INT 21 - DR Multiuser DOS 5.0 - API(Application Program[ming] Interface) The defined set of calls which a program may make to interact with or request services of the operating system or environment under which it is running. Because the inputs and outputs of the calls are well-defined, a program using the API can continue using the identical calls even if the internal organization of the program providing the API changes. AX = 4459h CL = function (see #04019 at INT E0"CP/M-86One of the three operating systems offered by IBMInternational Busiuness Machines for its original PCIBM PC (the other two were MSDOS and the UCSD p-System). It has since evolved into DR-DOS version 6 and Novell DOS 7.") DS,DX = parameters Notes: DR DOS 5.0 and Novell DOS 7 return CF set and AX=0001h this API(Application Program[ming] Interface) The defined set of calls which a program may make to interact with or request services of the operating system or environment under which it is running. Because the inputs and outputs of the calls are well-defined, a program using the API can continue using the identical calls even if the internal organization of the program providing the API changes. is also available on INT E0 SeeAlso: AX=4452h,INT E0"CP/M-86One of the three operating systems offered by IBMInternational Busiuness Machines for its original PCIBM PC (the other two were MSDOS and the UCSD p-System). It has since evolved into DR-DOS version 6 and Novell DOS 7."