When Bill Gates started to develop Windows he made the software information free to developers of software. Steve Jobs at Apple sold the OS software information. So, most software developers decided to make software just for Windows OS since it didn't cost anything. Additionally, Windows was the choice operating system on the PC line of products which was in the early '80s one of the most affordable personal computers of similar capabilities. This was combined with great marketing efforts on behalf of Microsoft. Also, Microsoft has won the battle for the most popular productivity suite with Office, and has more or less bundled Office with Windows ever since, enhancing the popularity of Windows too. Part of Microsoft's marketing effort has been directed not only at the end-user, but also at developers (by trying to motivate them to write software for windows instead of other OS's) and hardware vendors (motivating them to pre-install Windows on new PCs). All in all, Microsoft's aggressive and shrewd marketing and commercial strategies have been instrumental in securing an early lead for Windows. More recently, competition is more intense for Windows, but inertia plays a very large role in preserving Microsoft's lead, as people and corporations often experience significant difficulties in switching to new operating systems and different applications that come with them.