DOS, Disk Operating System. It was the original operating system that ran on PC s. Originally, DOS was developed by Microsoft for IBM s PCs.

Among all the operating systems of the DOS series, the most popular and the most used remains the MS-DOS. (MS means Microsoft).

With this kind of operating systems you type in the commands instead of pointing and clicking.

DOS can still run on Windows 95/98 but not on later operating systems developed by Microsoft.