For decades, Microsoft has made the software that runs a majority of the world’s personal computers, leaving a gang of outside hardware companies to design the machines. Apple, its rival, makes it all.

Microsoft is about to concede that Apple may be onto something.

On Monday, Microsoft is expected to introduce a tablet computer of its own design that runs a new version of its Windows operating system, according to people with knowledge of Microsoft’s plans who declined to be identified discussing confidential matters. It is the first time in the company’s 37-year history that it will offer a computer of its own creation. The device is aimed squarely at Apple’s blockbuster iPad, which has begun to threaten Microsoft’s hegemony in the computer business.

Microsoft’s move is another example of how Apple has demonstrated that the most effective way to create easy-to-use consumer gadgets is by building the whole package — upending the longstanding practice in the technology industry of companies’ devoting their energies to either hardware or software. Google, too, has made a big concession to Apple’s approach, signaling with its acquisition of Motorola Mobility last year that it will also design its own devices.

Frank Shaw, a Microsoft spokesman, declined to comment.

For Microsoft, the decision to make its own tablet would once have been almost unthinkable. Microsoft swallowed the PC market in the 1980s and 1990s by letting any hardware maker pay licensing fees to put Windows on its machines. That business was so lucrative for Microsoft that there was no reason for the company to make its own PCs and compete for computer sales with its own partners.