| Value | Meaning |
|---|---|
| IOC_UNIX0x00000000 | |
| IOC_WS20x08000000 | |
| IOC_PROTOCOL0x10000000 | |
| IOC_VOID0x20000000 | No parameters. |
| IOC_OUT0x40000000 | Copy parameters back. |
| IOC_IN0x80000000 | Copy parameters into. |
| IOC_VENDOR0x18000000 | |
| IOC_INOUT(IOC_IN | IOC_OUT) | Copy parameter into and get back. |