DOS was an operating system that appeared shortly after CPM. It was the IBM version of CPM to a degree. (IBM also did make a IBM CPM). Before IBM P.C.'s became the standard we computer geeks used S-100 systems at home with CPM as our operating system. (Don't ask about before that...!)
dos(disk operating system) it is used to run older programs and junk
DOS is not used at any time in any modern operating system.
DOS was discontinued when Windows 95 got relased (1995)
Yes it is used to comment Dos line
"fdisk" command is used for partitioning in DOS.
dos operating system
MS-DOS ended with Windows NT. It used file command.com to interpret all DOS commands. Win 2000, XP, Vista use a DOS Shell which emulates DOS but is not really DOS.
Dos files are the files with the extension .bat which are used for programming in DOS. This is also called as batch file programming.
No Dos is still used in many things today. Many programs are Windows Only due to them using Dos Files.
The BACKUP command is used to backup in DOS 6 plus version.
There are no widely used versions of DOS. It hasn't been used as an operating system since Windows 95 came out. If I recall correctly, the last version of DOS was 7.5 back in the early 1990s.
The Fdisk command is used to change hard disk partitions in DOS.