How Android Tablets Work

In the tablet market, there are two primary philosophies when it comes to device design. On one side you have the juggernaut: the Apple iPad. Apple has strict control over the entire design of the iPad from the user interface (UI) all the way down to the actual hardware. Every design decision comes from Apple itself. On the other side, you have Android tablets. While Google is responsible for the Android operating system (OS), other companies produce the hardware. Hardware manufacturers may even alter the UI without changing the functionality of the operating system. The bottom line is that if you look at two iPad 2 devices side by side, they'll essentially be identical. But pick any two Android tablets and you may notice some big differences. Google doesn't set standards for a tablet's size, weight or screen dimensions.

Which philosophy is better? That depends upon your own point of view. If you like sleek design aesthetics and an operating system that works in a clean, predictable way, the Apple iPad may appeal to you. But if you like to tweak settings and change things around, the Android approach may suit you best. In the end, both types of tablets will let you perform similar tasks on the go.

Another reason that defining an Android tablet is tricky is that you can find the Android operating system on numerous devices from many different manufacturers. Some of those devices run an older version of Android that isn't optimized for the tablet experience. These devices rely on versions of the OS before Android 3.0, so you'll get a tablet device running an operating system originally intended for a smartphone.

Once Google released Android 3.0, manufacturers like Motorola Mobility began to produce tablets with an optimized operating system. That means Google designed this build of the operating system with tablets in mind. Tablets running on Android 3.0 will have features and options you won't find on older tablets.

A device is really only as good as the applications it can run. Android owners may not have access to the sheer number of apps available to iOS owners -- at the time of this writing, the Apple App Store boasts more than 90,000 apps for the iPad and over 400,000 for iOS in general [source: Apple]. But Apple limits iPad owners to purchasing apps from the official App Store exclusively. With an Android device, you can install any app designed for Android whether you find it in the Android Market or elsewhere. You may have to change your device's settings to allow it to accept apps from unofficial sources but the freedom is there. But be warned; downloading apps from unofficial sources may be dangerous. You could download malware to your Android device.

It boils down to this: An Android tablet is a touch-screen, mobile device that runs some version of the Android operating system on it. And it's not a smartphone, though with the right software and hardware you might be able to make calls over Wi-Fi networks using one.

Next, we'll dive into the Android operating system and see what makes it tick.

The variety of Android tablets on the market make it difficult to sum up specifications. Android tablets are really just specialized computers. In general, most tablets contain the following hardware components:

Specific Android tablets may have other components or may lack some of the ones on this list.

All Android tablets run a version of Google's mobile operating system. Most of the latest Android tablets feature Honeycomb, also known as Android 3.0. Older tablets may be stuck with an operating system Google designed for smartphones. A few are in the tablet dark ages, running Android 1.5 -- also known as Cupcake. Older versions of the operating system may not be able to run some Android apps. The older the Android build, the fewer apps the tablet will be able to run without problems. Many Android tablets run some version of Android between Cupcake and Honeycomb.

All versions of Android have the same foundation. You can visualize the Android operating system as several layers. Computer engineers call this a software stack. Elements at the top of the stack are what the user sees while interacting with the operating system. The bottom of the stack includes the parts of the operating system that interface directly with the device's hardware.

Android's software stack begins with the hardware at the bottom. These are the physical components that make up the Android tablet device -- processors, sensors, wires and circuit boards. On top of this layer rests the kernel. An operating system kernel is sometimes called firmware -- software that controls, manages and allocates hardware resources so that the device does what you tell it to do. Google modeled Android's kernel after Linux 2.6, an open-source operating system.

On top of the kernel are Android's libraries. The libraries in Android are collections of instructions the device follows when processing different types of data. An example is the three-dimensional acceleration library, which contains all the instructions the Android device needs to interpret and respond to changes in the device's orientation and acceleration. Next to the Android libraries -- on the same level in the software stack -- you'll find the core libraries necessary to support applications written in Java. Java is a programming language from Sun Microsystems.

On the same layer as the libraries you'll find the Android virtual machine. This is a piece of software that creates a virtual operating environment. It acts just as if it were a physical device with its own operating system. Google designed this layer so that each application on Android runs as a single process. That way, should a process crash on you while you're in the middle of it, everything else remains unaffected. The virtual machine also acts as a memory manager.

The next layer up is the application framework. This is the foundation for all the apps on your Android device. The application framework acts as a liaison between Android apps and the rest of the operating system. Google outlines the guidelines to build apps that interact with this layer in the Android application programming interface (API). Developers only have to learn the rules set down by the API -- they don't need to worry about the hardware specifications of each Android tablet.

Finally, the top layer includes the user interface and all the apps on the Android tablet. This is the part of the operating system the average user sees. But underneath that flashy layer of animation and interaction is a lot of code!

Next, we'll look at what you should consider when buying an Android tablet.

Before you set out to buy an Android tablet, you need to ask yourself a few questions. Are you prepared for a device that has a learning curve? Navigating an Android device is a learning experience. Other operating systems may prove to be more intuitive, but you'll have a lot of flexibility with an Android device.

The next question to ask is how much are you willing to spend? Because there are dozens of different Android tablets from various manufacturers on the market, prices vary more than with Apple's iPad line. But the saying "you get what you pay for" comes into play -- less-expensive tablets may be made from cheaper materials and feature an older version of the Android operating system.

Researching the products is important. If you want a device that can run the latest apps and has all the features Android allows, you'll want to concentrate on the tablets with the most recent build of the Android operating system. Older Android tablets may not be able to run more advanced versions of the operating system, limiting your options.

Don't leave out a review of the hardware. Not all Android tablets are equal. If you want a tablet that lets you make video calls, you'll want one that has a forward-facing camera. If you plan to store a lot of content on your device, including movies, music and apps, you'll probably want a tablet with expandable storage like an SD-card slot. Will you want to use your Android tablet on the road? If so, you may want one with a cellular antenna so that you can access the Internet even if you're not near a Wi-Fi network. Keep in mind that you may have to subscribe to a cellular service plan to take advantage of this feature.

Android tablets come in different shapes and sizes. You'll need to decide which form factor best suits your needs. Do you want something really portable that can slip into an oversized pocket or a small bag? Do you prefer a device with a lot of screen real estate? If you plan to use your tablet to watch a lot of video content you may want one with a larger screen.

Make sure you read product reviews before you settle on any one device. Reviews might point out flaws in the hardware design or implementation. They might also give you more insight as to how you'd use the tablet. It's a good idea to get your reviews from several sources no matter what product you're considering to purchase.

The good news is that there are so many Android tablets on the market that one of them is bound to fit your needs. You just have to figure out what those needs are before you head out to the store.

To learn more about tablets and the Android operating system, follow the links on the next page.