Developers want their software to get used. For this to happen, they need to target development at operating systems that enjoy a substantial market share. This is a moving target. Several of today's most popular operating systems did not exist 20 years ago. Others have been here for decades, but their purpose has shifted as computing hardware has taken on new forms. There is no guarantee that today's hot platforms will still be relevant five years from now. As a developer, you just have to place your bets. But it pays to know the odds. Below is a survey of today's most popular operating systems, based on data from the past few years.

Android

With respect to smartphones, there is no doubt: Android is far and away the most popular operating system for smartphones. Recent estimates place Android's market share at around 85%. Following Android is Apple's iOS, with most of the remaining market share. Other systems like Windows phone and BlackBerry have tiny fractions of the market.

Android was developed by Google. Android is open-source and it is based on a modified Linux kernel. Because Android is open-source, phone manufacturers worldwide can load Android on phones without paying a fee. But, of course, Google has a way to make money from Android. Android bundles Google products like Google Play, YouTube, and Chrome. Google earns money on these through advertising, sales commissions, and other mechanisms. The European Union actually forced Google to charge phone manufacturers a fee to bundle Google apps with Android, because giving them away was unfair to the competition! Google has made tons of money by giving things away. For this reason, any app developer has to think seriously about authoring for Android and featuring their app in the Google Play Store.

Apple

Apple has made even more tons of money than Google has, but they have done this through a completely different business model. Apple historically has been a hardware company. This legacy goes back to the Apple I and II personal computers of the late '70s and early '80s. It continued through the Macintosh. But Apple as a hardware giant really took off with its groundbreaking mobile devices of the 21st century. First came the iPod. Then the iPhone. Then the iPad. Each of these were category killers when they launched. Before the iPod, music downloading was essentially piracy-based. Apple created a viable, legitimate business model for online music downloads. When it launched in 2007, the iPhone likewise basically invented the modern touchscreen smartphone. [Before that time, BlackBerries with tiny physical keyboards were considered cutting edge.] Similarly, the iPad, featuring Apple's signature intuitive interface and tight software/hardware integration, set a performance standard that all other tablet manufacturers have had to chase. Apple commands premium prices for its hardware because of easy-to-use features and a sticky ecosystem of software and services that users come to rely on. Although Android has a larger market share, inconsistencies among different Android manufacturers, along with Apple's high-spending and dedicated user base, can make iOS an attractive target for app developers.

Speaking of iOS, Apple has used all sorts of different operating systems over the years and the OS names for different Apple devices vary one from the other. [Compare this to Microsoft for which the same "Windows" brand applies to pretty much everything.] First all, the iOS name is easy to understand — it goes with iPad, iPhone, iPod, etc. [You might say: "iGetIt!"] MacOS is Apple's current desktop operating system. An earlier version of macOS was called OS X ("OS Ten"). So, you really can't speak generically about Apple's operating system. It depends on the device and the generation. For current smartphone purposes, iOS is the one to focus on.

Windows and Cloud

When it comes to PC desktop operating systems, again — no contest. Despite its many detractors, Microsoft Windows continues to enjoy market share in the 75-85% range. In its heyday of the 1980s and 1990s, this would have been more like 95%. So, maybe Windows is slipping a bit. Still, if your goal is application development for a PC user base, Windows is impossible to ignore. The history of Windows versions is long, and for a different discussion in a different course. The current version is Windows 10. The competition comes from macOS, Linux and Google's Chromebook.

On the server side of things, Windows continues to enjoy a healthy, but not nearly so dominant, market share. One estimate puts Windows Server market share at about 48%. This may overstate the case, however, because when it comes to cloud and Internet-facing servers, by most accounts Linux is the most popular OS. Windows Server dominates in the more traditional on-premises business data center market. This market is fading, however, as cloud becomes the emerging leader for business computing. Amazon Web Services (running a highly customized version of Linux) is the industry leader in cloud. Microsoft also has grown a huge cloud computing business through its Azure service.

No Clear Winner

When it comes to sheer money-making potential, the stock market has a hard time deciding whether Microsoft, Amazon, Google, or Apple is the more valuable company. As of this writing, each of these firms is worth over 1 trillion dollars. As a software developer, you can enjoy a small taste of this very lucrative information technology industry. Which OS flavor should you choose to build software for? Well, that also is a matter of taste!

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