What product did Microsoft publish the first version of in 1985?

Explanation

Microsoft Corporation was founded by Bill Gates and Paul Allen in 1975. It was then the operating system DOS, which became the start of the company's great progress. In 1981, Microsoft signed a contract with IBM to provide an operating system for their upcoming product, which was the first PC. In 1985, Microsoft released its first version of Microsoft Windows, and four years later, the company launched its flagship in the form of office suite, Microsoft Office.