INT 21 U - OS/2 v2.1+ Virtual DOS Machine - OS/2 API support
        AH = 64h
        CX = 636Ch ("cl")
        BX = API ordinal (see below)
        other registers as appropriate for API call
          if ordinal 0025h:
                DS:SI -> STARTDATA structure (see below)
Return: as appropriate for API call
          if ordinal 0025h:
                AX = return code

Values for API ordinal:
 0025h  DOS32StartSession
 0082h  DosGetCP
 00A7h  DosQFSAttach
 00BFh  DosEditName
 00CBh  DosForceDelete
 0144h  Dos32CreateEventSem
 0145h  Dos32OpenEvenSem
 0146h  Dos32CloseEventSem
 0147h  Dos32ResetEventSem
 0148h  Dos32PostEventSem
 0149h  Dos32WaitEventSem
 014Ah  Dos32QueryEventSem
 014Bh  Dos32CreateMutexSem
 014Ch  Dos32OpenMutexSem
 014Dh  Dos32CloseMutexSem
 014Eh  Dos32RequestMutexSem
 014Fh  Dos32ReleaseMutexSem
 0150h  Dos32QueryMutexSem
 0151h  Dos32CreateMuxWaitSem
 0152h  Dos32OpenMuxWaitSem
 0153h  Dos32CloseMuxWaitSem
 0154h  Dos32WaitMuxWaitSem
 0155h  Dos32AddMuxWaitSem
 0156h  Dos32DeleteMuxWaitSem
 0157h  Dos32QueryMuxWaitSem

Format of STARTDATA structure:
Offset  Size    Description
 00h    WORD    length of structure (must be 0018h,001Eh,0020h,0032h,or 003Ch)
 02h    WORD    relation of new process to caller (00h independent, 01h child)
 04h    WORD    fore/background (00h foreground, 01h background)
 06h    WORD    trace options (00h-02h, 00h = no trace)
 08h    DWORD   pointer to ASCIZ program title (max 62 chars) or 0000h:0000h
 0Ch    DWORD   pointer to ASCIZ program name (max 128 chars) or 0000h:0000h
 10h    DWORD   pointer to ASCIZ program args (max 144 chars) or 0000h:0000h
 14h    DWORD   "TermQ" (currently reserved, must be 00000000h)
 18h    DWORD   pointer to environment (max 486 bytes) or 0000h:0000h
 1Ch    WORD    inheritance (00h or 01h)
 1Eh    WORD    session type
                00h OS/2 session manager determines type (default)
                01h OS/2 full-screen
                02h OS/2 window
                03h PM
                04h VDM full-screen
                07h VDM window
 20h    DWORD   pointer to ASCIZ icon filename (max 128 chars) or 0000h:0000h
 24h    DWORD   "PgmHandle" (currently reserved, must be 00000000h)
 28h    WORD    "PgmControl"
 2Ah    WORD    initial column
 2Ch    WORD    initial row
 2Eh    WORD    initial width
 30h    WORD    initial height
 32h    WORD    reserved (0)
 34h    DWORD   "ObjectBuffer" (currently reserved, must be 00000000h)
 38h    DWORD   "ObjectBufferLen" (currently reserved, must be 00000000h)

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