DOS (Disk Operating System) is an operating system (like Windows or macOS) that was once used to run computers. It was popular in the 1980s and 1990s, but was eventually replaced by other operating systems like Windows. A timeline of DOS operating systems looks like this:
1981 - MS-DOS 1.0
1983 - MS-DOS 2.0
1984 - MS-DOS 3.0
1987 - MS-DOS 4.0
1988 - MS-DOS 5.0
1991 - MS-DOS 6.0
1993 - MS-DOS 6.22
1994 - MS-DOS 7.0
1995 - MS-DOS 7.1
1998 - Windows 98 (which included MS-DOS 7.10)
This timeline shows the different versions of DOS that have been released over the years. MS-DOS was the most popular version of DOS when it was popular, and it started being released in 1981 with the first version, MS-DOS 1.0. MS-DOS kept being released until Windows 98, which was released in 1998 and included the final version of MS-DOS - MS-DOS 7.10. After that, DOS was no longer used and other operating systems like Windows and Mac OS quickly replaced it.