MS-DOS 1.23

MS-DOS 1.23 was released in 1982, among the first versions of MS-DOS. MS-DOS 1.25 is the first version of MS-DOS released to OEMs but according to a document named  provided by Seattle Computer Products, MS-DOS 1.23 did exist and was possibly released to a small number of OEMs. There is a known evaluation copy of MS-DOS 1.23 licensed to American Science, Energy and Environment.