Disk Operating System abbreviated as DOS is a product of Microsoft Corporation released in 1981 and it comes as part-and-parcel with Microsoft Windows operating system.
To get to DOS prompt and give commands for performing tasks on files and directories, Click Start > Run… and type command or cmd and press ENTER.
Windows is a series of most popular operating systems developed by Microsoft for use on personal computers. First edition of Windows that runs on MS-DOS 5.0 was released in 1985, as a 16-bit OS. Of all the editions of Windows OS released by Microsoft Corporation from 1985 till date, the popular ones include Windows 98, Windows 2000 Professional, Windows XP, Windows Vista and Windows 7. Read more on Evolution of Windows from hongkiat.com
Coming to differences, here are 5 basic ones that differentiate DOS and Windows: