I suggest that the tags dos and ms-dos be synonyms of one another. There are 419 questions tagged ms-dos and 1147 tagged dos, with 100 of these tagged both ways.
Most questions that apply to one of these tags apply equally to the other. Users who don't know to check both tags lose out on potentially applicable questions.
(I cannot suggest this in the normal manner because I have reputation in MS-DOS but not DOS.)