hvdd (HVDD) - input

      The handle of a VDD returned by a previous call to DosOpenVDD.

    sgid (SGID) - input

      The identifier of a specific DOS session, or null.

    cmd (ULONG) - input

      A function code that is specific to a virtual device.

    cbInput (ULONG) - input

      The length, in bytes, of the application data in pInput.

    pInput (PVOID) - input

      The address of the command-specific information.

      The system sends this data to the virtual device driver to process the specified command.

    cbOutput (ULONG) - input

      The length, in bytes, of pOutput.

    pOutput (PVOID) - output

      The address of the buffer where the VDD returns the information for the specified command.

      This information is specific to the command and the virtual device driver.

    ulrc (APIRET) - returns

      Return Code.

      DosRequestVDD returns one of the following values:

    • NO_ERROR 6
        ERROR_INVALID_HANDLE
      21
        ERROR_NOT_READY
      644
        ERROR_INVALID_CALLER
      For a full list of error codes, see Errors.

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