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#define INCL_DOSDEVICES
 
USHORT DosPortAccess(usReserved, fRelease, usFirstPort, usLastPort)
USHORT usReserved;     /* must be zero              */
USHORT fRelease;       /* request/release indicator */
USHORT usFirstPort;    /* first port number         */
USHORT usLastPort;     /* last port number          */
 
The DosPortAccess function requests or releases access to a port, or ports,
for input/output privilege.
 
Parameter    Description
────────────────────────────────────────────────────────────────────────────
 
usReserved   Specifies a reserved value; must be zero.
 
fRelease     Specifies the type of access request. If this parameter is
             FALSE, the function requests access to a port. If it is TRUE,
             the function releases access to a port.
 
usFirstPort  Specifies either a single port or the starting port number
             (start-of-range) in a contiguous range.
 
usLastPort   Specifies either a single port or the ending port number
             (end-of-range) in a contiguous range. If only one port is being
             used, the usFirstPort and usLastPort parameters must be the
             same.
 
Return Value
 
The return value is zero if the function is successful. Otherwise, it is an
error value.
 
Comments
 
Programs that perform input or output (I/O) to a port, or ports, in IOPL
segments must request port access from the operating system.
 
Granting port access automatically grants cli and sti privileges from the
operating system. Therefore, there is no need to make an additional call to
the DosCLIAccess function.
 
See Also
 
DosCLIAccess
 
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