Question

what do you mean by 'dose plan'?

Answer 1

MS-DOS was the most commonly used member of the family of disk operating systems. It was the main choice as an operating system for IBM PC-compatible computer systems during the 1980s to mid-1990s. MS-DOS was gradually replaced by system's with graphical user interfaces, particularly Microsoft Windows.

Techopedia explains Microsoft Disk Operating System (MS-DOS)

MS-DOS was originally called 86-DOS. It was written by Tim Patterson (considered the father of DOS) and owned by Seattle Computer Products. Microsoft bought 86-DOS for $75,000, licensed the software and released it with an IBM PC as MS-DOS 1.0 in 1982. MS-DOS was originally designed to run on any computer with an Intel 8086 processor, but the various hardware versions on these computers made compatibility difficult. As a result, Microsft provided hardware equipment manufacturers with a development kit that could be used to tune the MS-DOS operating system for the computer's specific hardware. As a result, there were many versions of MS-DOS. There were also compatibility issues with MS-DOS and IBM where some machines were compatible with MS-DOS but not IBM. These computers could only run programs that were written for MS-DOS and did not depend on any of IBM's peripheral architecture