Add multitasking lie msdos 4.0 or dr dos 7.01

[iw2evk]

Hi,

it's possible implementig multitasking in kernel like ms dos 4.0
https://en.wikipedia.org/wiki/MS-DOS_4.0_%28multitasking%29
or dr dos 7.01?
http://www.drdos.net/documentation/multtask/01mtch1.htm

Thanks
Roberto iw2evk