INT 21 - COMTROL HOSTESS i/ISA(Industry-Standard Architecture) The expansion bus used by the IBMInternational Busiuness Machines PCIBM PC/ATIBM PC AT.  See also EISA. DEBUGGER - GET SEGMENT FOR CONTROL PROGRAM USE
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Return: AX = first segment available for control program use
SeeAlso: INT 20"COMTROL",INT 22"COMTROL"