This was the standard, most common operating system before Windows arrived. Basically, DOS is just a piece of software that manages how files are stored on the disk. It keeps track of where the files are stored, how big they are, and when they were created. It also provides time and date functions, together with the ability to start other software programs. DOS is controlled through a command-line interface, which means that you have to type in words to get it to do something. For example, if you want to see the files stored on a disk, type DIR (short for directory). DOS is flexible and quick, but is difficult for beginners to use because it's not in the least bit friendly. Windows changes all this by getting rid of the command-line interface and providing a graphical user interface in which you control actions by pointing and clicking with a mouse - there's no need to learn or type in command words. (See also MS-DOS.)
