INT 21 - DR MultiUser DOS 5.0 - API
        AX = 4459h
        CL = function (see INT E0"CP/M")
        DS,DX = parameters
Notes:  DR-DOS 5.0 returns CF set and AX=0001h
        this API is also available on INT E0
SeeAlso: AX=4452h,INT E0"CP/M"

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