Microsoft KB Archive/102570

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INFO: DdeCreateStringHandle() lpszString param


The information in this article applies to:

  • Microsoft Windows Software Development Kit (SDK) 3.1
  • Microsoft Win32 Application Programming Interface (API), used with:
    • Microsoft Windows NT Server versions 3.5, 3.51
    • Microsoft Windows NT Workstation versions 3.5, 3.51
    • Microsoft Windows 95


The documentation for the DdeCreateStringHandle() function in the Windows 3.1 Software Development Kit (SDK) "Programmer's Reference, Volume 2: Functions" incorrectly states that the lpszString parameter may point to a buffer of a null-terminated string of any length, when the string is actually limited to 255 characters.

DDEML string-management functions are internally implemented using global atom functions. DdeCreateStringHandle() in particular, internally calls GlobalAddAtom(), and therefore inherits the same limitation as atoms to a maximum of 255 characters in length.


DDEML applications use string handles extensively to carry out DDE tasks. To obtain a string handle for a string, an application calls DdeCreateStringHandle(). This function registers the string with the system by adding the string to the global atom table, and returns a unique value identifying the string.

The global atom table table in Windows can maintain strings that are less than or equal to 255 characters in length. Any attempt to add a string of greater length to this global atom table will fail. Hence, a call to DdeCreateStringHandle() fails for strings over 255 characters long.

This limitation is by design. DDEML applications that use the DdeCreateStringHandle() function should conform to the 255-character limit. This limitation has been preserved on the Windows NT version of DDEML for compatibility reasons.

Additional query words: 3.10 3.50 4.00

Keywords : kbDDE
Issue type : kbinfo
Technology : kbAudDeveloper kbSDKSearch kbWin32sSearch kbWin32API kbWinSDKSearch

Last Reviewed: December 16, 2000
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