NEW YORK ( TheStreet) -- If you blinked over the past couple of quarters, you likely missed some very significant changes within the tech sector. But it should have come as no surprise as the market has been hinting at this shift for the past couple of years.It started with the proclaimed "death of the PC." While the PC is still broadly viable, it is fair to say that its once ubiquitous nature is on the decline. While it has taken 10 years to fully become a reality, there are a few companies that stand to benefit quite a bit from this ongoing shift, some more than others. Here are four of them. It goes without saying that Apple ( AAPL), which has contributed to the demise of the PC and sending names such as Hewlett-Packard ( HPQ) and Dell ( DELL) to the bin of the irrelevant, has to be at the top of the list. Its iPhones and iPads continue to lead a new wave of smartphone and mobile device proliferation that now includes Microsoft ( MSFT), Google ( GOOG) and presumably Amazon ( AMZN). However, Apple's most impressive accomplishment continues to be in markets it has yet to dominate. The company understands the only guarantee on Wall Street for market leaders is they don't remain market leaders forever. For this reason Apple continues to push the envelope while seeking to produce products that consumers have not yet realized that they can't live without. The result is what we are now witnessing where its rivals want nothing more than to put Apple out of business. The irony in all of this is that it means its rivals are also worthy investments. Take, for example, Microsoft, which has adopted a new business model where it has essentially said to its partners in HP and Dell it's every man for himself. What this means is the company is not only willing to change with the times, but it is willing to grow even if it means risking is current relationships. What this says to investors is that Microsoft has a considerable amount of confidence in its ability to enter new markets while preserving its existing market share in areas such as the enterprise and the home consumer markets.