/Zp (Struct Member Alignment)
Controls how the members of a structure are packed into memory and specifies the same packing for all structures in a module.
When you specify this option, each structure member after the first is stored on either the size of the member type or n-byte boundaries (where n is 1, 2, 4, 8, or 16), whichever is smaller.
The available values are described in the following table.
You should not use this option unless you have specific alignment requirements.
You can also use pack to control structure packing. For more information about alignment, see:
To set this compiler option in the Visual Studio development environment
Open the project's Property Pages dialog box. For details, see How to: Open Project Property Pages.
Click the C/C++ folder.
Click the Code Generation property page.
Modify the Struct Member Alignment property.