This article was originally published on June 9, 2015. It was updated on Jan. 12, 2016.

Much has been made in regard to the death of the PC. Yet even as the personal computing market contracts, it remains a massive global industry representing nearly $300 billion in revenue. And while some of the old guard leaders of yesteryear are struggling with stagnating and even declining sales, others, such as Microsoft (NASDAQ: MSFT), have found ways to adapt with aggressive new strategies. In addition, challengers such as Apple (NASDAQ: AAPL) and Alphabet (NASDAQ: GOOG) (NASDAQ: GOOGL) are rapidly taking share and emerging as the new titans of personal computing. Read on to see why these three tech giants are the best stocks to buy in the personal computing industry.

Source: Microsoft.

Long a force in the personal computing arena due to the dominance of its Windows operating system and Office productivity software, Microsoft now finds itself in a ferocious battle to defend its market share from fierce competition from Apple and Google.

As Windows dominance has waned due to the growth of Apple's Mac OS and Google's Chrome OS, new CEO Satya Nadella has taken steps to fortify Microsoft's Office franchise by making it available on non-Windows mobile devices. In this way, Nadella sacrificed the key advantage of Windows-based computers – full Office functionality – in order to protect and grow Microsoft's Office business. It was a wise decision that reflects Nadella's vision of moving Microsoft toward a mobile- and cloud-based future.

Microsoft, however, did not stop there.

With its Surface line of tablet computers, Microsoft is now competing more directly with Apple and Google by integrating its Windows OS and Office suite into Microsoft-designed hardware. It was a bold move, as it risked alienating Microsoft's OEM partners. Yet the gamble appears to be paying off; the Surface Pro 3 was Microsoft's best-selling "two-in-one" device ever, and the new Surface Pro 4 and Surface Book are off to strong start with positive early reviews.

As my colleague Leo Sun explains, the Surface Pro line seems to be filling the need for devices that help to bridge the gap between PCs and tablets. And even if the move by Microsoft to enter the hardware space did anger some of its partners, strong Surface sales have spurred them to create Surface-like devices of their own.

In fact, thanks in part to the success of the Surface, research firm IDC expects sales of Windows tablets and two-in-one devices to surge 41% year over year in 2015. Even better, IDC projects that Windows-powered devices will double their share of the global tablet market in the next five years, from 7% in 2015 to 14% by 2019. 

The mobile computing arena is an important battleground for Microsoft. And with IDC forecasting that annual tablet shipments will rise 17% between 2014 and 2019, while PC shipments are expected to fall 5% over that time, gaining a beachhead in this market should only grow in importance in the years ahead.

Source: Apple.

One company that's bucking the trend of declining PC sales is Apple. During the fourth quarter, Mac unit sales rose 3% year-over-year to 5.7 million – an impressive feat as it occurred during a time when the PC market contracted by 11% as estimated by IDC.

Even more impressive are Apple's longer-term market share gains; Macs unit sales have grown faster than the overall PC market for 37 out of the last 38 quarters. That's an remarkable streak that I expect to continue for the foreseeable future, with recent updates to Apple's popular iMac and MacBook computer lines likely to drive growth in the coming quarters.

Further fueling Apple's growth is the strong demand for its computers in China, a region where Apple's revenue surged 99% year-over-year in the fourth quarter. 

With surging growth in the massive Chinese market and a still less than 10% share of the global PC market, expect continued share gains for Apple in the years ahead.

A student at Urban Promise Academy uses a Chromebook to design video games. Source: Google.

Although Apple's overall sales have been strong, one area where we're beginning to see some cracks in Apple's armor is in the education segment. With budgetary struggles seemingly a never-ending saga for many schools across the U.S. and across the world, the cost advantages of Google's Chromebooks relative to Apple's Macs (and greater functionality compared to iPads) will likely continue to drive educational sales Google's way. In fact, a recent report by Gartner noted that the education market represented 72% of worldwide Chromebook sales in 2014, and that global Chromebook sales likely jumped 27% to 7.3 million units in 2015. 

This is a battle I will be watching closely, for if Apple is not careful, it could see Google disrupt its Mac business by taking share first at the low end of the market and then moving up the value chain with more feature-rich yet relatively less expensive computers.

For now, it's more likely that much of Google's overall share gains in the PC market will come at the expense of Windows-powered machines. But the education segment has been a major stronghold for Apple in recent years, and the rapid increase in Google's market share in this important area could be a worrisome sign of things to come for Apple and other PC competitors. Regardless, one thing is for sure: Google is quickly becoming a force to be reckoned with in the global PC market.

Suzanne Frey, an executive at Alphabet, is a member of The Motley Fool's board of directors. Joe Tenebruso has no position in any stocks mentioned. The Motley Fool owns shares of and recommends Alphabet (A shares), Alphabet (C shares), and Apple. Try any of our Foolish newsletter services free for 30 days. We Fools may not all hold the same opinions, but we all believe that considering a diverse range of insights makes us better investors. The Motley Fool has a disclosure policy.