Microsoft was founded in 1975.
Bill Gates and Paul Allen established Microsoft on April 4, 1975. The company initially developed and sold software for the Altair 8800, an early personal computer. Its early success helped establish software as a major commercial part of the personal-computing industry.
Microsoft later became closely associated with MS-DOS and Windows, which became dominant operating systems for personal computers. It expanded into productivity software, servers, gaming through Xbox, cloud computing through Azure, and business services.
The company’s market capitalization reflects the value investors place on all those businesses, not merely on Windows. Market cap is also separate from revenue and profit: it is the market price of one share multiplied by the total number of shares outstanding. Microsoft has repeatedly ranked among the world’s most valuable listed companies as its businesses and share price have grown.