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BuildCommDCB info  Overview  Group

The BuildCommDCB function fills a specified DCB structure with values specified in a device-control string. The device-control string uses the syntax of the mode command.

BOOL BuildCommDCB(

    LPCTSTR lpDef,

// pointer to device-control string


// pointer to device-control block



Pointer to a null-terminated string that specifies device-control information. The string must have the same form as the mode commandís command-line arguments. For example, the following string specifies a baud rate of 1200, no parity, 8 data bits, and 1 stop bit:
baud=1200 parity=N data=8 stop=1 


The device name is ignored if it is included in the string, but it must specify a valid device, as follows:

COM1: baud=1200 parity=N data=8 stop=1 

For further information on mode command syntax, refer to the end-user documentation for your operating system.

Pointer to a DCB structure to be filled in.

Return Values

If the function succeeds, the return value is nonzero.

If the function fails, the return value is zero. To get extended error information, call GetLastError.


The BuildCommDCB function adjusts only those members of the DCB structure that are specifically affected by the lpDef parameter, with the following exceptions:

The BuildCommDCB function only fills in the members of the DCB structure. To apply these settings to a serial port, use the SetCommState function.

There are older and newer forms of the mode command syntax. The BuildCommDCB function supports both forms. However, you cannot mix the two forms together.

The newer form of the mode command syntax lets you explicitly set the values of the flow control members of the DCB structure. If you use an older form of the mode syntax, the BuildCommDCB function sets the flow control members of the DCB structure, as follows:

See Also

DCB, SetCommState

See also:

file: /Techref/os/win/api/win32/func/src/f03_15.htm, 5KB, , updated: 2001/6/23 20:30, local time: 2022/5/16 23:55,

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