INT 21 U - OS/2 v2.1+ Virtual DOS MachineA special type of virtual machine provided by OS/2 version 2.0, in which a copy of MS-DOS or an MS-DOS compatible operating system (or even an incompatible 8086 operating system) is run and appears to have full control of the system. See also Virtual Machine, INT 21h Function 64h. - UNLOAD DOSKRNL SYMBOLS & LOAD PROGR AH = 64h DX = 0006h (function number) CX = 636Ch (magic value, "cl") BX = 0000h (indicates special request) ES:DI -> ASCIZA NUL-terminated ASCII string. The ASCIZ string "ABC" consists of the four bytes 41h, 42h, 43h, and 00h. Unless otherwise specified, maximum lengths given in the interrupt list do not include the terminating NUL. filespec DS = base address for loading Notes: if CX is not 636Ch on entry, INT 21/AH=6Ch is invoked, because a bug in OS/2 1.x FAPI erroneously called AH=64h instead of AH=6Ch this function is only supported by the kernel debugging version of OS2KRNL