Microsoft KB Archive/125676

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INFO: New User Heap Limits Under Windows 95

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Q125676

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The information in this article applies to:


 * Microsoft Win32 Software Development Kit (SDK), on platform(s):
 * Microsoft Windows 95

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SUMMARY
In Windows version 3.1, window and menu data is maintained in two 16-bit heaps. This limits window and menu data to 64k each. Windows 95 uses 32-bit heaps for window and menu data, thus greatly expanding the limits placed on the number of items contained in these heaps.

MORE INFORMATION
Windows version 3.1 user and menu heaps are each limited to 64K of data. As a result, the number of window and menus in a system are each constrained to around 200. In Windows 95, the number of Windows and Menus that may exist in the system goes up to 32K each. This is possible because the Windows 95 user and menu heaps are each two megabytes in size.

The first 64K of the user heap looks exactly as it did in Windows version 3.1, except for the absense of WND structures. The Windows 95 WND structures populate the heap space above 64K, thus increasing the number of WND structures the heap can hold. This new arrangement also has the positive effect of freeing up space in the lower 64K space, making more space for class structures and other items that reside in the user heap. For the menu heap, there is nothing special about the low 64K, menus and their data may appear anywhere in the two-megabyte heap.

Additional query words:

Keywords : kbGrpDSUser kbOSWin95

Issue type : kbinfo

Technology : kbWin32SDKSearch kbAudDeveloper kbSDKSearch kbWin32sSearch