows Phone 6.x was replaced by Windows Phone 7, and RIM's BlackBerry has been in steady decline. Android, with its open-source OS, now represents Apple's most significant competition, embraced by a range of electronics manufacturers.

The iPhone Carrier Spread in the U.S.

Apple introduced its first CDMA iPhone to U.S. users in early 2011 with the release of the iPhone 4 on Verizon's network. The iPhone 4S later featured a dual-mode chipset, allowing compatibility with Verizon and Sprint's CDMA networks as well as AT&T's GSM network. This enabled international roaming, though the phone remains locked to a specific carrier. To use it abroad, users must either buy an unlocked model directly from Apple (at a premium) or pay for a global roaming plan from a carrier.

With the iPhone 5s, Apple released four different models: A1533, A1453, A1457, and A1530, along with four versions of the 5c. Each model supports a variety of radio bands, with Apple incorporating as many as possible into each version to minimize the number of models it needs to produce and manage.

As of fall 2013, no single carrier offers a clear-cut best option. Sprint provides an unlimited data plan, while Verizon now offers limited data share plans that allow customers to share a fixed amount of data across multiple devices. AT&T also forces new customers into similar limited data mobile share plans, but allows older iPhone customers to keep their unlimited plan if they visit a retail store and request this option, instead of ordering online.

Carrier voice plans for the iPhone vary widely in terms of pricing and available minutes. Verizon and AT&T, being larger networks, may offer better cellular coverage depending on the region. Sprint and Verizon's CDMA technology prevents simultaneous voice and data use, while the latest iPhone supports faster HSPA+ data on AT&T's GSM network. In practice, data speeds can differ based on network usage and location, meaning Verizon or Sprint may outperform AT&T in certain areas. All carriers are working on faster LTE networks, but these are limited to certain locations, and only the iPhone 5 can fully utilize LTE. When choosing a carrier, plan, and phone, you'll need to consider multiple factors.